EP1876353A1 - Transfer pump with several pistons - Google Patents

Abstract

The pump has bellows (4a, 4b) alternately filled with and emptied of hydraulic liquid at high pressure by pistons (1a, 1b) driven by respective cams (2a, 2b). The cams are angularly offset by 60 degrees and carried by a camshaft (3). Chambers (5a, 5b) are supplied with fuel, whose quantity is determined by a flow-monitoring solenoid valve (8) controlled by a computer. The bellows move in the chambers. The piston and the bellows are supplied by a single supply circuit (6), on which the solenoid valve is placed. The system has a conveyor duct (10) that is common to the pistons and the bellows.

Description

The subject of the present invention is a pump of the type known as a transfer pump, that is to say of the type comprising a mobile element pumping an aggressive liquid of the automotive fuel type, this mobile element being reciprocated by means of oil pumped by a hydraulic pump.

It is known to use a single-piston hydraulic pump, said single-piston pump, for supplying high pressure fuel to the injectors of an engine.

A pump of this kind is described in the patent US 1,696,825 of December 25, 1928 ; as well as in the patent application 06/02594 of 24 March 2006 , on behalf of the applicant.

However, it turns out that for high displacements, the flow rate provided by a single piston pump is insufficient.

Indeed, it turns out that there is, in practice, a maximum limit of the displacement of single-piston pumps, which limit is about a little more than 1c.c. per turn.

To increase this displacement it would be necessary either to increase the stroke of the piston, or to increase the diameter. If we increase the race, the acceleration is considerable; if we increase the diameter, it is the force in contact with the cam driving the piston becomes too important.

It has therefore been proposed to have two single-screw pumps, but it is necessary to double the electronic control means, which is suitable for a prototype but is not suitable, economically, for production very large series (for 1,000 engines per day, it requires 2,000 single-screw pumps with 2,000 electronic control devices).

These electronic control means are, in general, solenoid valves controlled by the engine control computer.

The transfer pump according to the invention is of the type in which the mobile pumping element is a metal bellows alternately filled and emptied of hydraulic fluid at high pressure, the quantity of fuel admitted into the chamber in which said bellows moves being determined, upstream, by a solenoid valve controlled by the engine control computer, characterized in that it comprises at least two pump assemblies (bellows / piston) which are fed by a single intake circuit, common to both sets .

1. a. le circuit de refoulement est commun aux ensembles de pompage ;
2. b. la pompe comporte deux pistons, chaque piston étant actionné par une came, les deux cames étant portées parallèlement par un arbre à cames et étant angulairement décalées de 60° ;
3. c. la pompe comporte "n" pistons, chaque piston étant actionné par une came, les "n" cames étant portées parallèlement les unes aux autres par un arbre à cames et étant angulairement décalées ;
4. d. la pompe comporte une seule came et au moins deux pistons disposés radialement autour de la came ;
5. e. la pompe comporte deux pistons qui sont disposés en V à 60° l'un de l'autre.

The present invention may, in addition, comprise all or part of the following provisions:

1. at. the discharge circuit is common to the pumping sets;
2. b. the pump comprises two pistons, each piston being actuated by a cam, the two cams being carried parallel by a camshaft and being angularly offset by 60 °;
3. vs. the pump comprises "n" pistons, each piston being actuated by a cam, the "n" cams being carried parallel to each other by a camshaft and being angularly offset;
4. d. the pump comprises a single cam and at least two pistons arranged radially around the cam;
5. e. the pump comprises two pistons which are arranged in a V at 60 ° to each other.

• Figure 1, une vue schématique d'un premier exemple de réalisation de l'invention.
• Figure 2, une variante de la figure 1.
• Figure 3, une vue en perspective illustrant une pompe selon la figure 1.
• Figure 4, une vue schématique d'une variante de réalisation des figures 1 et 2 avec "n" pistons.
• Figure 5, une vue schématique d'un deuxième exemple de réalisation de l'invention.

As non-limiting examples and to facilitate the understanding of the invention, there is shown in the accompanying drawings.

• Figure 1 is a schematic view of a first embodiment of the invention.
• Figure 2, a variant of Figure 1.
• 3 is a perspective view illustrating a pump according to FIG.
• Figure 4 is a schematic view of an alternative embodiment of Figures 1 and 2 with "n" pistons.
• Figure 5 is a schematic view of a second embodiment of the invention.

With reference to FIGS. 1 and 2, it can be seen that the pump according to the invention comprises two pistons 1a and 1b driven by two parallel cams 2a and 2b and carried by a shaft 3.

Each cam 2a and 2b has three lobes, arranged at 120 ° from each other (as shown in Figure 3).

In a manner known per se, each piston 1a and 1b displaces hydraulic fluid within a bellows 4a, 4b which elongates and retracts into a chamber 5a, 5b. The interior of the bellows 4a, 4b receives hydraulic fluid which is put in high pressure when the piston 1 rises, high pressure which is communicated to the fuel in the chambers 5a, 5b.

According to the present invention, the fuel is admitted into the two chambers 5a, 5b by means of a single feed circuit 6 which has two branches 6a, 6b.

The supply circuit 6 is connected by the orifice 7 to the tank through a solenoid valve 8 which measures the amount of fuel that can be introduced into the chambers 5a and 5b.

Two nonreturn valves 7a, 7b allow the fuel supplied by the pipe 6 to enter the chambers 5a, 5b and two check valves 9a, 9b allow the fuel discharged at high pressure by the bellows 4a, 4b to flow. in the single discharge pipe 10 to the discharge port 11.

Preferably, the cams 2a and 2b are angularly offset by 60 °.

• comme il y a un circuit unique d'alimentation et de refoulement, il y a moins de composants qu'avec 2 pompes monopiston standard.
• en particulier, il n'y a qu'une seule électrovanne 8 pour contrôler la quantité de carburant envoyée au moteur.
• l'effort exercé par les pistons sur l'arbre à cames 3 est moindre à cylindrée équivalente que s'il n'y avait qu'un seul piston.
• le décalage angulaire des deux cames 2 a pour effet une meilleure progressivité de l'écoulement sous pression vers le rail d'injection et permet de réduire les variations du couple sur l'arbre à cames.

This provision brings the following advantages:

• As there is a single supply and discharge circuit, there are fewer components than with 2 standard single piston pumps.
• in particular, there is only one solenoid valve 8 to control the amount of fuel sent to the engine.
• the force exerted by the pistons on the camshaft 3 is smaller at equivalent displacement than if there was only one piston.
• the angular offset of the two cams 2 has the effect of a better progressivity of the flow under pressure towards the injection rail and makes it possible to reduce the variations of the torque on the camshaft.

In the embodiment shown in Figure 1, the discharge circuit is common to both pistons 1a and 1b; but the invention is not limited to this particular embodiment: it can have a discharge circuit 10a and 10b for each piston as shown in Figure 2 wherein the same elements have the same references.

FIG. 4 illustrates an alternative embodiment in which the same elements bear the same references.

According to this variant, there are more than two pistons 1a, 1b ... 1 n each driven by a cam 2a, 2b ... 2n, these cams being parallel to each other and carried by the same camshaft 3.

There is a discharge circuit 10 common to all "n" pistons, as in the case of Figure 1; but it would be possible to have a discharge circuit (10a, 10b ... 10n) for each piston, as in the case of Figure 2.

The only difference with the pump of Figure 1 is that there is only one cam 1 (the camshaft 3 being symbolically figured) to animate the two pistons 1a and 1b, but that those they are placed in V, their axes being arranged at 60 °.

The same advantages are obtained as in the example of FIG. 2, the assembly being a little more compact.

In this same FIG. 5, an additional piston 1 m is symbolically represented by the connection 6 m of the pipe 6 and being connected in 10 m to the discharge pipe 10.

This representation is intended to demonstrate that it is possible to have, radially, a plurality "m" of pistons, around the cam 2.

In all the examples shown, the cams are cams with three lobes arranged at 120 ° from each other; but it should be noted that the invention is not limited to this particular example: the cam 2 may comprise one or more lobes.

Claims (7)

Transfer pump of the type in which the mobile pumping element is a bellows (4) alternately filled and emptied of hydraulic fluid put under high pressure by a piston (1) driven by a cam (2), the quantity of fuel admitted into the chamber (5) in which the bellows (4) is determined, upstream, by a solenoid valve (8) controlled by the engine control computer, characterized in that it comprises at least two pump assemblies ( piston 1 / bellows 4) which are fed by a single intake circuit (6) common to the assemblies on which the flow control solenoid valve (8) is placed and which have a discharge circuit (10) which may be unique and common, or specific to each pumping unit. Pump according to claim 1, wherein the pistons (1) are actuated by at least one cam (2) single-lobe or multi-lobes. Pump according to claim 2, comprising a plurality of pistons (1a, 1b ... 1n) animating bellows (4a, 4b ... 4n) arranged in chambers (5a, 5b ... 5n) connected to a supply circuit common (6). Pump according to claim 3, wherein the chambers (5a, 5b ... 5n) are connected to a common discharge circuit (10). Pump according to claims 1 to 4, wherein the pistons (1a, 1b ... 1 n) are actuated by cams (2a, 2b ... 2n) mono-lobe or multi-lobes, arranged byrelement on a shaft to cams (3). Pump according to claim 3, wherein the chambers (5a, 5b ... 5n) are each connected to a discharge circuit of its own. Pump according to claims 1 to 4, wherein the pistons (1a, 1b ... 1 n) are actuated by a single cam (2), said pistons being arranged radially around the cam (2).

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