US3871794A

US3871794A - Correction device for the delivery per revolution of a distributing injection pump and pump equipped with this device

Info

Publication number: US3871794A
Application number: US369179A
Authority: US
Inventors: Jean Leblanc
Original assignee: Sigma
Current assignee: Sigma; Industrielle Generale de Mecanique Appliquee SIGMA SA
Priority date: 1972-06-19
Filing date: 1973-06-12
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18
Also published as: DE2331027A1; GB1435014A; DE2331027B2; DE2331027C3; FR2190163A5

Abstract

The pump comprises a fixed body and a rotary distributor driven, inside said body, by a substantially coaxial shaft, itself driven by the engine supplied by the pump. The rotary distributor comprises distributing passages, inclined to its longitudinal direction and adapted to cooperate with the pumping and delivery means so that a longitudinal displacement of the distributor causes the delivery per revolution of the pump to vary. A regulator sensitive to the rotary speed of the drive shaft is provided to control the longitudinal displacements of the distributor, the latter being subject, on the one hand, to the action of the regulator, through thrust means and on the other hand, to the contrary action of elastic return means through a transmission lever mounted on pivoting means borne by a casing shielding the pump. The pivoting means is arranged so that its geometrical axis of rotation is displaceable to cause longitudinal movement of the distributor. It comprises control means for this displacement, sensitive to the pressure of a fluid.

Description

United States Patent [1 1 1111 3,871,794 Leblanc 1 1 Mar. 18, 1975 [54] CORRECTION DEVICE FOR THE 3,330,265 7/1967 Giraudon et a1. 123/140 R E R PER REVOLUTION OF A 3,635,603 1/1972 Eheim 417/294 X DISTRIBUTING INJECTION PUMP AND PUMP EQUIPPED WITH THIS DEVICE Primary Examiner-C. .l. Husar Assistant Examiner-Richard Gluck [75] lnvemor? Jean Leblanc Lyon! Frame Attorney, Agent, or Firm-Larson, Taylor & Hinds [73] Assignee: Societe Industrielle Generale De Mecanique Appliquee S.l.G.M.A., [57] ABSTRACT Vemssmulb France The pump comprises a fixed body and a rotary distrib- [22] Filed: June 12 1973 utor driven, inside said body, by a substantially coaxial shaft, itself driven by the engine supplied by the pump. PP N05 3691179 The rotary distributor comprises distributing passages, inclined to its longitudinal direction and adapted to [30] Foreign Application Priority Dam cooperate w th the pumping and delivery means so J n 9 972 F n e 72 22041 that a longitudinal displacement of the distributor u e m c causes the delivery per revolution of the pump to vary. A regulator sensitive to the rotary speed of the drive [52] 417/282 417/294 shaft is provided to control the longitudinal displace- 151] [m Cl F04 49/00 F02d 1/04 ments of the distributor, the latter being subject, on [58] Fie'ld R MO 139 Ah the one hand, to the action of the regulator, through 4l7l282 thrust means and on the other hand, to the contrary action of elastic return means through a transmission lever mounted on pivoting means borne by a casing {561 References cued shielding the pump. The pivoting means is arranged so UNITED STATES PATENTS that its geometrical axis of rotation is displaceable to 2.306.733 12/1942 19 123/139 AW cause longitudinal movement of the distributor. 1t g a comprises control means for this displacement, sensi- 1., 511' S 1 t f f. 3.077.117; 2/1963 Parks ct =11. 123/140 MC m he pressure 0 a 3,323,506 6/1967 Pigeroulet et a1. 123/139 AL 6 Claims, 4 Drawing Figures :fiezfisa J E 65 wag g a? 33 Jim? s 498 F a? 40 l 59 Q2 46 I 66 u 1 1 G %b 53,5 g9 45 U 1 E 151a 16 jzzd PATENTEDMARI ms 87 l 794 sum 2 or 4 CORRECTION DEVICE FOR THE DELIVERY PER REVOLUTION OF A DISTRIBUTING INJECTION PUMP AND PUMP EQUIPPED WITH THIS DEVICE The invention relates to a correction device for the flow-rate per revolution of a distributing rotary injection pump, for an internal combustion engine, which pump comprises a fixed body and a rotary distributor driven, inside said body, by a substantially coaxial shaft, itself driven by the engine supplied by the pump, the rotary distributor comprising distributing passages, inclined to its longitudinal direction and adapted to cooperate with pumping and delivery means so that a longitudinal displacement of the distributor causes the flow-rate per revolution of the pump to vary, a regulator sensitive to the rotary speed of the drive shaft being provided to control the longitudinal displacements of the distributor, the latter being subject, on one hand, to the action of the regulator, through thrust means and, on the other hand, to the opposite action of elastic return means by means of a transmission lever mounted on pivoting means borne by a casing shielding the pump.

The invention relates more particularly, because it is in this case that its application seems to have the most advantage, but not exclusively, to a correction device for the flow-rate per revolution of a distributing injection pump for a supercharged internal combustion engine, that is to say of which the combustion air is supplied by a turbo-compressor or a similar device, driven by the engine.

It is a particular object of the invention to render the correction device such that it responds to the various exigencies of practice better than hitherto, and especially so that it permits a correction of the flow-rate per revolution to be effected in response to the pressure of a fluid, in particular to the pressure of the supercharging air.

According to the invention, a correction device for the flow-rate per revolution, as previously defined is characterised by the fact that pivoting means of the transmission lever on the casing are arranged so as to enable displacement of the geometrical axis of rotation of said lever driving a longitudinal movement of the distributor, and that it comprises control means for this displacement of the geometrical axis of rotation of the transmission lever, sensitive to the pressure of a fluid.

Advantageously, pivoting means of the transmission lever comprise a pivot borne by the casing, on which pivot is mounted in eccentric manner, the pivoting axle of said lever.

Preferably, control means of the displacements of the geometrical axis of rotation of the transmission lever are constituted by a jack.

A fork may be provided, of which the plane is perpendicular to the axis of the pivot, keyed in rotation on said pivot and adapted to cooperate with a rotary link rod of which the rotation is controlled by the rod of the jack.

In the case of a supercharged engine, the control means for the displacements of the geometrical axis of pivoting of the transmission lever are sensitive to the pressure of the supercharging air and are arranged so that a reduction in the pressure of this supercharging air causes a reduction in the delivery per revolution of the pump and conversely in the case of an increase.

Preferably, the axis of the jack is parallel to that of the distributor.

The invention consists, apart from the features mentioned above, of certain other features which will be more explicitly considered below, with regard to a preferred embodiment of the invention which will now be described, in more detailed manner, with reference to the accompanying drawings, but .which is in no way to be considered as limiting.

FIG. 1 of these drawings shows, in partial axial section, a distributing rotary injection pump, equipped with a correction device according to the invention.

FIG. 2 is a section along the line Illl (FIG. 1) of the correction device with portions removed.

FIG. 3 is a view from the left with respect to FIG. 1.

FIG. 4, lastly, shows the. variations in flow-rate per revolution (0) borne as ordinates as a function of the rotary speed of the engine (N).

Referring to FIG. 1, it can be seen that the distributing injection pump, as a whole, is arranged in a conven tional way, for example that described in U.S. Pat. No. 3,323,506 filed 15 Dec. I964 by Jean PIGEROULET and Raymond TISSOT and assigned to Societe Industrielle Generale de Mecanique Appliquess S.I.G.M.A. The description of this pump will only be included very succinctly since it suffices to refer to the abovesaid patent for a detailed description.

The pump comprises a fixed body 1, preferably in two coaxial parts 10 and lb and a rotary distributor or slide valve 2 driven in rotation, inside of a bore 3 formed in the body, by a coaxial shaft 4, which is itself driven by the engine (not shown) supplied by the pump.

The slide valve 2 comprises distributing passages d, inclined to its longitudinal direction and constituted by longitudinal helical grooves.

These passages d are adapted to cooperate with pumping and delivery means 5 for supplying fuel under pressure to the injectors of the internal combustion en gine.

The description of these pumping and delivery means 5, which are conventional, is not taken up. For such additional description it suffices to refer to the abovementioned patent.

The pumping means 5 are supplied by a primary pump 6, for example with conjugated inner profiles, also conventional.

The assembly is arranged so that a longitudinal displacement of the distributor 2, as a consequence of the cooperation of the abovesaid inclined passages d with the pumping and delivery means 5, causes the flow-rate per revolution of the injection pump to vary.

A centrifugal regulator 7, sensitive to the rotary speed of the drive shaft 4, is provided to control the longitudinal displacements of the slide valve 2.

The regulator 7 is of the type with centrifugal weights 8 each pivoted on an axle 9 and adapted to control, by fingers (not shown) cooperating with a groove 10 of a bush 11, the longitudinal displacements of this bush.

The slide valve 2 is subject to the action of the centrifugal weights 8, through thrust means p comprising, in addition to the bush 11, a ring (or cross-member) 12, arranged between the bush 11 and the slide valve 2 and connected in rotation to the shaft 4. The bush II and the ring 12 are mounted in a blind bore of the shaft 4, coaxial with the slide valve 2, one end 2b of this slide valve entering said blind bore. A helical spring 13 is provided between the ring 12 and the slide valve 2.

A pin 14, perpendicular to the axis of the shaft 4, is mounted inside the ring 12, the ends of the pin 14 being located in holes provided in said ring. This pin 14 is connected in translation and in rotation to the ring l2. At least, the end 2b of the slide valve 2 is hollow and comprises two diametrically opposite longitudinal grooves 15, preferably in a helix, and closed at their longitudinal ends. These grooves 15 are traversed by a pin 14.

A pushrod 16, such as that described in the abovementioned patent is advantageously provided. This cylindrical pushrod passes through a longitudinal cavity provided then in the entire slide valve 2 and, at its end neighboring the ring 12, is traversed by the pin 14.

At its longitudinal end distant from the bush, the pushrod 16 is equipped with a ferrule 17 terminated by a frustoconic part 18, whose generators converge in the direction which recedes from the slide valve 2.

A cup 19 is mounted free in translation in a sleeve 20 mounted free in rotation, on that of the ends of the slide valve 2 which is distant from the ring 12, by means of a ball bearing 21.

As described in the above-mentioned patent, the cup 19 comprises, on the side of the slide valve 2, a frustoconic surface 19a inclined to the axial direction of the slide valve 2.

Balls 22 are arranged between the cup l9 and the ferrule l7, so as to be supported against the frustoconic surfaces 18 and 19a and the front end 2d of the slide valve 2.

The slide valve 2 is subject to the action of elastic return means R through a lever 23 mounted on pivoting means 24 which are borne by a casing E shielding the injection pump and the correction device. The end 23b of the lever 23 is supported against the cup 19. The elastic return means R comprise an assembly of three coaxial

helical springs

25, 26 and 27 of which the axis is parallel to that of the slide valve 2. At one end, these springs are supported against a cup 28 adapted to slide on a rod 29 parallel to said slide valve.

The

springs

27 and 26, constituting respectively the slow speed spring and the high speed" spring, are supported at their other end against a cup 30, adapted also to slide on the rod 29. This cup is stopped by a shoulder 29a of said rod. A sleeve 31 is screwed on the cup 30 on the side of the latter which is opposite the

springs

26 and 27. This sleeve 31 has an inner shoulder serving as an axial stop for a cap 32 which possesses a collar 32a projecting externally. A spring 33 coaxial with the rod 29 is compressed between this cap 32 and a washer 34 supported against the cup 30, said washer 34 comprising a part 340 in the form of a cylindrical sleeve adapted to be engaged inside the spring 33 to serve as a guide for it. At rest, the spring 33 holds the cap 32 spaced from the cup 30 with a play j.

The spring 25 or overload spring is supported, at its end distant from the cup 28, against a bush 35, adapted to slide on the sleeve 31. This bush is fast to a transverse bottom 36, supported against the end 23a of the lever 23 which is opposite the end 23b. This bottom 36 is provided to come into abutment against the cap 32, but it can be separated therefrom by the spring 25.

The tension of the

springs

25, 26 and 27 is adjusted at will by a rotary cam 37 connected to the accelerator control and adapted to displace the cup 28 along the rod 29. The latter is screwed on the casing B in adjustable manner in the longitudinal direction.

The pivoting means 24 of the lever 23 are situated in the middle part of said lever and are arranged so as to enable a displacement of the geometrical axis of rotation A of this lever which drives a longitudinal movement of the slide valve 2.

As seen in FIG. 2, the pivoting means 24 comprise a pivot 38 whose axis is perpendicular to the plane passing through the axes of the slide valve 2 and of the rod 29. This pivot 38 is borne by the casing E by means of a yoke 39 with a U section, as seen in FIG. 2. This yoke comprises 2 flanges perpendicular to the axis of the pivot 38 and connected by a part supported against the casing E and fixed to the latter by a screw 40. The pivot 38 comprises a part 380 (FIG. 2) of large diameter, pivoted in one of the flanges of the yoke 39, and a part 38b of smaller diameter and pivoted in the other flange of the yoke 39.

The material pivoting axle 41 of the lever 23 is mounted in eccentric manner on the pivot 38 and is constituted, preferably, by a cylindrical portion fast to the parts 38a, 38b and situated between the two flanges of the yoke 39. The eccentricity between the geometric axis A of the part 41 and the geometric axis of the pivot 38 is denoted by e in FIG. 2 where the said pivot 38 has turned by with respect to its position in FIG. 1 in order to make the eccentricity appear more clearly. However, at rest, as shown in FIG. 1, the geometric axes of the pivot 38 and of the axis 41 are situated in a same plane perpendicular to the axis ofthe slide valve 2. The diameter of the part 38b is less than that of the axle 41, whilst the diameter of the part 380 is greater than that of the axle 41. The transverse blocking of the part formed by the pivot 38 and the axle 41 in the yoke 39 is ensured by the cooperation of the shoulder formed at the junction of the axle 41 and of the part 38b with the inner surface neighboring the flange adjacent the yoke 39 and by the cooperation of an elastic stop ring 42 anchored on the end 38b and adapted to cooperate with a washer supported against the outer surface of said flange of the yoke 39.

A bearing 43 is arranged around the axle 41, the lever 23 comprising a bore intended to receive the bearing 43.

A fork 44, constituted by a plate of substantially rectangular shape and of which the plane is perpendicular to the axis A of the pivot 38, is keyed in rotation on the part 380 of this pivot. At its end distant from said pivot, the fork 44 comprises a slot 45 open towards said end and adapted to receive a pin 46 borne by a lever 47 of which the plane is parallel to that of the fork 44. This lever 47 is fast in rotation with an axle 48, parallel to that of the pivot 38 and borne by the casing E. This axle 48 cuts the plane passing through the axis of the slide valve 2 and the axis of the rod 29 at a zone comprised, in the direction perpendicular to the axis of the slide valve 2, between the pivoting means 24 and the rod 29.

As seen in FlG. 2, the end of the axle 48 which is distant from the lever 47 is fast to a radial arm 49, parallel to the lever 47, but forming an angle with the latter, in order to be spaced from the lever 23.

There are provided control means C for the displacements of the geometrical pivoting axis A of the lever, sensitive to the pressure of a fluid and advantageously constituted by a jack 50. This jack 50 has its axis parallel to that of the slide valve 2 and is arranged transversely, between this slide valve and the springs R. The rod 51 of the jack 50 passes through a guide bore provided in a wall 52 of the casing E and is connected, at the free end of the arm 49, by a linking part 53 pivoted at its two ends respectively on the rod 51 and on the arm 49. As seen in H0. 2, the part 53 comprises, on the side of the arm 49, a sleeve 53a mounted rotatably on a pivot 54 which is borne by the arm 49. This sleeve 530 has a sufficient length to ensure good maintenance of the part 53. On the side of the rod 51, the part 53 bears a finger 55 parallel to the axle 48 and engaged, free in rotation, in a hole provided at the end of the rod 51.

The jack 50 is of the single acting type and comprises a piston 56 constituted by two cups 56a, 561; between which is clamped a zone of small diameter of a flexible deformable diaphragm 57 with circular edges. The cups 56a, 56b are engaged around the rod 51 and are clamped, against a shoulder 58 of said rod, by a nut 59 screwed on a threaded part, of larger diameter, of the rod 51. The nut 59 serves as a stop for the end of travel against the surface 52a of the wall 52. Shims 59a are placed between the nut 59 and the cup 560, for the adjustment of the travel of the piston 56 and consequently of the final position of the eccentric 41.

The circular outer edge of the diaphragm 57 is constituted by a beading 60 clamped, in fluid-tight manner, between the cylindrical casing 61 of the jack 50, constituted by a part of the casing E, and an end plug 62 fixed on the casing 61 by screws.

This plug 62 comprises a threaded hole, coaxial with the rod 51 into which is screwed a sheath 63 traversed axially by an extension 510, of smaller diameter, of the rod 51. One or several springs 64, serving for the return of the piston 56, are mounted around the rod 51a and compressed between the transverse bottom of the sheath 63 and a washer 65 borne by the threaded end of the rod 510. This washer 65 is stopped by a screwed nut on said threaded part, so that the axial position of this washer 65 is adjustable. A plug 66 is screwed in fluid-tight manner on the sheath 63, so as to cover the end of the rod 510. The bottom of the sheath 63 is traversed by a hole 67 causing the chamber situated on both sides of this bottom to communicate.

The chamber formed between the diaphragm 57 and the plug 62 may receive a fluid under pressure or be placed to the exhaust by means of an assembly 68 (FIG. 2) or passages pierced in the plug 62, on which assembly is screwed an orientable connector 69.

in the case ofa supercharged internal combustion engine, that is to say of which the combustion air is supplied by a turbo-compressor or the like driven by the engine, the air under pressure, serving for the supercharging and delivered by this turbo-compressor, is admitted by the connector 69 into the jack 50. The assembly is then arranged so that an increase in the pressure of the supercharging air causes a displacement of the geometrical axis A of rotation of the lever 23 in a direction such that the slide valve 2 is itself displaced in the direction of an increase of delivery per revolution. In the case of FIG. 1, as indicated by the arrow surmounted by the sign an increase in the flowrate per revolution is obtained for a displacement of the slide valve 2 from right to left with respect to the body 1.

The operation of the regulating device according to the invention is explained below by assuming that it relates to a supercharged engine and that the supercharging air is admitted into the jack 50. It will also be supposed that the cam 37 is turned to the bottom in the anti-clockwise direction according to FIG. 1 (conditions of full load).

On starting, the overload spring 25 separates from the cap 32 the bottom 36 of the bush 35 and the lever 23 is turned to the bottom in clockwise direction, around the axle 41. The slide valve 2 is pushed to the maximum in the direction The flow-rate per revolution of the pump is 0,, (FIG. 4) or overload flow-rate.

The rotary speed of the engine increases progressively, the overload is progressively eliminated so that the delivery per revolution diminishes to the value O (HO. 4).

Up to the present, the rotary speed of the engine is insufficient for the supercharging air to reach the necessary pressure for the displacement of the piston 56. In FIG. 4, it is the segment of the curve p,,, p, which represents the operation of the pump during the elimina tion of the overload.

For a rotary speed N, of the engine, the corrector assembly, comprising especially the pushrod 16, the balls 22 and the cup 19, come into action as described in the above-mentioned patent. The spring 13 is then compressed and the pushrod l6 approaches the cup l9. By reason of the shape of the surfaces 18 and 19a, the balls 22 actuate a displacement of the slide valve 2 in the direction of an increase of delivery per revolution.

in addition, from the speed N the pressure ofthe supercharging air has become sufficient to overcome the effect of the spring 64, so that the piston 56 progres sively approaches the bottom 52 thereby actuating a rotation of the fork 44 in clockwise direction when looking at FIG. 1. This rotation is transmitted to the pivot 38, so that the geometric axis A of rotation of the lever 23, eccentric with respect to the pivot 38, be comes displaced. This displacement is effected from right to left in FIG. 1, so that the upper end 23a of the lever 23 remaining stationary, the lower end 23b is displaced from right to left thereby actuating a displacement of the slide valve 2 in the direction of an increase in the flowrate per revolution.

Two simultaneous phenomena are hence added in favor of an increase in the flow-rate per revolution so that the arc of the curve p,, p; (FIG. 4) representing the variations in flow-rate per revolution for the range of speeds considered will have a relatively high increasing slope.

The piston 56 arrives at the end of its travel for the rotary speed of the engine N before the bush 1] has come into axial abutment against the slide valve 2. The increase in flow-rate per revolution is pursued with a smaller slope until the rotary speed N, for which the bush ll comes into abutment against the slide valve 2. The point representing the operation of the pump is then p of ordinate 0, (FIG. 4).

Up to the speed N, the flow-rate per revolution of the pump remains then practically constant. From the speed N the spring 33 starts to yield so that a displace ment of the slide valve 2 in the direction of reduction in the flow-rate per revolution is produced. The segment of the curve p p of FIG. 4, with a relatively slight negative slope, corresponds to this phase of operation. The point p, has Q; as ordinate.

The speed N represents the cut-off speed for which the assembly of

springs

25, 26 and 27 yields under the action of the centrifugal regulator. The flow-rate per revolution then diminishes rapidly.

Numerous adjustments of the characteristics and of the parameters of the correction device according to the invention are possible.

At the end of the correction brought by the displacement of the geometric axis A, that is to say when the piston 56 has effected it maximum stroke and is in abutment against the surface 520, the adjustment of the flow-rate Q, is obtained by the adjustment of the longitudinal position of the rod 29. This adjustment enables the adjustment of the position of the end 23a of the lever 23.

The adjustment of the flow-rate before correction Q, is obtained by the adjustment of the position of the piston 56, by screwing or unscrewing of the sheath 63 on which the shoulder 58 becomes supported supporting the piston 56.

The adjustment of the speed N,, for which the piston 56 starts to be displaced, is obtained by acting on the initial tension of the spring 64 by displacement of the washer 65 in the longitudinal direction of the rod 51a, by screwing or by unscrewing the nuts serving as a stop to said washer.

The slope of the arc of the curve 2,, p (FIG. 4) may be adjusted by the choice of the stiffness and of the length of the springs 64.

The possibilities of adjustment described in the patent mentioned above for the device comprising the push-rod 16, the cup 19 and the balls 22 are conserved.

It will be noted besides that this device can come into action, according to needs, before, at the same time or after the piston 56, although in the description of the operation given previously, it was supposed that the device came into action at the same time as the piston 56 started to be displaced.

The speed N, can be adjusted by the tension of the spring 33.

The flow-rate 0,, depends on the playj (FIG. 1) adjustable between the cap 32 and the cup 30.

The correction introduced by the pivoting means 24 actuated by the means C depends only on the pressure of the fluid admitted into the jack 50, that is to say, in the case considered more particularly, on the pressure of the air supplied by the turbo-compressor.

The facility of adjustment of the various characteristics and the independance of the adjustments with respect to one another will be noted.

The course of correction due to the pressure of the fluid admitted into the jack 50 is variable as a function of the adjustment of the stroke of the piston 56 and of the eccentricity e (FIG. 2).

A very substantial advantage must be noted, especially at the beginning of the correction, due to the slight effort necessary to make the axis of the eccentric turn which is only to overcome the force of the rotary system.

The fluid correction assembly (jack 50 and pivoting means 24) is integrated with the pump and its adaptation to the assembly of the correction device is easy, which enables all the features and particularities of said pump to be preserved. It is possible in particular to preserve or to adapt the additional correction devices previously described and comprising especially the pushrod 16, the cup 19 and the balls 22 (negative corrector) and the spring 33 (positive corrector).

With the device of the invention, in the case of a supercharged engine, the flow-rate per revolution is adapted to the pressure of the supercharging air, so that the production of smoke is reduced in spite of the inertia of the turbo-compressor which is manifested by a delay in the increase in the pressure of the supercharging air with respect to the increase in the rotary speed of the engine.

However, the invention is not limited to the case of supercharged engines, since the fluid admitted into the jack 50 can be a liquid or a gas supplied by an auxiliary source, the pressure of this fluid being servocoupled to an operating parameter of the engine.

In a modification, the jack 50 could be placed at atmospheric pressure, so that the correction device would enable modification of the flow-rate per revolution of the pump as a function of the external pressure of the air.

I claim:

1. Correction device for the delivery per revolution of a distributing rotary injection pump for an internal combustion engine, which pump comprises: a pump casing, a pump working chamber, a fixed body, and a rotary distributor driven inside said body by a substantially coaxial shaft, which shaft is itself driven by the engine supplied by the pump, delivery means in communication with said pump working chamber and said rotary distributor, said rotary distributor comprising distributing passages inclined to its longitudinal direction and cooperating with said delivery means for varying the delivery per revolution of the pump upon longitudinal displacement of the distributor; a regulator sensitive to the rotary speed of the drive shaft for controlling the longitudinal displacements of the distributor, the distributor being subject, on the one hand, to the action of the regulator through thrust means and, on the other hand, to the contrary action of elastic return means through a transmission lever mounted on pivoting means borne by a casing shielding the pump, said pivoting means comprising a pivot borne by said casing, on which said pivot is mounted in an eccentric manner, a pivoting axle constituting the pivot axis of said lever so as to enable displacement of the pivot axis of the lever upon rotation of said pivot, said correction device comprising a fluid pressure responsive jack with a rod to control the rotation of the pivot, said jack being situated between said distributor and the elastic return means and substantially between planes perpendicular to the axis of the distributor and passing through the ends of said distributor, the axis of the jack being substantially parallel to the axis of the distributor, linking means between the rod and the pivot, said linking means comprising an axle borne by said casing and two radial arms respectively fast in rotation with the ends of the axle, said arms being respectively operatively coupled with the pivot and with the rod.

2. Device according to claim 1 wherein the linking means comprises a linking part connecting one of the arms to the rod, said linking part being pivoted at its two ends respectively on the rod and on the arm, and a fork keyed in rotation on the pivot and including a slot to receive a pin borne by the other arm.

3. Device according to claim 1 wherein the axle cuts the plane passing through the axis of the distributor and the axis of a rod (29) bearing the elastic return means.

4. Device according to claim 1 wherein the rod of the jack comprises an extension passing through an end borne by a yoke fixed on the casing, said pivot comprising two coaxial cylindrical outer parts, of different diameters, borne by the flanges of the yoke, the material pivoting axle of said lever, eccentric with respect to the pivot, being constituted by an intermediate part comprised between said cylindrical parts and situated between the flanges of the yoke.

i i i i

Claims

4. Device according to claim 1 wherein the rod of the jack comprises an extension passing through an end plug, said extension being lodged in a sheath which is adjustable along its axis, and elastic return means for the piston of the jack are provided between a washer borne by the end of the extension in an adjustable manner along its axis, and the bottom of the sheath.

5. Device according to claim 1 wherein the jack has a casing constituted by a part of the pump casing.

6. Device according to claim 1, wherein the pivot is borne by a yoke fixed on the casing, said pivot comprising two coaxial cylindrical outer parts, of different diameters, borne by the flanges of the yoke, the material pivoting axle of said lever, eccentric with respect to the pivot, being constituted by an intermediate part comprised between said cylindrical parts and situated between the flanges of the yoke.