EP1048849A1 - High pressure liquid pump - Google Patents

Abstract

The pump assembly combines a hydraulic pump (I) and a membrane pump (II) in which supple membranes are reciprocated by the displacement of a pumped hydraulic fluid. The pistons (4) of the first pump are hollow and traversed by the hydraulic fluid whic passes in the suction phase through a curved recess in a swashplate (1) or cam. The membrane (24) of the second pump is held in place by a spring (15). At the end of each piston's compression stroke ther a communication between the chamber (12,13) containing the fluid forced against the membrane and the suction chamber (9). The hydraulic fluid is drawn by the movement of the pistons and compressed by the membrane, which ensures a heat exchange between he and non-heated fluids and a return of the membrane to its initial position.

Description

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

Low pressure pumps for this kind of liquids are known, they are of a generally centrifugal, gear, sometimes piston or others, but with known pumps it is impossible, if not very difficult and expensive, to obtain a high discharge pressure (greater than 50 bars), because that as soon as we approach high pressures, seizures of moving parts and large leaks, due to the often very low viscosity pumped fluids.

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

It is also known, for pumping particular liquids such as for example that corrosive liquids, to combine two pumps: a first pump which is a hydraulic pump which pumps and sucks in hydraulic fluid which drives reciprocating the moving parts of a second pump, this last suction and pressurizing the liquid to be pumped. These moving elements which provide physical separation between the hydraulic fluid and the fluid to pump, while being moved alternately by the hydraulic fluid, are either deformable membranes or free pistons.

The free pistons have a defect with regard to sealing, a defect which is essential in the case where one must have an absolute seal. If we put place a seal between the free piston and the cylinder in which it moves, it is not not possible to obtain a perfect seal. If we remove the joint: or there is has 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 leaks, too weak as it is, is not admissible and, obviously, any overheating risks 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 moving parts, driven by an alternative pumping movement by the pump hydraulic and ensuring a completely sealed separation between the liquid hydraulic "motor" and the liquid to be pumped are deformable membranes.

a - si la membrane de séparation et de pompage est mécaniquement liée au piston de la pompe hydraulique, il n'y a pas équipression de chaque côté de la membrane souple et cette dernière ne tient pas dans le temps, elle se détériore ;

b - si la membrane est complètement libre, c'est-à-dire n'est liée à aucun mécanisme d'entraínement et est mue uniquement par le liquide hydraulique refoulé par la pompe, il y a équipression entre les deux côtés de la membrane. Cependant, du fait des inévitables fuites, même très minimes, le volume de liquide hydraulique refoulé augmente à chaque cycle et finit par devenir plus important que celui que peut refouler la membrane : il se produit alors un blocage hydraulique créant une surpression telle que l'une ou l'autre des deux pompes se brise. Dans le cas particulier de l'injection d'essence à haute pression, si c'est l'élément qui refoule l'essence à haute pression qui se brise, l'incendie est inévitable :

c - dans un cas comme dans l'autre, c'est-à-dire que la membrane soit liée au piston ou bien libre, si le volume de liquide hydraulique qui est continuellement refoulé et réaspiré est toujours le même, il va s'échauffer du fait des cycles de compressions indéfiniment répétés, jusqu'à atteindre une température telle que la, ou les, membranes seront détruites.

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 membrane is completely free, that is to say 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 sides of the membrane . However, due to the inevitable leaks, even very small, the volume of hydraulic fluid pumped increases with each cycle and eventually becomes greater 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 high pressure gasoline injection, if it is the element which delivers the high pressure gasoline which breaks, 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 fluid 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 patent 4,392,787 NOTTA, an assembly has been described comprising a hydraulic pump with bias plate, each piston of the pump being associated with its end with a flexible membrane which is connected to a sliding rod inside the piston. This device has the faults described above in "a" and "c". Volume of continuously pressurized liquid is always the same and therefore goes heat. On the other hand, the inevitable small leaks are compensated by admission oil in addition by a non-return valve, but if accidentally a leak important 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 volume hydraulic operated by a piston actuated by a cam. This device has the faults "b" and "c". If it occurs, for whatever reason a shutdown or even a braking of the power supply, the membrane will not redeploy completely and a corresponding amount of hydraulic fluid is going to be introduced at each cycle and this until breaking (drawback "b"). on the other hand, as it is always the same volume of hydraulic fluid that is compressed, 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 piston of hydraulic pump. The disadvantages are the same as for the patent US 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 a piston, the dead chamber, located downstream of the top dead center of this piston (position maximum compression), in which the liquid is in contact with the diaphragm is placed in communication with the hydraulic fluid reserve: from so that the liquid there is pumped back to this reserve first by the expansion of the liquid, then by the effect of repression by the membrane which is constrained by a spring.

On the one hand, a continuously repeated heat exchange is obtained between the compressed liquid and one that is not and, on the other hand, a repositioning initial of the membrane with each cycle or, in other words, elimination of any increase in the volume of hydraulic fluid, acting on the membrane, increase which is inevitably caused permanently by leaks; because it is not possible to realize a high pressure hydraulic pump with pistons, which does not heat up 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 giving it a pressure of very high discharge, of the type constituted by the association of two pumps: on the one hand, a hydraulic pump; on the other hand, a second pump whose mobile means, carrying out the suction and delivery of the liquid to be pumped, are flexible membranes driven in an alternating movement in a direction more in the other by the displacement of the hydraulic fluid pumped then re-aspirated by the first pump characterized in that the pistons of the first pump are hollow and crossed by the hydraulic fluid which, during the suction phase crosses a lunula or groove dug in the face of the bias or cam plate: the deformable membranes each constrained by a spring so that that at the end of the compression stroke of each piston, communication is established between the chamber where the hydraulic fluid is discharged against the membrane and the suction chamber, this liquid being, on the one hand, sucked up by the movement of the piston and driven back by the membrane under the action of its spring, this which ensures: on the one hand an exchange between the hydraulic fluid heated by the compression and the unheated liquid and, on the other hand, a return to the initial position of the membrane.

a - la deuxième pompe comporte autant de volumes ou alésages que la première pompe comporte d'alésages, chaque alésage de la deuxième pompe communiquant directement avec l'alésage correspondant de la première pompe de sorte que chaque piston de la première pompe refoule et aspire cycliquement le liquide hydraulique dans l'alésage correspondant de la deuxième pompe.

b - chaque alésage de la deuxième pompe est divisé en deux parties par une membrane déformable contretenue par un ressort, la partie communiquant avec l'alésage correspondant de la première pompe et recevant le liquide hydraulique refoulé et réaspiré par celle-ci, l'autre partie, munie de clapets d'aspiration et de refoulement, aspirant et refoulant le produit à pomper.

c - la chambre dans laquelle se débattent les têtes des pistons est reliée à un réservoir de liquide hydraulique.

d - le réservoir de liquide hydraulique est extérieur à la première pompe et communique avec cette dernière par une canalisation débouchant dans la chambre.

e - la pompe selon l'invention est destinée à l'alimentation sous haute pression d'injecteurs de carburant pour moteurs à combustion interne, le liquide hydraulique de la première pompe (I) pouvant être l'huile dudit moteur.

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 to the injection devices.

These means are: either the provision of a tilting platform with variable inclination, or the provision of means in the pistons of the hydraulic pump, having for 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 openings that can be completely or partially obscured by a movable folder, all movable liners being moved together by a control member subject to engine operating conditions.

a - les pistons coulissent dans deux supports percés d'orifices, ces deux supports étant séparés l'un de l'autre par un espace annulaire, constituant une chambre, dans laquelle se déplacent les chemises entre deux positions extrêmes, l'une pour laquelle les orifices n'étant pas masqués par les chemises la totalité du liquide refoulé par chaque piston reflue dans la chambre annulaire par les orifices des pistons le débit de la pompe (I) étant nul : l'autre pour laquelle tous les orifices étant masqués par les chemises chaque piston refoule la totalité du liquide hydraulique aspiré, le débit de la pompe étant alors maximum.

b - les chemises peuvent occuper toutes les positions intermédiaires comprises entre les deux positions extrêmes ; de sorte que le débit de la pompe (I) peut être régulé pour toutes les valeurs comprises entre un débit nul et un débit maximum.

c - les chemises sont attelées à un organe de commande commun lequel est asservi à tout dispositif de commande approprié pour réguler le débit d'essence à haute pression en fonction des besoins en alimentation du moteur sans que de l'essence à haute pression ne soit retournée au réservoir.

d - un dispositif amortisseur peut être disposé en aval de la sortie de la deuxième pompe (II) et en amont des injections pour annuler l'effet de pulsation provoqué par la première pompe (I).

e - le dispositif amortisseur peut être une capacité de volume important par rapport au débit d'essence, maintenu sous la pression d'injection par tout moyen approprié et se comporter sensiblement comme un accumulateur hydromécanique.

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 jackets all the liquid discharged by each piston back into the annular chamber by 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 slaved to any suitable control device for regulating 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 injections 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, maintained under the injection pressure by any appropriate means and behave substantially like a hydromechanical accumulator.

• Figure 1, une vue en coupe longitudinale d'un premier mode de réalisation de l'invention.
• Figure 2, une vue en coupe transversale selon A-A de la figure 1.
• Figure 3, une vue en coupe longitudinale de la pompe double à débit variable, les pièces étant dans la position pour laquelle le débit est maximum.
• Figure 4, une vue de la pompe double de la figure 3, les pièces étant dans la position pour laquelle le débit est nul.
• Figure 5, une vue selon A-A de la face du plateau biais des figures 3 et 4.
• Figure 6, une vue en coupe longitudinale de la pompe de la figure 1 dans laquelle les membranes individuelles ont été remplacées par une membrane unique.
• Fifure 7, une vue en coupe selon A-A de la figure 6.
• Figure 8, une vue en coupe selon B-B de la figure 6.
• Figure 9, une vue de détail à échelle agrandie en coupe longitudinale, d'une variante de réalisation de la pompe selon l'invention dans laquelle les clapets d'aspiration ont été supprimés.
• Figure 10, une vue en coupe longitudinale de la pompe de la figure 6 munie du système d'aspiration par la membrane de la figure 9.
• Figure 11, une vue d'une variante de réalisation dans laquelle la pompe hydraulique est une pompe radiale.

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 AA 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 AA 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.
• Fifure 7, a sectional view along AA of FIG. 6.
• Figure 8, a sectional view along BB of Figure 6.
• Figure 9, a detail view on an enlarged scale in longitudinal section, of an alternative embodiment of the pump according to the invention in which the suction valves have been omitted.
• 10, a view in longitudinal section of the pump of FIG. 6 provided with the suction system by the membrane of FIG. 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 by a movement alternating 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 take support against the oblique face of the plate 1 each by means of a sliding pad 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 heads spherical pistons 4a 4 struggle in a chamber 9. This chamber 9 opens, through a plurality of holes 22, passing through the body 21 of the pump 1, 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 reciprocated 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 pressure delivery, they are pushed back to against the spring 7 by the bias plate 1. During the suction phase, the hydraulic fluid which is in the chamber 9 penetrates inside 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 plaintiff.

When the hydraulic pump I is used in a known manner, each bore 12 in which slides a hollow piston 4 has at its end a non-return valve ; so that all of said pistons 4 cause a flow under pressure (and even under 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 slide the pistons 4 does not include a non-return valve.

A pump I 1 is associated with the pump I immediately downstream of the latter.

Each bore 2 of pump I, in which a piston 4 slides, corresponds, in 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 with its end opposite to the membrane 24 of a suction valve 16 and a valve discharge 17. All the valves 17 flow in a common pipe 18.

Preferably, as shown, each spring 15 is supported 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 face rear of the membrane 24 does not cause any deterioration thereof.

The operation is described below:

When the motor shaft 2 is driven, the pistons 4 discharge the hydraulic fluid in chambers 13. The hydraulic fluid discharged into part 13a of the chamber 13, bears on the front face of the membrane 24 and causes a displacement of the latter, in the direction of arrow f1 (fig. 1). By moving this membrane 24 delivers the liquid contained in part 13b of chamber 13. This backflow 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 course for plot 5 on the lunula 8 the liquid under high pressure which is in the chamber 13a relaxes in direction of room 9; then under the action of the spring 7 of the piston 4 and the spring 15 of the membrane 24 the liquid in the chamber 13a is driven back into bore 12 and from there to chamber 9.

So 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, this which prevents any heating of this liquid, which would otherwise be inevitable. Of more, this direct communication between room 13a and room 9, and this, at each cycle, carries out an initial repositioning of the mobile elements so that the volume of hydraulic fluid discharged into the chamber 13a remains strictly equal to itself, the inevitable leaks from the pump hydraulic being returned to chamber 9. This communication of chambers 9 and 13a therefore eliminates the drawbacks described above in "b" and "c".

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

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

Each membrane 24 is subjected, on its two front and rear faces and this of uniformly distributed over the entire surface of the membrane, at the same pressure: on one side the pressure of the engine hydraulic fluid, on the other the pressure of the pumped liquid. The membrane therefore undergoes no mechanical effort and therefore cannot tear.

The pump according to the present invention is therefore a diaphragm pump in which each membrane is, in the delivery phase, an equipression of each side which allows a discharge pressure equal to the pressure that the first pump I.

The pump according to the present invention can be used, inter alia, to put in pressure liquids having no greasing power. In particular it can be used to supply internal combustion engine injectors (car engines) powered by super-fuel and / or LPG liquid as an alternative fuel for example. The super fuel is sucked in by the valves 16, discharged under high pressure (over 50 bars) by the valves 17 without the fuel ever coming into contact with components metal to slide against each other.

It should be noted that at high pressures we can no longer consider liquids as incompressible. When a piston 4 is at the end of the delivery stroke, the hydraulic fluid pressure is at its maximum. As has been said more top, when the stud 5 is on the beginning of the lunula 8 the liquid, while regulator will push back through the piston 4, the passage 6 of the stud 5 and the lunula 8 in room 9; then it will be pushed back by the action of the spring 15. The compressed liquid is hot while the liquid in the chamber 9 and the reservoir is not; he will so there is at each cycle a small exchange of liquid heated by compression and unheated liquid which will ensure thermal equilibrium of the first pump 1. Preferably, although this is not shown, the casing cylindrical 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, engine oil can advantageously be used as hydraulic fluid itself by having chamber 9 communicate directly with the distribution of engine oil, the temperature of this oil being regulated by the appropriate engine components.

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

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

In the case where the hydraulic stage, pump I, is confronted with a strong liquid viscosity, as in the case of cold use, for example, it is preferable. as is known, to have mechanical means maintaining the heads 4a 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 a return to the initial position of the membranes 24, due to the communication with the chamber 9.

If there was not this initial positioning, permitted by this communication with the hydraulic fluid reserve, it could occur a slight drift with each revolution of the pump.

This drift would quickly cause a volume differential between the bore 12 and part 13a of the corresponding bore 13, which in turn would cause quickly an abutment of the membranes 24 and, immediately, a rupture of the pump (either at pump I or at pump II).

It therefore appears that this reset, or reset to the initial position of movable elements 24 of the second pump II, via the lunula 8 is capital city.

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

When this liquid is gasoline intended to supply an engine, it can be interesting to vary the volume of petrol pumped by the pump Il to adapt it to the engine operating conditions.

Before an engine can run at full speed, it is necessary to determine the displacement of the pump according to the extreme conditions of use of the motor, namely: operation at maximum speed and full load. So this defines a flow maximum of the pump which is permanently supplied; so that apart from these extreme conditions of use, the pump provides excess flow. which is returned to the tank.

But the petrol thus brought back to the tank is found to have been heated by the compression, so that hot fuel is constantly brought back to the tank. As the tank empties, the fuel becomes more and more warmer so that it may appear in the vapor tank of unwanted gasoline whose treatment is made difficult by higher standards in addition to being more severe, particularly with regard to petrol injection engines direct.

It is therefore necessary to adjust the pump flow according to the engine requirements.

The first solution consists in making the first pump 1, in the form of a variable flow pump using a bias plate 1 with variable inclination as this is achieved in certain pumps produced by the applicant.

But such a pump may be too expensive for automotive production in large series; 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 allowing to cancel all or part of 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, we see that each hollow piston 4 is crossed through partly 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 jacket sliding 34. These sliding liners are all connected to a connecting rod control 38 so that it can slide all together between two positions extremes, the first being illustrated in Figure 3, the second being illustrated in figure 4.

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

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

The pusher 7b, against the flange 6 of each piston head is crossed by a pipe 37 which makes the two chambers 9 and 35 communicate with each other.

So when, under the effect of the control rod 38, the liners 34 are in the position shown in FIG. 4, the hydraulic fluid discharged by each piston 4 flows back through the pipes 30 and 36 into the annular chamber 35, and from there by the hole 37 in the chamber 9. It follows that the flow of the hydraulic pump I is zero, therefore the membranes 24 are not driven by any movement and exert no pumping and delivery action 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 shirts 34 are in the position shown in Figure 1, the holes 36 are obscured by said shirts and the hydraulic pump I flow is maximum. 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 shirts 34. position determined by the position of the rod 38 which is slaved to the operation of the engine by any appropriate control device.

As a result, the output flow of the pump It is regulated as a function of the flow fuel that is needed for injection and that excess fuel 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. In effect, if for example, the shirts 34 are in a position such that only 10 % of the maximum flow rate of pump I is delivered in part 13a of volume 13, this means that this pump I does not supply any flow during 90% of the stroke of each piston or that there is flow only on 10% of the stroke of each piston. This has the effect that the flow is a pulsed flow.

This therefore 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 way to a hydraulic accumulator, that is to say constituted by a capacity having a large volume compared to the flow supplied to injectors and kept under constant pressure.

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

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 tank 11a; for the rest, all components are identical to the only exception is the diaphragm of pump II in Figure 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 spring 15 corresponding.

More precisely, the pump of FIG. 6, like that of FIG. 1, comprises a one-piece pump housing 40. in two cylindrical parts 40a, and 40b, the part 40b having an internal diameter greater than that of the part 40a. In the part 40a are arranged the bearings 3, the motor shaft 2, the bias plate 1, the supply chamber 9 and the rear part 4 a of a part 41 in which are drilled the bores 12. The front part 41b of this part is located in the part 40b of upper diameter 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 at the front face of this part 41b, a circular plate 42 is disposed against said part 41b and is immobilized in position relative thereto by a pin 42a. This plate 42 has as many bores 43 that there are bores 12 and chambers 13. Chambers 13 are formed in a part 45 which is screwed to the open end of part 40b of the housing 40. Between the part 45 and the plate 42 is disposed a membrane 44 which has the form of a disc having the same diameter as the plate 42. The membrane 44 is pinched between the plate 42 of the end of the part 45. Each hole 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 bore 12, into hole 43 and will deform the part of the membrane 44 which is located opposite the corresponding chamber 13, deformation which occurs 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 17. When the piston 4 moves back in its bore 12, the part of the membrane 44 which had deformed, entered partially into volume 13, is repelled by the spring 15 and returns to its initial shape by sucking the liquid to be pumped by the valve non-return 16.

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

Referring to Figure 9, which is an enlarged view, we see that: at each chamber 13 is associated with a conduit 50 connected to a chamber 51 where the liquid arrives pump through a pipe 52. The pipe 50 is drilled 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 4 and the part 45, in which the chambers are formed 13 has 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 liquid under pressure arrives through the housing 54 and the pipe 55 in the housing 53 and the diaphragm is applied by hydraulic pressure against the pipe opening 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 repels 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 clears 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 by the pipe 52 at a low pressure, of the order of 1 to 2 bars, given by a 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 release the passage 56.

It is also preferable that at the location of each pipe orifice 50 the membrane 44 is provided with a reinforcement cup 57, with a diameter greater than that of the orifice, intended to prevent the membrane from being 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 rest, in the absence of any pressure, it fills the housing 53 and releases the passage 56.

Thus, the membrane 44 by deforming between a position where it is at the bottom of the housing 53 and a position where it closes the suction duct 50 plays the role a suction check valve.

There are, of course, as many conduits 50, housings 53, conduits 55, housing 54 that there are bores 12 and chambers 13.

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

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

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

Such a radial piston pump is shown in FIG. 11.

This pump has a cam 101, which is an eccentric carried by a shaft motor 102, carried by bearings 103. Each piston is a hollow piston 104 restrained 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. Cam 101 struggles in a chamber 109 communicating with a reservoir hydraulic fluid (not shown). Communication between room 109 and the interior of each hollow piston 104 is established when the stud 105 overlaps the groove 108 hollowed out in the cam 101.

The pump It is identical to that of FIG. 1, the same elements carrying the same references.

The cam 101 corresponds to the bias plate 1; pistons 104 to pistons 4; the studs 105 to studs 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 Figure 10 is identical to that of the pumps previously shown.

Claims (27)

Pump allowing to pump any kind of liquid while it printing a very high discharge pressure, of the type constituted by the combination of two pumps: on the one hand, a hydraulic pump (1); 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 animated by a reciprocating in one direction then in the other by the displacement of the liquid hydraulic pumped then re-aspirated by the first pump (I) characterized by the fact that the pistons (4, 104) of the first pump (I) are hollow and crossed by the hydraulic fluid which, during the suction phase, 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 stroke compression of each piston (4, 104), communication is established between the chamber (12-13) where the hydraulic fluid is forced 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 membrane (24, 44) under the action of its jurisdiction (15) which ensures both: an exchange between the hydraulic fluid heated by compression and unheated liquid; and one return to the initial position of the membrane (24, 44). Pump according to claim 1, wherein the first pump (I) or pump hydraulic is a bias plate pump (1) and axial pistons (4) said pistons axial being hollow and constrained by springs (7, 7a) so that the head (4a) of each hollow piston (4) is in abutment against the bias plate (1) by through 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) and the chamber (13a) in which the hydraulic fluid was driven back during the compression phase. Pump according to claim 1, wherein the first pump (1) or pump hydraulic is a radial piston pump (104) driven by a cam (101); said radial pistons (104) being hollow and constrained by springs (107) of so that the head (104a) of each hollow piston (104) bears against the cam (101) by means of a sliding stud (105) traversed by a bore central (106), this stud overlapping a groove (108) etched on the surface of the cam (101) during the suction phase of the corresponding piston, so that establish during this phase a direct communication between the room (109) where the cam (101) and the chamber (13a) in which the hydraulic fluid struggles was pushed back during the compression phase. Pump according to claim 2, in which the second pump (II) comprises as many chambers or bores (13) as the first pump (1) 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 aspirates cyclically the hydraulic fluid in the corresponding chamber (13) of the second pump (II). The pump of claim 4, wherein each bore (13) of the second pump (II) is divided into two parts (13a, 13b) by a membrane deformable (24) supported by a spring (15), the part (13a) communicating with the corresponding bore (12) of the first pump (I) and receiving the liquid hydraulic pumped back and sucked back by it; the other part (13b), fitted with valves suction (16) and discharge (17), sucking and discharging the product to be pumped. Pump according to claim 5, in which each spring (15) is supported 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). 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) struggle is connected to a hydraulic fluid tank. Pump according to claim 7, in which the liquid reservoir (11) hydraulic is external to the first pump (I) and communicates with this the latter by a pipe (10) opening into the chamber (9). Pump according to claim 7, in which the reservoir (11) consists of a cylindrical casing (23) surrounding the body (21) of the first pump and communicating with the chamber (9) through a plurality of orifices (22). Pump according to claim 2, in which the deformable membranes individual (24) are replaced by a single membrane (44) interposed between the bores (12) of the pistons (4) and the chambers (13). The pump of claim 10, wherein a circular plate (42) is interposed between the part (41) in which the bores (12) are formed and the room (45) in which the chambers (13) are formed, this room making communicate by holes (43) each bore (12) with the chamber (13) which corresponds to him. Pump according to claim 10, wherein in each chamber (13) is disposed a spring (15) which bears on the membrane (44) by means of a cup (20). Pump according to claim 12, in which each chamber (13) is associated with a suction non-return valve (16) and a non-return valve delivery (17). Pump according to claim 12, in which each chamber (13) is not associated with a discharge non-return valve (17), the non-return valve (16) being removed and its function fulfilled by the membrane (44) herself. Pump according to claim 14, in which the inlet duct (50) of the liquid to be pumped opens against the membrane (44) which is held in abutment against the orifice of this conduit during the delivery phase and is removed therefrom during the aspiration phase. The pump of claim 15, wherein the portion of the diaphragm (44) which bears against the orifice (50) for the arrival of the liquid is provided with a cup reinforcement (57). Pump according to claim 15, in which during the suction phase, the membrane (44) comes to the bottom of a housing (53) in order to clear a passage (56) of communication between the liquid inlet pipe (50) and the chamber (13). The pump of claim 17, wherein the diaphragm (44) is preformed molding to occupy the bottom of the housing (53) during suction to clear the passage (56). Pump according to any one of the preceding claims, characterized by the fact that it is intended for the high pressure supply of injectors of fuel for internal combustion engines, the hydraulic fluid of the first pump (I) possibly being the oil of said motor. Pump according to claim 19, characterized in that it comprises means for varying the flow rate of the hydraulic pump (I) and, by means of consequence, the pump flow (II) so as to adapt the pumped petrol flow at high pressure to the injectors at engine operating conditions. Pump according to claim 20, in which the bias plate of the pump hydraulic (I) is a variable tilt platform. Pump according to claim 20, characterized in that each piston (4) of the hydraulic pump (I) is provided with openings (36) which can be concealed, while or in part, by a movable shirt (34), all the movable shirts (34) being moved together by a control member (38) subject to the conditions of engine operation. Device according to claim 22, in which the pistons slide in two supports (31, 32) pierced with orifices (33, 12), these two supports being separated one from the other by an annular space, constituting a chamber (35), in which the shirts (34) move between two extreme positions, one for which the orifices (36) not being masked by the liners (34) all of the liquid discharged by each piston (4) back into the annular chamber (35) through the orifices (36) pistons, the flow rate of the pump (1) being zero: the other for which all orifices (36) being masked by the liners (34) each piston (4) pushes back into the volume (13) all of the hydraulic fluid drawn in, the flow rate of the pump (I) being then maximum. Device according to claim 23, in which the shirts (34) can occupy all the intermediate positions between the two positions extremes: so that the pump flow (I) can be regulated for all values between zero flow and maximum flow. Device according to claim 24, in which all the shirts (34) are coupled to a common control member (38) which is controlled by any device control unit suitable for regulating fuel flow at high pressure in according to the power requirements of the engine without high gasoline pressure is returned to the tank. Arrangement according to claim 25, in which a damping device is disposed downstream of the outlet (29) of the second pump (II) and upstream of the injectors to cancel the pulsation effect caused by the first pump (I). Device according to claim 26, in which the damping device is a large volume capacity compared to the fuel flow, maintained under the injection pressure by any suitable means, like an accumulator hydraulic.

Images