Transfer pump with several pistons

Abstract

Transfer pump of the type in which the moving part for pumping is a bellows (4) that is alternately filled with and emptied of hydraulic liquid at high pressure by a piston (1) that is driven by a cam (2), whereby the amount of fuel allowed into the chamber (5) into which the bellows (4) moves is determined, upstream, by a solenoid valve (8) that is driven by the computer for monitoring the engine, characterized by the fact that it comprises at least two pumping units (piston 1/bellows 4) that are supplied by a single intake system (6) that is common to the units on which the flow-monitoring solenoid valve (8) is placed and that have a conveyor circuit (10) that may be unique and common, or specific to each pumping unit.

Description

By way of nonlimiting examples and to facilitate the understanding of the invention, there have been shown in the accompanying drawings:

FIG. 1, a diagrammatic view of a first embodiment of the invention.

FIG. 2, a variant of FIG. 1.

FIG. 3, a perspective view illustrating a pump according to FIG. 1.

FIG. 4, a diagrammatic view of a variant embodiment of FIGS. 1 and 2 with “n” pistons.

FIG. 5, a diagrammatic view of a second embodiment of the invention.

By referring to FIGS. 1 and 2, it is seen that the pump according to the invention comprises two pistons 1a and 1b that are driven by two cams 2a and 2b that are parallel and carried by a shaft 3.

Each cam 2a and 2b comprises three lobes, placed at 120° C. from one another (as is shown in FIG. 3).

In a way that is known in the art, each piston 1a and 1b moves hydraulic liquid inside a bellows 4a, 4b, which extends and retracts in a chamber 5a, 5b. The inside of the bellows 4a, 4b receives hydraulic liquid that is put under high pressure when the piston 1 rises, high pressure that is communicated to the fuel that is found in the chambers 5a, 5b.

According to this invention, the fuel is allowed into the two chambers 5a, 5b by means of a single supply circuit 6 that comprises two branches 6a, 6b.

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

Two nonreturn valves 7a, 7b allow the fuel that is fed via the hose 6 to penetrate the chambers 5a, 5b, and two nonreturn valves 9a, 9b allow the fuel that is fed at high pressure via the bellows 4a, 4b to flow into the single conveyor duct 10 toward the conveyor orifice 11.

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

This arrangement provides the following advantages:

• • As there is a single supply and conveyor circuit, there are fewer components than with two standard single-piston pumps.
  • In particular, there is only a single solenoid valve 8 for monitoring the amount of fuel sent to the engine.
  • The force exerted by the pistons on the camshaft 3 is less than the equivalent capacity that would be present if there were a single piston.
  • The angular offset of the two cams 2 ensures better progressiveness of the pressurized flow toward the injection rail and makes it possible to reduce the variations of the torque on the camshaft.

In the embodiment shown in FIG. 1, the conveyor circuit is common to two pistons 1a and 1b, but the invention is not limited to this particular embodiment: it is possible to use a conveyor circuit 10a and 10b for each piston as is illustrated in FIG. 2 in which the same elements bear the same references.

FIG. 4 illustrates a variant embodiment in which the same elements bear the same references.

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

There is a conveyor circuit 10 that is common to all “n” pistons, as in the case of FIG. 1; but it would be possible to use a conveyor circuit (10a, 10b . . . 10n) for each piston, as in the case of FIG. 2.

The only difference with the pump of FIG. 1 is that there is only a single cam 1 (whereby the camshaft 3 is drawn symbolically) to drive the two pistons 1a and 1b, but the latter are placed in a V, their axes being arranged at 60°.

The same advantages as in the example of FIG. 2 are obtained, whereby the unit is a bit more compact.

In this same FIG. 5, an additional piston 1m, . . . is shown symbolically by the branching 6m of the duct 6 and by being connected at 10m to the conveyor duct 10.

The purpose of this representation is to demonstrate that it is possible to use, in a radial manner, a number “m” of pistons, around the cam 2.

In all of the examples that are shown, the cams are cams with three lobes arranged at 120° from one another, but it is necessary to note that the invention is not limited to this particular example: the cam 2 can comprise one or more lobes.

Claims

1. Transfer pump of the type in which the moving part for pumping is a bellows (4) that is alternately filled with and emptied of hydraulic liquid at high pressure by a piston (1) that is driven by a cam (2), whereby the amount of fuel allowed into the chamber (5) into which the bellows (4) moves is determined, upstream, by a solenoid valve (8) that is driven by the computer for monitoring the engine, characterized by the fact that it comprises at least two pumping units (piston 1/bellows 4) that are supplied by a single intake system (6) that is common to the units on which the flow-monitoring solenoid valve (8) is placed and that has a conveyor circuit (10) that may be unique and common, or specific to each pumping unit.

2. Pump according to claim 1, wherein the pistons (1) are actuated by at least one single-lobe or multi-lobe cam (2).

3. Pump according to claim 2, comprising several pistons (1a, 1b . . . 1n) that drive bellows (4a, 4b . . . 4n) that are arranged in chambers (5a, 5b . . . 5n) that are connected to a common supply circuit (6).

4. Pump according to claim 3, wherein the chambers (5a, 5b . . . 5n) are connected to a common conveyor circuit (10).

5. Pump according to claim 1, wherein the pistons (1a, 1b . . . 1n) are actuated by single-lobe or multi-lobe cams (2a, 2b . . . 2n) that are arranged in parallel on a camshaft (3).

6. Pump according to claim 3, wherein the chambers (5a, 5b . . . 5n) are each connected to a conveyor circuit that is specific thereto.

7. Pump according to claim 1, wherein the pistons (1a, 1b . . . 1n) are actuated by a single cam (2), whereby said pistons are arranged radially around the cam (2).

8. Pump according to claim 2, wherein the pistons (1a, 1b . . . 1n) are actuated by single-lobe or multi-lobe cams (2a, 2b . . . 2n) that are arranged in parallel on a camshaft (3).

9. Pump according to claim 3, wherein the pistons (1a, 1b . . . 1n) are actuated by single-lobe or multi-lobe cams (2a, 2b . . . 2n) that are arranged in parallel on a camshaft (3).

10. Pump according to claim 4, wherein the pistons (1a, 1b . . . 1n) are actuated by single-lobe or multi-lobe cams (2a, 2b . . . 2n) that are arranged in parallel on a camshaft (3).

11. Pump according to claim 2, wherein the pistons (1a, 1b . . . 1n) are actuated by a single cam (2), whereby said pistons are arranged radially around the cam (2).

12. Pump according to claim 3, wherein the pistons (1a, 1b . . . 1n) are actuated by a single cam (2), whereby said pistons are arranged radially around the cam (2).

13. Pump according to claim 4, wherein the pistons (1a, 1b . . . 1n) are actuated by a single cam (2), whereby said pistons are arranged radially around the cam (2).