EP0901575A1

EP0901575A1 - High pressure pump for all liquids

Info

Publication number: EP0901575A1
Application number: EP97926060A
Authority: EP
Inventors: Louis-Claude Porel
Original assignee: Hydro Rene Leduc SA
Current assignee: Hydro Leduc SAS
Priority date: 1996-06-07
Filing date: 1997-05-30
Publication date: 1999-03-17
Anticipated expiration: 2017-05-30
Also published as: EP1048849A1; WO1997047883A1; JP2000511989A; DE69732802T2; EP0901575B1; US6264437B1; DE69732802D1; ES2238968T3; EP1048849B1; JP3990732B2; PT1048849E

Abstract

The invention features a device that enables the pumping of any kind of liquid while giving it a very high delivery pressure. The units (24, 44) that cause pumped liquid suction and then its delivery are driven exclusively by hydraulic means excluding mechanical means. So that there is no material contact between the said driving units and the pumped product and that the said product cannot damage the said mechanical driving units, the chamber receiving the hydraulic fluid is, at the end of each compression cycle, placed again in direct communication with the hydraulic fluid reservoir.

Description

HIGH PRESSURE PUMP FOR ALL LIQUIDS

The present invention relates to a pump capable of pumping and pumping under high pressure virtually any liquid such as: water, petrol, diesel, oils, corrosive chemical liquids and sludge; but more particularly for the high pressure supply of fuel injectors for internal combustion engines.

Low pressure pumps for this kind of liquids are known, they are generally centrifugal pumps, with enqrenageε, sometimes with pistons or others, but with these known pumps, it is impossible, if not very difficult and expensive, d '' obtain a high discharge pressure (greater than 50 bars), because, as soon as high pressures are approached, seizures of the moving parts and significant leaks occur, due to the often very low viscosity of the fluids pumps.

To avoid such seizures or such leaks, it is known to use diaphragm pumps, but it is then impossible to obtain a high discharge pressure. Indeed, the membrane is on one side driven by mechanical means (cam, lever or the like) and is on the other subject to the discharge pressure: it follows that, as soon as the pressure becomes high the membrane deteriorates at the points of application of the mechanical forces.

It is also known, for pumping particular liquids such as for example corrosive liquids, to associate two pumps: a first pump which is a hydraulic pump which pumps and sucks up hydraulic liquid which drives the movable elements of the machine alternately. 'a second pump, the latter sucking and pressurizing the liquid to be pumped. These mobile elements which provide the physical separation between the hydraulic fluid and the fluid to be pumped, while being driven by an alternating movement by the hydraulic fluid, are either deformable membranes or free pistons.

The free pistons have a defect with regard to tightness, a defect which is unavoidable in cases where one must have an absolute seal. If a seal is placed between the free piston and the cylinder in which it moves, it is not possible to obtain a perfect seal. If the seal is removed: either there is a very thin film of oil between the friction surfaces and therefore micro-leaks; or there is no oil film and the friction surfaces will heat up. In the particular case of high-pressure petrol injection, no leakage, however small, is admissible and, obviously, any heating may cause an explosion.

Known devices with free pistons, such as for example the US patent 4,443,160 are therefore to be avoided.

The present invention therefore relates to a pumping device in which the mobile elements, driven by an alternating pumping movement by the hydraulic pump and ensuring a completely sealed separation between the "motor" hydraulic liquid and the liquid to be pumped are deformable membranes.

In general, pumps of this type with deformable membranes have at least one, if not several, of the following drawbacks: a - if the separation and pumping membrane is mechanically linked to the piston of the hydraulic pump, there is no pressure on each side of the flexible membrane and the latter does not hold over time, it deteriorates;

b - if the diaphragm is completely free, that is to say it is not linked to any drive mechanism and is driven only by the hydraulic liquid pumped by the pump, there is pressure between the two ribs of the diaphragm . However, due to the inevitable leaks, even very small, the volume of hydraulic pumped fluid increases with each cycle and eventually becomes larger than that which the membrane can pump: there then occurs a hydraulic blockage creating an overpressure such as either of the two pumps breaks. In the particular case of the injection of high pressure petrol, if it is the element which delivers the high pressure petrol which breaks, the fire is inevitable;

c - In one case as in the other, that is to say that the membrane is linked to the piston or else free, if the volume of hydraulic liquid which is continuously discharged and re-aspirated is always the same, it will heat up due to the indefinitely repeated compression cycles, until reaching a temperature such that the membrane (s) will be destroyed.

In US Pat. No. 4,392,787 NOTTA, an assembly has been described comprising a hydraulic pump with bias plate, each piston of the pump being associated at its end with a flexible membrane which is connected to a rod sliding inside the piston. This device has the faults described above in "a" and "c". The volume of liquid pressurized continuously is always the same and will therefore heat up. On the other hand, the inevitable small leaks are compensated by admission of oil in addition by a non-return valve, but if accidentally a significant leak occurs, the piston comes into mechanical contact with the membrane which will then be destroyed.

In US Patent 2,960,936 DEAN, a pump has been described in which a completely free membrane is cyclically crushed and released by a hydraulic volume implemented by a piston actuated by a cam. This device has the faults "b" and "c". If, for any reason, the supply stops or even slows down, the membrane will not redeploy completely and a corresponding quantity of hydraulic fluid will be introduced during each cycle until it breaks (disadvantage " b "). On the other hand, as it is always the same volume of hydraulic liquid which is compressed, 1 heating is inevitable (drawback "c").

German patent 2,447,741 WANNER describes a diaphragm pump which is mechanically linked to a piston which slides inside a hydraulic pump piston. The disadvantages are the same as for US Pat. No. 4,392,787 cited above.

To eliminate these drawbacks, the present invention provides a device in which each membrane is free and in which, at the end of each cycle of a piston, the dead chamber, located downstream of the top dead center of this piston (compression position maximum), in which the liquid in contact with the membrane is placed, is placed in communication with the hydraulic fluid reserve; so that the liquid which is there is pushed back towards this reserve first by the expansion of the liquid, then by effect of pushing back by the membrane which is constrained by a spring.

On the one hand, a continuously repeated heat exchange between the compressed liquid and one that is not and, on the other hand, a return to the initial position of the membrane at each cycle or, in other words, an elimination of any increase in the volume of hydraulic fluid, acting on the membrane, increase which is inevitably permanently caused by leaks; because it is not possible to realize a high pressure hydraulic pump with pistons, which does not heat and which has a good performance, without leaks.

According to a first object, the present invention relates to a pump making it possible to pump any kind of liquid while imparting to it a very high discharge pressure, of the type constituted by the association of two pumps: on the one hand, a pump hydraulic; on the other hand, a second pump whose mobile means, carrying out the suction and the delivery of the liquid to be pumped, are flexible membranes driven by an alternating movement in one direction more in the other by the displacement of the hydraulic liquid pumped then re-aspirated by the first pump characterized in that the pistons of the first pump are hollow and traversed by the hydraulic liquid which, during the suction phase passes through a lunula or groove dug in the face of the bias or cam plate; the deformable membranes being each constrained by a spring so that at the end of the compression stroke of each piston, communication is established between the chamber where the hydraulic liquid is forced against the membrane and the suction chamber, this liquid being, on the one hand, sucked in by the movement of the piston and discharged by the membrane under the action of its spring, which ensures: on the one hand an exchange between the hydraulic liquid heated by compression and the liquid not heats and, on the other hand, a return to the initial position of the membrane. The pump according to the invention can also include one or other of the following provisions:

a - the second pump has as many volumes or bores as the first pump has bores, each bore of the second pump communicating directly with the corresponding bore of the first pump so that each piston of the first pump delivers and aspirates cyclically hydraulic fluid in the corresponding bore of the second pump.

b - each bore of the second pump is divided into two parts by a deformable membrane counter-clamped by a spring, the part communicating with the corresponding bore of the first pump and receiving the hydraulic fluid discharged and re-sucked by it, the other part, fitted with suction and discharge valves, suction and delivery of the product to be pumped.

c - the chamber in which the heads of the pistons are struggling is connected to a reservoir of hydraulic fluid.

d - the hydraulic fluid reservoir is external to the first pump and communicates with the latter by a pipe opening into the chamber.

e - the pump according to the invention is intended for supplying fuel injectors for internal combustion engines under high pressure, the hydraulic fluid of the first pump (I) possibly being the oil of said engine.

According to a second object, the present invention relates to means making it possible to vary the displacement of the first pump and therefore the fuel flow rate to the injection devices.

These means are: either the arrangement of a tilting platform with variable inclination, or the arrangement of means in the pistons of the hydraulic pump, having the function of short-circuiting all or part of the volume of hydraulic fluid introduced into the bore during the suction phase.

According to the invention, each hollow piston of the hydraulic pump is provided with openings which can be concealed in whole or in part by a movable jacket, all the movable shirts being moved together by a control member controlled by the operating conditions of the engine.

This device may also include one or other of the following provisions:

a - the pistons slide in two supports pierced with orifices, these two supports being separated from each other by an annular space, constituting a chamber, in which the liners move between two extreme positions, one for which the orifices not being masked by the liners all the liquid discharged by each piston back into the annular chamber through the orifices of the pistons the flow rate of the pump (I) being zero: the other for which all the orifices being masked by the liners each piston delivers all of the hydraulic fluid drawn in, the pump flow rate then being maximum.

b - the liners can occupy all the intermediate positions between the two extreme positions; so that the pump flow (I) can be regulated for all values between a zero flow and a maximum flow.

c - the liners are coupled to a common control member which is controlled by any suitable control device to regulate the flow of gasoline at high pressure according to the supply needs of the engine without high pressure gasoline being returned to the tank.

d - a damping device can be arranged downstream of the outlet of the second pump (II) and upstream of the injectors to cancel the pulsation effect caused by the first pump (I).

e - the damping device can be a large volume capacity in relation to the fuel flow rate, maintained under the injection pressure by any appropriate means and behave substantially like a hydromechanical accumulator.

By way of nonlimiting examples and to facilitate understanding of the invention, the accompanying drawings show:

- Figure 1, a longitudinal sectional view of a first embodiment of the invention.

- Figure 2, a cross-sectional view along A-A of Figure 1.

- Figure 3, a longitudinal sectional view of the double pump with variable flow, the parts being in the position for which the flow is maximum.

- Figure 4, a view of the double pump of Figure 3, the parts being in the position for which the flow is zero.

- Figure 5, a view along A-A of the face of the bias plate of Figures 3 and 4.

- Figure 6, a longitudinal sectional view of the pump of Figure 1 in which the individual membranes have been replaced by a single membrane.

- Figure 7, a sectional view along AA of Figure 6. - Figure 8, a sectional view along BB of Figure 6.

Figure 9, a longitudinal sectional view of an alternative embodiment of the pump according to the invention in which the suction valves have been removed.

- Figure 9a, a detail view of Figure 9, on an enlarged scale.

- Figure 10, a longitudinal sectional view of the pump of Figure 6 provided with the suction system by the membrane of Figure 9.

- Figure 11, a view of an alternative embodiment in which the hydraulic pump is a radial pump.

Referring to Figures 1 and 2 we see that the device according to the invention comprises a first pump, designated by the general reference I and a second pump, designated by the general reference II.

The first pump I is a pump with axial pistons driven in an alternating movement back and forth by a bias plate 1.

The bias plate 1 is integral with a motor shaft 2 (driven by any means not shown) carried by bearings 3. A plurality of hollow pistons 4 bear against the oblique face of the plate 1 each by means of a sliding stud 5, which is pierced in its center with a bore 6. Each piston 4 is held by a spring 7 against its stud. On the front face 1 is engraved a lunula 8. When the shaft 2 is rotated, the bias plate 1, the studs 5 and the spherical heads 4a of the pistons 4 struggle in a chamber 9. This chamber 9 opens, by a plurality of holes 22, passing through the body 21 of the pump I, in a reservoir 11. This reservoir 11 is constituted by a cylindrical envelope 23 which surrounds the body 21. When the motor shaft 2 rotates, the face of the bias plate 1 oscillates in the chamber 9 so that the pistons 4 are moved back and forth: in the direction which corresponds to the suction, the pistons 4 are moved by their spring 7; in the other direction which corresponds to the delivery under pressure, they are pushed back against the spring 7 by the bias plate 1. During the suction phase, the hydraulic fluid which is in the chamber 9 penetrates to the inside of the pistons 4 passing through the lunula 8 and the bore 6 of the studs 5.

This type of pump is known and described in numerous prior patents belonging to the applicant.

When the hydraulic pump I is used in a known manner, each bore 12 in which a hollow piston 4 slides has at its end a non-return valve; so that all of said pistons 4 causes a flow under pressure (and even at high pressure since it can exceed 1000 bars with this type of pump).

However, in the context of the present invention, none of the bores 12 in which the pistons 4 slide have a non-return valve.

A pump II is associated with the pump I immediately downstream of the latter.

Each bore 12 of the pump I, in which a piston 4 slides, corresponds, in the pump II, a chamber or bore 13 divided into two parts 13a and 13b by a flexible membrane 24 supported by a spring 15. The part 13a communicates directly with the end of the bore 12, while the part 13b is provided at its end opposite to the membrane 24 with a suction valve 16 and a discharge valve 17. All the valves 17 flow into a common pipe 18.

Preferably, as shown, each spring 15 bears on the rear face of the membrane 24 by means of a cup 20. The shape of the cup 20 is determined so that the support of the cup 20 on the rear face of the membrane 24 does not cause any deterioration thereof.

The operation is described below:

When the drive shaft 2 is driven, the pistons 4 discharge the hydraulic fluid into the chambers 13. The hydraulic fluid discharged into the part 13a of the chamber 13, bears on the front face of the diaphragm 24 and causes displacement of that -ci, in the direction of the arrow fl (fig.l). By moving this membrane 24 discharges the liquid contained in the part 13b of the chamber 13. This discharge takes place through the non-return valve 17.

Then when the bias plate 1 continues to rotate, the stud 5 of each piston 4 passes over the lunula 8 which puts the chamber 13a, the interior of the hollow piston 4 and the suction chamber 9 in communication. At the very start of the stroke of the stud 5 on the lunula 8 the liquid under high pressure which is in the chamber 13a relaxes in the direction of the chamber 9; then under the action of the spring 7 of the piston 4 and of the spring 15 of the membrane 24 the liquid located in the chamber 13a is discharged into the bore 12 and from there towards the chamber 9.

Thus the hydraulic fluid, which is in the dead chamber at the end of each bore 12 when the piston 4 is at the end of its compression stroke and in the chamber 13a, is renewed at the end of each compression cycle , which avoids everything heating of this liquid, which would otherwise be inevitable. In addition, this return to direct communication between the chamber 13a and the chamber 9, and this at each cycle, achieves a return to the initial position of the movable elements so that the volume of hydraulic liquid discharged into the chamber 13a remains strictly equal to it. -Even, the inevitable leaks from the hydraulic pump being returned to the chamber 9. This connection of the chambers 9 and 13a therefore eliminates the drawbacks described above in

The displacement of the membrane 24 in the direction of the arrow f2 has the effect of sucking the product to be pumped into the part 13b of the bore 13, through the non-return intake valve 16 and of discharging the hydraulic fluid found in part 13a.

Thus the product to be pumped is alternately sucked in and then discharged by the reciprocating movement of the membranes 24, this movement being caused by variations in the volume occupied by the hydraulic liquid in the parts 13a of the bores 13, these variations in volume being caused by the alternations of hydraulic fluid delivery and suction by the pistons 4 of the first pump I.

Each membrane 24 is subjected, on its two front and rear faces and this uniformly distributed over the entire surface of the membrane, to the same pressure: on one side the pressure of the hydraulic motor fluid, on the other the pressure of the pumped liquid. The membrane therefore does not undergo any mechanical stress and therefore cannot tear.

The pump according to the present invention is therefore a diaphragm pump in which each diaphragm is, in the delivery phase, in equipression on each side, which makes it possible to have a delivery pressure equal to the hydraulic pressure that the first pump I.

The pump according to the present invention can be used, inter alia, to pressurize liquids having no greasing power. In particular, it can be used to supply injectors for internal combustion engines (car engines) supplied with super-fuel and / or liquid LPG as a substitute fuel for example. The super-fuel is sucked in by the valves 16, discharged under high pressure (more than 50 bars) by the valves 17 without the fuel ever being brought into contact with metal members that have to slide against each other.

It should be noted that at high pressures, liquids can no longer be considered incompressible. When a piston 4 is at the end of the delivery stroke, the pressure of the hydraulic fluid is at its maximum. As has been said above, when the stud 5 is located on the start of the lunula 8 the liquid, while expanding will discharge through the piston 4, the passage 6 of the stud 5 and the lunula 8 in the chamber 9; then it will be driven back by the action of the spring 15. The compressed liquid is hot while the liquid in the chamber 9 and the tank is not: there will therefore be a small exchange of liquid heated by the compression and unheated liquid which will ensure thermal equilibrium of the first pump I. Preferably, although this is not shown the cylindrical envelope 23 of the tank can be provided with cooling fins.

In the case where the double pump according to the invention is used, as indicated above, for the high pressure supply of fuel injectors for engines, the engine oil itself can advantageously be used as hydraulic fluid by having the chamber 9 communicate directly with the engine oil distribution circuit, the temperature of this oil being regulated by the appropriate engine members.

The pump according to the invention can also be used to circulate drilling mud under pressure.

It can in fact be used to pressurize any liquids, including corrosive or aggressive liquids.

In the case where the hydraulic stage, pump I, is confronted with a liquid of high viscosity, as is the case with cold use, for example, it is preferable, as is known, to have the means mechanical holding the heads 4a of pistons 4 on their pads 5 during the suction phase.

As explained above, the suction force of the second pump II, which is linked to the power of the springs 15, allows the membranes 24 to return to their initial position, due to the communication with the chamber 9.

If this initial reset, permitted by this communication with the hydraulic fluid reserve, were not made, there could be a slight drift at each revolution of the pump.

This drift would quickly cause a difference in volumes between the bore 12 and the portion 13a of the corresponding bore 13, which in turn would quickly cause the membranes 24 to come into abutment and immediately cause the pump to rupture (i.e. at pump I or at pump II). It therefore appears that this reset, or reset to the initial position of the mobile elements 24 of the second pump II, via the lunula 8 is essential.

Figures 3 to 5 relate to an improvement to the device of Figures 1 and 2 by means of which it will be possible to vary at will the flow rate of the liquid to be pumped.

When this liquid is petrol intended to supply an engine, it may be advantageous to vary the volume of petrol pumped by pump II in order to adapt it to the operating conditions of the engine.

In order for a motor to be able to run at full speed, the displacement of the pump must be determined according to the extreme conditions of use of the motor, namely: operation at maximum speed and full load. This therefore defines a maximum flow rate of the pump which is supplied continuously; so that, outside of these extreme conditions of use, the pump provides an excess flow, which is returned to the tank.

But the gasoline thus returned to the tank is found to have been heated by compression, so that hot gasoline is constantly returned to the tank. As the tank empties the gasoline becomes increasingly hot so that it may appear in the tank of unwanted gasoline vapors whose treatment is made difficult by standards more and more severe especially with regard to direct injection petrol engines.

It therefore becomes necessary to modulate the pump flow according to the requirements of the motor. The first solution consists in producing the first pump I, in the form of a variable flow pump using a bias plate 1 with variable inclination as is done in certain pumps produced by the applicant.

However, such a pump risks being too expensive for mass production of cars; so a second solution is described below.

The device according to this second solution is characterized in that it comprises a double pump such as that described in patent application 96.07043, but in which each piston of the hydraulic pump is provided with means making it possible to cancel all or part the flow pumped by said piston.

Figures 3 and 4 describe a double pump similar to that of Figures 1 and 2 in which the same elements have the same references.

Referring to these figures, it can be seen that each hollow piston 4 is traversed right through by a pipe 30.

On the other hand, the pistons 4 are carried by two supports 31 and 32 pierced with orifices in which said pistons slide. The holes drilled in the support 31 are designated by the reference 33, while the holes drilled in the support 32 constitute the cylinders 12 mentioned above. For this purpose, the thickness of the support 32 is greater than the maximum stroke of the pistons 4.

The space between the supports 31 and 32 constitutes an annular chamber 35.

In this space 35 each piston 4 is partially covered by a sliding jacket 34. These sliding shirts are all connected to a connecting rod control 38 so as to be able to slide all together between two extreme positions, the first being illustrated in FIG. 3, the second being illustrated in FIG. 4.

In the position shown in FIG. 3, said shirts 34 obscure the holes 36 which make the internal pipe 30 of each piston 4 communicate with the annular chamber 35. In the position shown in FIG. 4, the shirts 34 reveal said holes 36.

The springs 7 of FIGS. 1 and 2, which have the function of keeping the heads of the pistons in abutment against their sliding stud 5 are replaced by a pusher 7b which acts on a collar 6 which is supported on the rear of each head of piston 4. The pusher 7b is constrained by a spring 7a.

The pusher 7b, contretenant the flange 6 of each piston head is crossed by a pipe 37 which communicates between them the two chambers 9 and 35.

Thus when, under the effect of the control rod 38, the liners 34 are in the position shown in FIG. 4, the hydraulic liquid discharged by each piston 4 flows back through the pipes 30 and 36 into the annular chamber 35, and , from there, through the hole 37, in the chamber 9. It follows that the flow rate of the hydraulic pump I is zero, therefore that the membranes 24 are not driven by any movement and exert no pumping action and delivery under fuel pressure to the injectors: the fuel flow to the injectors is therefore also zero.

When, under the effect of the command 38, the liners 34 are in the position shown in FIG. 1, the holes 36 are obscured by said liners and the flow rate of the hydraulic pump I is maximum. It As a result, the fuel flow to the injectors is also maximum.

Between these two extreme positions all the intermediate flows can be obtained as a function of the position of the liners 34, a position determined by the position of the connecting rod 38 which is controlled by the operation of the engine by any suitable control device.

As a result, the output flow rate of the pump II is regulated as a function of the gas flow rate which is necessary for injection and that the excess gasoline returns to the tank are reduced to the maximum.

It should be noted, however, that the fuel flow rate thus obtained is a pulsed flow rate. Indeed, if for example, the liners 34 are in a position such that only 10% of the maximum flow rate of the pump I is delivered in the part 13a of the volume 13, this means that this pump I does not provide any flow rate for 90% of the stroke of each piston or that there is flow only over 10% of the stroke of each piston. This has the effect that the flow is a pulsed flow.

This results in a drawback which must be eliminated.

For this purpose, there is available downstream of the outlet 29 and upstream of the injectors a device eliminating these pulsations. This device can advantageously be constituted in a similar manner to a hydraulic accumulator, that is to say constituted by a capacity having a large volume relative to the flow rate supplied to the injectors and maintained under constant pressure.

This gives an injection flow corresponding exactly to the petrol needs of the engine, without return to the reservoir, this flow being regular, that is to say without pulses.

FIG. 6 represents a pump similar to the pump of FIG. 1, in which the same elements have the same references.

The reservoir 11 of FIG. 1 which envelops the hydraulic pump is replaced by an external reservoir 11a; for the rest, all the components are identical with the only exception of the diaphragm of pump II of FIG. 1.

In the pump of FIG. 1, each volume 13 is divided into two parts 13a, 13b by a membrane 24 pushed back by a spring 15 bearing on the membrane 24 by means of a cup 20.

In the pump of FIG. 6, the individual membranes 24 are replaced by a single membrane 44, which, at the locations of the chambers 13 will deform to partially penetrate said volume 13 against the corresponding spring 15.

More precisely, the pump of FIG. 6, like that of FIG. 1, comprises a one-piece pump casing 40, in two cylindrical parts 40a and 40b, the part 40b having an internal diameter greater than that of the part 40a. In part 40a are arranged the bearings 3, the drive shaft 2, the bias plate 1, the supply chamber 9 and the rear part 41a of a part 41 in which the bores are drilled 12. The front part 41b of this part is located in the upper diameter portion 40b of the casing 40; so that this front part 41b rests against the shoulder which separates the two parts 40a and 40b of the casing 40. The bores 12 of the pistons 4 open out at the front face of this part 41b. A circular plate 42 is disposed against said part 41b and is immobilized in position relative to the latter by a pin 42a. This plate 42 has as many holes 43 as there are bores 12 and chamber 13. The chambers 13 are formed in a part 45 which is screwed to the open end of the part 40b of the casing 40. Between the part 45 and the plate 42 is arranged a membrane 44 which has the shape of a disc having the same diameter as the plate 42. The membrane 44 is pinched between the plate 42 and the end of the part 45. Each bore 43 communicates with a bore 12 of the pump I and is located opposite a volume 13.

When a piston 4 will discharge hydraulic fluid under high pressure, this liquid will be forced out of the bore 12, into the bore 43 and will deform the part of the membrane 44 which is located opposite the corresponding chamber 13, deformation which takes place against the spring 15 bearing against the other face of the membrane 44 by the cup 20. The liquid to be pumped being in the chamber 13 (behind the cup 20) is discharged by the non-return valve back 17. When the piston 4 moves back in its bore 12, the part of the membrane 44 which had deformed, had partially entered the volume 13, is pushed back by the spring 15 and returns to its initial shape by sucking the liquid to be pumped by the non-return valve 16.

As in the previous cases, there is direct communication between the bore 43 and the chamber 9 by the lunula 8.

FIG. 9 represents an alternative embodiment of the pump of FIGS. 6 to 8.

In this variant, the essential difference relates to the mechanical constitution of the hydraulic pump I. This hydraulic pump I comprises, like the pumps of FIGS. 1, 3 and 6, a bias plate 1 against which rest hollow pistons 4 by means of sliding studs 5, pierced with a bore 6 intended to overlap a lunula 8. But in the pumps described above, the bias plate 1 is disposed at the end of a motor shaft 2 carried by bearings 3; while in the pump of Figure 9, the bias plate 1 is integrated in a ball bearing.

This ball bearing comprises an outer cage 61 fixed inside the casing 60 of the pump and an inner cage 62 to which the bias plate 1 is fixed, a set of balls 63 being disposed between the two cages 61 and 62. A its rear part, the bias plate 1 comprises a housing 64 into which the end of a motor shaft, not shown, can fit.

The pump II is identical to that described in relation to FIG. 6, the same elements bearing the same references.

The only difference is that the suction check valves 16 are omitted and that it is the diaphragm 44 itself which is used to fulfill the role of the check valves.

Referring to FIG. 9a, which is an enlarged view of part of FIG. 9a, it can be seen that: each chamber 13 is associated with a conduit 50 connected to a chamber 51 where the liquid to be pumped arrives via a conduit 52 The duct 50 is pierced through the mass of the part 45 and opens, at its end opposite the chamber 51 against the membrane 44. The plate 42 which is interposed between the part 41, in which the bores 12 of the pistons are formed 4 and the part 45, in which the chambers 13 are formed, comprises two housings 53 and 54 connected by a pipe 55. The housing 53 is hollowed out in the face of the part 42 which is in contact with the membrane 44; while the housing 54 is hollowed out in the face which is in contact with the part 41. The housing 54 has a configuration such that it communicates with the bore 12; and the housing 53 reaches up to the level of the chamber 13.

Thus, when the pressurized liquid is discharged by a piston 4, the pressurized liquid arrives through the housing 54 and the pipe 55 in the housing 53 and the membrane is applied by hydraulic pressure against the orifice of the pipe 50 which is thus closed. On the other hand, when the piston 4 is in the suction phase, the movement of the cup 20 which pushes the membrane 44 releases the latter from the orifice of the pipe 50. The membrane 44 being pressed against the bottom of the housing 53, this emerges between the membrane 44 and the wall of the part 45 a space 56 which ensures communication between the pipe 50 and the chamber 13 and thus allows the admission into this chamber 13 of the liquid to be pumped.

It is preferable that the liquid to be pumped (which is for example petrol) arrives via the pipe 52 at a low pressure, of the order of 1 to 2 bars, given by an electric pump of known type, so that , as soon as the hydraulic pressure disappears in the housing 53, the membrane 44 is pushed back to clear the passage 56.

It is also preferable that at the place of each pipe orifice 50 the membrane 44 be provided with a reinforcement cup 57, of a diameter greater than that of the orifice, the object of which is to prevent the membrane is pushed by the pressure in the orifice of the pipe 50 and thus deteriorated. It is also advantageous to shape the membrane by molding so that at rest, in the absence of any pressure, it fills the housing 53 and clears the passage 56.

Thus, the membrane 44 is deformed between a position where it is at the bottom of the housing 53 and a position where it closes the suction duct 50 acts as a non-return suction valve.

There are, of course, as many conduits 50, housing 53, conduit 55, housing 54 as there are bore 12 and chamber 13.

The arrangement thus described in relation to FIGS. 9 and 9a is independent of the configuration of the hydraulic pump I and can be transposed in the pump of FIGS. 6 to 7 as shown in FIG. 9.

In all the examples shown in FIGS. 1 to 9, the hydraulic pump I is a swash plate or bias plate pump and the pistons are axial pistons.

But it should be noted that the same result can be obtained with a radial piston pump on the essential condition that the pistons are hollow and that their heads rest on the drive cam (playing the same role as the plate bias 1) by sliding studs overlapping a lunula; so that at the end of each compression cycle the chamber in which the membrane moves is placed in direct communication with the hydraulic fluid intake chamber.

Such a radial piston pump is shown in FIG. 11. This pump comprises a cam 101, which is an eccentric carried by a motor shaft 102, carried by bearings 103. Each piston is a hollow piston 104 counterbalanced by a spring 107, so that its head 104a is in abutment against the cam 101 by means of a sliding stud 105 crossed by an orifice 106. The cam 101 struggles in a chamber 109 communicating with a reservoir of hydraulic liquid (not shown). The communication between the chamber 109 and the interior of each hollow piston 104 is established when the stud 105 overlaps the groove 108 dug in the cam 101.

The pump II is identical to that of FIG. 1, the same elements bearing the same references.

The cam 101 corresponds to the bias plate 1; pistons 104 to pistons 4; the pads 105 to the pads 5; the groove 108 at the lunula 8 and the chamber 109 at the chamber 9.

The operation of the double pump (I-II) shown in FIG. 10 is identical to that of the pumps previously shown.

Claims

1. Pump making it possible to pump any kind of liquid while imparting to it a very high discharge pressure, of the type constituted by the association of two pumps: on the one hand, a hydraulic pump (I); on the other hand, a second pump (II) whose mobile means, performing the suction and the delivery of the liquid to be pumped, are flexible membranes driven by an alternating movement in one direction

10 then in the other by the displacement of the hydraulic fluid pumped then re-aspirated by the first pump (I) characterized in that the pistons (4, 104) of the first pump (I) are hollow and traversed by the hydraulic fluid which , during the aspiration phase,

15 passes through a lunula (8, 108) hollowed out in the face of the bias plate (1) or cam (101); the deformable membrane (24, 44) being constrained by a spring (15) so that at the end of the compression stroke of each piston (4, 104), the communication

⁹ 0 is established between the chamber (12-13) where the hydraulic liquid is discharged against the membrane ⁽ 24, 44) and the suction chamber (9, 109), this liquid then being, on the one hand, sucked by the movement of the piston (4, 104) and, on the other hand, driven back by the

? 5 membrane (24, 44) under the action of its spring (15) which ensures both: an exchange between the hydraulic fluid heated by compression and the unheated liquid; and a return to the initial position of the membrane (24,44).

2. Pump according to claim 1 in which the first pump (I) or hydraulic pump is a bias plate pump (1) and with axial pistons ⁽ 4) said axial pistons being hollow and constrained by springs (7, 7a) so that the head (4a) of each

35 hollow piston (4) either in abutment against the bias plate (1) by means of a sliding stud (5 ⁾ crossed by a central bore (6), this stud overlapping a lunula (8) engraved on the face of the bias plate (1) during the suction phase of the corresponding piston, so as to establish, during this phase, direct communication between the chamber (9) where the bias plate (1) struggles and the chamber (13a) into which the hydraulic fluid was discharged during the compression phase.

3. Pump according to claim 2 wherein the bias plate (1) is fixed in the inner cage (62) of a ball bearing (63) the outer cage (61) being directly fixed in the housing.

4. Pump according to claim 1 wherein the first pump (I) or hydraulic pump is a radial piston pump (104) driven by a cam (101); said radial pistons (104) being hollow and constrained by springs (107) so that the head (104a) of each hollow piston (104) bears against the cam (101) by means of a sliding stud (105) crossed by a central bore (106), this stud overlapping a groove (108) etched on the surface of the cam (101) during the suction phase of the corresponding piston, so as to establish during this phase a communication direct between the chamber (109) where the cam (101) struggles and the chamber (13a) into which the hydraulic fluid was discharged during the compression phase.

5. Pump according to claim 2 and 3 wherein the second pump (II) has as many chambers or bores (13) as the first pump (I) has bores (12), each chamber (13) of the second pump (II) communicating directly with the corresponding bore (12) of the first pump (I) so that each piston (4, 104) of the first pump (I) delivers and cyclically sucks the hydraulic fluid into the corresponding chamber (13) of the second pump (II).

6. Pump according to claim 5 in which each bore (13) of the second pump (II) is divided into two parts (13a, 13b) by a deformable membrane (24) supported by a spring (15), the part (13a ) communicating with the corresponding bore (12) of the first pump (I) and receiving the hydraulic fluid discharged and re-aspirated by it; the other part (13b), provided with suction (16) and discharge (17) valves, sucking and discharging the product to be pumped.

7. Pump according to claim 6 wherein each spring (15) bears on the rear face of the corresponding flexible membrane (24) via a cup (20) shaped so as not to cause deterioration of said rear face of the membrane (24).

8. Pump according to any one of the preceding claims, in which the chamber (9, 109) in which the heads (4a, 104a) of the pistons (4, 104) are struggling is connected to a reservoir of hydraulic liquid.

9. Pump according to claim 8 wherein the reservoir (11) of hydraulic fluid is external to the first pump (I) and communicates with the latter by a pipe (10) opening into the chamber (9).

10. Pump according to claim 8 wherein the reservoir (11) is constituted by a cylindrical envelope (23) surrounding the body (21) of the first pump and communicating with the chamber (9) by a plurality of orifices (22) .

11. Pump according to claim 2 wherein the individual deformable membranes (24) are replaced by a single membrane (44) interposed between the bores (12) of the pistons (4) and the chambers (13).

12. Pump according to claim 11 wherein a circular plate (42) is interposed between the part (41) in which are formed the bores (12) and the part (45) in which are formed the chambers (13) this part making communicate by holes (43) each bore (12) with the chamber (13) which corresponds to it.

13. Pump according to claim 11 in which in each chamber (13) is arranged a spring (15) which bears on the membrane (44) by means of a coupe1le (20).

14. Pump according to claim 13 wherein each chamber (13) is associated with a non-return suction valve (16) and a discharge non-return valve (17).

15. Pump according to claim 13 wherein each chamber (13) is only associated with a discharge check valve (17), the suction check valve (16) being removed and its function fulfilled by the membrane (44) itself.

16. Pump according to claim 15 wherein the inlet pipe (50) of the liquid to be pumped opens against the membrane (44) which is held in abutment against the orifice of this pipe during the delivery phase and is moved away from it during the suction phase.

17. Pump according to claim 16 in which the part of the membrane (44) which bears against the liquid inlet orifice (50) is provided with a reinforcement cup (57).

18. Pump according to claim 16 in which, during the suction phase, the membrane (44) comes

5 at the bottom of a housing (53) in order to clear a communication passage (56) between the liquid inlet pipe (50) and the chamber (13).

19. The pump of claim 18 wherein the membrane (44) is preformed molding to occupy the

10 bottom of the housing (53) during suction to clear the passage (56).

20. Pump according to any one of the preceding claims, characterized in that it is intended for supply under high pressure

15 of fuel injectors for internal combustion engines, the hydraulic fluid of the first pump (I) possibly being the oil of said engine.

21. Pump according to claim 20, characterized in that it comprises means for varying

20 the flow rate of the hydraulic pump (I) and, consequently, the flow rate of the pump (II) so as to adapt the flow rate of high-pressure pump gasoline to the injectors to the operating conditions of the engine.

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22. Pump according to claim 21 wherein the bias plate (1) of the hydraulic pump (I) is a variable tilt plate.

23. Pump according to claim 21, characterized in that each piston (4) of the hydraulic pump 30 (I) is provided with openings (36) which can be concealed, in whole or in part, by a movable jacket (34 ), all the movable folders (34) being moved together by a control member (38) controlled by the operating conditions of the engine.

24. Device according to claim 23 in which the pistons slide in two supports (31, 32)

5 pierced with orifices (33, 12), these two supports being separated from each other by an annular space, constituting a chamber (35), in which the liners (34) move between two extreme positions, l 'one for which the orifices (36) not being

10 not masked by the jackets (34) all of the liquid discharged by each piston (4) back into the annular chamber (35) through the orifices (36) of the pistons, the flow rate of the pump (I) being zero; the other for which all the orifices (36) being masked by

15 the liners (34) each piston (4) delivers into the volume (13) all of the hydraulic fluid sucked in, the flow rate of the pump (I) then being maximum.

25. Device according to claim 24 in which the shirts (34) can occupy all positions

? 0 intermediaries between the two extreme positions: so that the pump flow (I) can be regulated for all values between a zero flow and a maximum flow.

26. Device according to claim 25, in which all the liners (34) are coupled to a common control member (38) which is controlled by any suitable control device to regulate the flow of gasoline at high pressure as required. to supply the engine without high pressure gasoline being returned to the tank.

27. Device according to claim 26 in which a damping device is arranged downstream of the outlet (29) of the second pump (II) and upstream of the injectors to cancel the pulsation effect caused

'5 by the first pump (I).

28. Device according to claim 27 wherein the damping device is a large volume capacity with respect to the fuel flow rate, maintained under the injection pressure by any suitable means, in the manner of a hydraulic accumulator.