EP1183466B1 - Improved high pressure pump - Google Patents

Description

The present invention relates to a high pressure pump for feeding as fuel for an internal combustion engine of a motor vehicle. In this case, the liquid transferred is the fuel.

We already know in the prior art a high pressure pump for pumping of a first liquid, called transferred liquid, of the type comprising a unit main pumping of the transferred liquid operated by a secondary unit of pumping a second liquid, called working liquid, the secondary unit comprising at least minus a working liquid compression piston provided with an axial bore of circulation of working liquid between a reservoir and a compression chamber of working liquid, this compression chamber being delimited by a flexible membrane pumping liquid transferred arranged in the main unit.

A pump of this type is described for example in WO 97/47883.

The working liquid compression piston described in this document comprises a swiveling head in which is formed a through end of the axial drilling. This swiveling head bears against an inclined face of the bias plate by means of a sliding shoe pierced so as to allow the passage of working fluid. A recess in the inclined face of the plate allows, depending on the relative position of this recess and the shoe, to alternate during the rotation of the plate the communication of the axial bore of the piston with the tank and the isolation of this axial drilling relative to this tank.

To make the pump work satisfactorily, the recess in the the bias plate must be precisely dimensioned. If this precision is not observed, undesirable pressure pulses are observed in the main unit and secondary pumping. However, the precision required is not always compatible with manufacturing tolerances and dimensional variations generally accepted in conditions for mass production of the pump.

In addition, the use of sliding pads poses problems dynamic sealing.

Finally, the membrane delimiting the compression chamber is usually resiliently returned by a spring to a position tending to reduce the volume of this compression chamber. For reasons of efficient operation of the pump mentioned above, the diaphragm return spring must be sized with precision which is hardly compatible with a mass production of the pump.

The object of the invention is to propose a high pressure pump, of the type above, simple to manufacture and very reliable.

To this end, the invention relates to a high pressure pump, of the type cited above, the piston of which includes a valve for closing the axial bore, housed in this hole between two ends of this hole in permanent communication with the reservoir and the compression chamber respectively, the valve opening as soon as the pressure of the working liquid in the tank exceeds that of the working liquid in the compression chamber and closing otherwise and in that the membrane separates the compression chamber from a pumping chamber liquid transferred at variable volume, the membrane being movable between a first position of maximum volume of the pumping chamber, towards which this membrane is spring-loaded by a spring, called a membrane spring, and a second position of minimum volume of the pumping chamber, the stiffness of the diaphragm spring being dimensioned so that this diaphragm spring holds the working liquid contained in the compression chamber under overpressure relative to the working liquid contained in the reservoir, as long as the membrane has not reached its first position,

• le perçage est étagé et comprend un tronçon de grand diamètre, débouchant dans la chambre de compression; et un tronçon de petit diamètre, débouchant dans le réservoir, le clapet comprenant une bille logée dans le tronçon de grand diamètre de façon à être déplaçable entre, d'une part, un épaulement séparant les tronçons de grand et petit diamètres, formant un siège de fermeture du clapet, et d'autre part, une butée de limitation de la course d'ouverture du clapet ;
• la chambre de compression est ménagée dans un corps de l'unité secondaire dans lequel le piston est monté coulissant, ce piston comportant une extrémité externe au corps rappelée élastiquement au contact d'une butée à roulement portée par un plateau biais d'actionnement du piston ;

According to other characteristics of the invention:

• the bore is stepped and comprises a section of large diameter, opening into the compression chamber; and a small diameter section, opening into the reservoir, the valve comprising a ball housed in the large diameter section so as to be movable between, on the one hand, a shoulder separating the large and small diameter sections, forming a seat closing the valve, and secondly, a stop limiting the opening stroke of the valve;
• the compression chamber is formed in a body of the secondary unit in which the piston is slidably mounted, this piston having an end external to the body elastically biased in contact with a rolling stop carried by a bias actuation plate of the piston ;

• la figure 1 est une vue de face d'un pompe à haute pression selon l'invention;
• la figure 2 est une vue en coupe suivant la ligne 2-2 de la figure 1 ;
• la figure 3 est une vue en coupe suivant la ligne 3-3 de la figure 1 ;
• la figure 4 est une vue de détail de la figure 2 dans laquelle le plan de coupe a été légèrement décalé de façon à passer par l'axe de la vis représentée sur ces figures 2 et 4;
• la figure 5 est une vue de détail de la partie entourée 5 de la figure 3 montrant un bouchon d'obturation de moyens de remplissage d'un réservoir de la pompe dans une position de pré-obturation ;
• la figure 6 est une vue similaire à la figure 5 représentant une première variante du bouchon ;
• la figure 7 est une vue similaire à la figure 3 représentant une seconde variante du bouchon ;
• les figures 8 à 11 sont des vues similaires à la figure 2 représentant quatre variantes respectivement d'un moyeu de la pompe selon l'invention.

The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the drawings in which:

• Figure 1 is a front view of a high pressure pump according to the invention;
• Figure 2 is a sectional view along line 2-2 of Figure 1;
• Figure 3 is a sectional view along line 3-3 of Figure 1;
• Figure 4 is a detail view of Figure 2 in which the cutting plane has been slightly offset so as to pass through the axis of the screw shown in these Figures 2 and 4;
• FIG. 5 is a detail view of the surrounded part 5 of FIG. 3 showing a closure plug for filling means of a reservoir of the pump in a pre-closure position;
• Figure 6 is a view similar to Figure 5 showing a first variant of the plug;
• Figure 7 is a view similar to Figure 3 showing a second variant of the plug;
• Figures 8 to 11 are views similar to Figure 2 showing four variants respectively of a pump hub according to the invention.

There is shown in Figures 1 to 3 a high pressure pump according to the invention, designated by the general reference 12. In the example described, the pump 12 is intended for supplying high pressure fuel to an internal combustion engine of motor vehicle. The pump 12 is therefore intended to pump a first liquid, to know fuel in the example described, called transferred liquid.

In Figure 1 we recognize a connector 14 for connecting the pump 12 to a Fuel tank.

With particular reference to Figures 2 and 3, it can be seen that the pump 12 comprises a housing 16 of generally cylindrical shape, of axis X, in which are arranged a main unit 18 for pumping fuel and a secondary unit 20 for pumping a second conventional liquid, for example a mineral oil, called liquid job. The main unit 18 is operated by the secondary unit 20 according to principles general operating methods described for example in WO 97/47883.

The housing 16 comprises a body 22, of generally cylindrical shape, surrounding the secondary unit 20, and a cover 24, of generally cylindrical shape, surrounding the unit main 18. The body 22 of the housing and the cover 24 respectively form two opposite ends of the housing 16.

The housing body 22 is connected to the cover 24 by at least one screw 26, by example three screws 26. Each screw 26, preferably of steel, extends substantially parallel to the X axis. A screw 26 will be described in more detail later.

Inside the housing 16, the main unit 18 is separated from the unit secondary 20 by a separation disc 28 centered substantially on the X axis. This disc 28 is preferably made of steel or cast iron.

The main unit 18 comprises at least one flexible membrane 30 of pumping fuel, for example three membranes 30 as in the example illustrated. It will be noted that only two membranes 30 are shown in the figures, especially in Figure 3.

The membrane 30 separates a fuel pumping chamber 32, arranged in the main unit 18, a working liquid compression chamber 34, arranged in the secondary unit 20. The volume of the pumping chamber 32 is variable. The compression chamber 34 is partially provided in the separation disc 28.

Each pumping chamber 32 is associated with a suction valve 36 for fuel and a fuel delivery valve 38. These valves 36, 38, of structure and conventional operating systems, are carried by a body 40 housed in the cover 24 between a bottom of the latter and the separation disc 28.

For the sake of lightening the pump 12, the body 22 of the housing, the cover 24 and the valve body 40 are made of aluminum or an aluminum-based alloy or yet another equivalent light metal.

The valves 36, 38 are connected in a manner known per se to the pumping 32 corresponding to a safety valve 42 of structure and conventional operation.

Conventionally, each membrane 30 is movable between a first maximum volume position of the pumping chamber 32, as shown in particular in FIGS. 2 and 3, and a second position of minimum volume of this pumping chamber (not shown in the figures). The displacements of the membrane 30 are imposed in particular by the secondary unit 20 and control the opening and closing fuel suction and delivery valves 36, 38.

Each membrane 30 is constantly spring-loaded towards its first position by a spring 44, called a membrane spring.

Each valve 36, 38 communicates, on the one hand, with a chamber 46 fuel suction and, on the other hand, a fuel delivery chamber 48. The suction chamber 46 is connected in a manner known per se to the connection 14 for supplying fuel.

The fuel suction 46 and discharge 48 chambers are delimited, at least in part, by facing surfaces 50, 52, of general shape cylindrical, with an axis substantially coinciding with the axis X. A first surface 50 forms an inner surface of the cover 24. The second surface 52 forms a surface device of the valve body 40.

The facing surfaces 50, 52 include two shoulders complementary 50E, 52E in contact with each other so as to form a watertight joint plane separating the suction 46 and discharge 48 chambers. This parting line is substantially perpendicular to the X axis. The shoulders 50E, 52E form a seal effective metal-to-metal seal.

It will be noted that the suction chamber 46, in which the pressure is more weak than in the discharge chamber 48, is delimited by the bottom of the cover 24 whose thickness is relatively small. On the other hand, the discharge chamber 48 is delimited by a peripheral wall of the cover 24 thicker than the bottom of this cover, so as to resist the high pressure reached by the fuel circulating in this delivery chamber.

The secondary unit 20 comprises a piston 54 for compressing liquid of work associated with each membrane 30 and intended to move this membrane 30 between its two positions. Thus, in the example described, the secondary unit 20 has three pistons 54 only two of which are visible in the figures, in particular in FIG. 3.

The piston 54 is slidably mounted in a body 56, preferably of steel or cast iron, so as to be movable substantially parallel to the axis X. The piston 54 extends between the working liquid compression chamber 34, partly arranged in the piston body 56, and a reservoir 58 of working liquid.

The end of the piston 54; external to the piston body 56, is recalled elastically by a spring 59 in contact with a rolling stop, for example a stop with needles 60, carried by a bias plate 62 for actuating the pistons 54. This plate bias is carried by a hub 64 of the secondary unit 20. This hub 64 is rotatably mounted around the X axis in the housing body 22 forming a bearing. The bias plate 62 turns around the X axis jointly with the hub 64, the latter being connected to means classic drives by an Oldham type 66 seal. The liquid tightness of work between the housing body 22 and the hub 64 is ensured by conventional means comprising in particular an annular seal 67 made of elastomer. The hub 64 will be described more in detail later.

Note that the separation disc 28 and the piston body 56 form a intermediate assembly EI sandwiched axially between a skirt 22J of the body 22 of the housing, internal to the cover 24, and the valve body 40. Furthermore, with particular reference to Figure 4, we see that each screw 26 is provided with a head 26T and a threaded body 26C. The 26T head is supported on a passing seat 68 formed in the body 22 of the housing. The body 26C thread is screwed into a threaded hole 70 formed in an ear 72 integral with the cover 24. Therefore, the housing body 22, the intermediate assembly EI and the body 40 valves are clamped between the head 26T of the screw and the joint plane materialized by the shoulders 50E, 52E.

Preferably, the axial dimension L1 of the intermediate assembly EI is substantially equal to the length L2 of the part of the body 26C of the screw extending between the 26T head of this screw and the tapped hole 70. In this way, the expansions of the different materials, namely, on the one hand. aluminum or light metal and, on the other hand, steel or cast iron, are substantially identical inside and outside of the housing 16.

Referring again to Figures 2 and 3, we see that the piston 54 is provided an axial bore 74 through which the working liquid can circulate between the reservoir 58 and the compression chamber 34. A first end of the bore 74, inside the piston body 56, communicates permanently with the compression chamber 34. The second end of the bore 74, external to the piston body 56, communicates in permanently with the reservoir 58.

Preferably, the bore 74 is stepped and comprises a section 74A of large diameter, opening into the compression chamber 34, and a section 74B of small diameter, opening into the tank 58.

A ball, forming a valve 76, is housed in the section 74A of large diameter so as to be movable, on the one hand, between an E74 shoulder, separating the sections 74A and 74B, forming a seat for closing the valve 76, and on the other hand, a stop 78 for limiting the opening stroke of this valve 76.

The valve 76 opens as soon as the pressure of the working liquid in the tank 58 exceeds that of the working liquid in the compression chamber 34. In the case on the contrary, the valve 76 closes so as to close the bore 74.

For the proper functioning of the pump 12, the stiffness of the return spring 44 of the membrane 30 associated with the piston 54 is dimensioned so that this spring 44 maintain the working liquid contained in the compression chamber 34 in overpressure relative to the working liquid contained in the reservoir 58, this as long as the membrane 44 has not reached its first position of maximum volume of the pumping 32.

We will indicate below some particular characteristics of the operation of the main 18 and secondary 20 pumping units, the main unit 18 operating according to the principles of a positive displacement pump.

When the bias plate 62 pushes the piston 54 into the piston body 56 (displacement of the piston 54 to the right considering Figures 2 and 3), the liquid work contained in the compression chamber 34 is compressed (overpressure by relative to the liquid contained in the reservoir 58), so that the valve 76 closes and the flexible membrane 30 moves to its second position of minimum volume of the pumping chamber 32. This causes, as is conventional, the backflow of the high pressure fuel in the discharge chamber 48.

When the bias plate 62 allows the piston 74 to move in one direction opposite to the previous one (to the left when considering Figures 2 and 3), under the effect of return spring 59, the membrane 30 is returned by the spring 44 in its first position of maximum volume of the pumping chamber 32. This causes, like this is conventional, the suction of the fuel, coming from the suction chamber 46, in the pumping chamber 32.

Note that the membrane spring 44 allows the automatic return of the membrane 30 in its first position, this even in the absence of fuel in the main pumping unit 18. Furthermore, when the piston 54 moves towards the left considering Figures 2 and 3, given the leakage of working liquid between the compression chamber 34 and the reservoir 58, the membrane 30 reaches its first position before the piston 54 completes its stroke to the left. Therefore, once as the membrane 30 reaches its first position, the pressure of the working liquid in the compression chamber 34 drops compared to that of the working liquid in the tank 58, which opens the valve 76 and replenishes the compression chamber 34 in working liquid so as to compensate for leaks.

We will describe below, with particular reference to Figures 3 and 5, simple and effective means allowing the tank 58 to be completely filled with working fluid.

These filling means comprise a filling neck 80, connected to reservoir 58, closable by a plug 82.

In the example illustrated in FIGS. 3 and 5, the plug 82 is intended to cooperate by screwing with the neck 80. The plug 82 has a blind hole 84, substantially axial, communicate via a hole 86 in the plug, substantially radial, with a peripheral recess 88 of the plug extended axially by a sealing surface 90 of this plug intended to cooperate with a seat shutter 92 formed in the end of the neck 80 near the reservoir 58.

Preferably, the shutter surface 90 and the shutter seat 92 have general conical shapes, the sealing surface 90 converging towards the seat shutter 92.

The plug 82 is movable in the neck 80, by screwing, between a position pre-sealing of the reservoir 58, in which the sealing surface 90 is spaced from the seat 92, above this seat 92, as shown in FIG. 5, and a the closed position of this reservoir 58, in which the closed surface 90 is in tight contact with the seat 92, as shown in FIG. 3.

The neck 80 is likely to contain an overflow of working liquid in excess of the reservoir, the level N of this overflow extending into the neck 80 above the seat 92.

It will be noted that, when the plug 82 is in its pre-sealing position, the peripheral recess 88 of this plug communicates with the reservoir 58, so that the blind hole 84 forms a receptacle for the overflow of working liquid. Otherwise, in the presence of the overflow in the neck 80, the plug 82 is movable in this neck between its pre-shutter and shutter positions.

To move the plug 82, the latter is provided with an 82T operating head. through which the open end of the blind hole 84 opens. The head 82T is bounded by a polygonal inner surface 82I allowing the operation of the plug 82 using a conventional tool.

Alternatively, the 82T operating head can be delimited by a surface polygonal exterior 82E as shown in FIG. 6, for the maneuver plug 82 using a conventional tool.

The plug 82 carries an O-ring peripheral seal 93 positioned axially between the head 82T and the recess 88. This seal 93 provides sealing between the neck 80 and the plug 82 above the recess 88.

The plug 82 makes it possible to fill the reservoir 58 under vacuum of the following way.

Initially, the plug 82 is screwed into the neck 80 in its pre-sealing position as shown in Figure 5.

To fill the reservoir 58 with working liquid, a vacuum is created in this reservoir, using conventional means, then the working liquid is introduced through the hole blind 84 of the plug. In this way, the working liquid flows into the reservoir 58 in circulating in the blind hole 84, the radial bore 86 and the recess 88.

The filling of the reservoir 58 is continued until too much remains full in the neck 80 and the blind hole 84, as shown in FIG. 5.

Finally, in the presence of the overflow, the plug 82 is moved by screwing up its closed position as shown in Figure 3. The reservoir 58 is then isolated of the filling neck 80, the quantity of working liquid remaining in the blind hole 84 being easily evacuated by the end of the blind hole 84 emerging through the head of maneuver 82T.

Referring to Figure 3, it will be noted that the reservoir 58 is connected to conventional means 94 for compensating for the expansion of the working liquid contained in the reservoir 58. These means comprise a flexible membrane 96 separating a channel 98 of communication of the membrane 96 with the working liquid of the reservoir 58 and a space 100 for release of the membrane 96 protected by a shell 102 of shape general hemispherical. The membrane 96 deforms according to the variations of the volume of working liquid contained in the reservoir 58.

In FIG. 7, an alternative embodiment of the plug 82 has been shown.

In this case, the plug 82 comprises a ball 104 that can be moved forcibly between a pre-sealing position of the reservoir 58, as shown in dashed lines on the Figure 7, and a closed position of the reservoir 58, as shown in solid lines in this figure 7.

The surface of the ball 104 forms the sealing surface intended to cooperate with tightly with the seat 92 of the neck.

The filling neck 80 is closed by means of the ball 104. the following way.

In the presence of the overflow of working liquid, the level N of which is shown in phantom in Figure 7, the ball 104 is placed in its pre-sealing position as shown in phantom in this figure 7. Then, the ball is forced to move 104 in the neck 80 so as to press it against the seat 92, as shown in solid line in Figure 7.

Note that during the forced movement of the ball 104 between its tank pre-shutter and shutter positions 58, the overflow of work, forced into the reservoir 58 under the effect of the movement of the ball 104, is compensated by the deformation of the membrane 96 of the compensation means expansion 94, as shown in Figure 7.

The hub 64 will be described below in more detail with reference to FIG. 3.

In the example illustrated in this FIG. 3, the hub 64 comprises a sleeve 106, with an axis coinciding with the X axis, in which the bias plate 62 is housed.

The hub 64 also includes a ring 108 fixed on the external surface of sleeve 106.

The outer surface of the sleeve 106 forms a cylindrical surface peripheral SG for guiding the hub in rotation in the body 22 of the housing. A face of the ring 108 forms a shoulder FE for axial positioning of the hub 64 relative to to the body 22 of the housing.

Furthermore, the body 22 of the housing comprises a jacket 110 whose surface internal forms a cylindrical surface of range SP in sliding contact with the surface SG guide device of the hub.

The housing body 22 also comprises a washer 112, arranged at a end of the jacket 110, provided with a face forming a flat surface of bearing FP in sliding contact with the FE shoulder of the hub.

The jacket 110 and the washer 112 are fixed in a manner known per se on the body 22 of housing and are made of conventional materials, preferably low coefficient of friction.

It will be noted that the shoulder FE of the hub 64, extending the surface of SG guide of this hub, is urged to bear against the bearing face FP of the body 22 of case by the elastic return force of the pistons 54 in contact with the needle stopper 60 as well as by the pressure of the working liquid in contact with the bias plate 62.

According to a first variant shown in Figure 8, the cylindrical surface SP is formed by the internal surface of a sleeve 114, carried by the body 22 of housing, provided with an end extended by a flange 116 delimiting the flat surface of FP range.

According to a second variant shown in FIG. 9, the peripheral surface guide SG of the hub is formed by the external surface of a sleeve 118, in which is housed the bias plate 62, provided with an end extended by a flange 120 delimiting the axial positioning shoulder FE of the hub. Sleeve 118 of hub cooperates with a sleeve 114 secured to the body 22 of the housing of the type shown in figure 8.

According to third and fourth variants shown in Figures 10 and 11 respectively, the peripheral guide surface SG and the positioning shoulder axial FE of the hub are formed by the external surface of a stepped tubular member 122, in a single piece, in which the bias plate 62 is housed. The stepped member 122 can be easily produced in a conventional manner, in particular by stamping, processing and rectification.

In the third variant shown in FIG. 10, the stepped member 122 is in sliding contact with a cylindrical surface of SP range and a flat surface of FP range provided on elements similar to those shown in FIG. 3.

In the fourth variant shown in Figure 11, the surface guide device SG of the stepped member 122 is in contact with bearing 124 extending substantially parallel to the axis X, and the shoulder of axial positioning FE is in contact with rolling needles 126, extending substantially radially with respect to the X axis.

The needles 124, 126 are carried by cages 128, 130 fixed so known per se on the body 22 of the housing.

Among the advantages of the invention, the following will be noted.

The high pressure pump according to the invention, simpler to manufacture than that of the state of the art described in WO 97/47883 (note in particular the absence of a skid slip between the pistons and the bias plate, the absence of a recess in the plate bias, etc ...), is less sensitive to wear and of a reduced cost.

The valve piston of the pump according to the invention makes it possible to avoid pulsations pressure observed in the prior art pump, in particular because the performance of the pump according to the invention does not depend on a compromise between the dimensions of the recess of the bias plate of the prior art pump and of the diaphragm return spring associated with each piston.

Claims (3)

1. The high-pressure pump for supplying a motor vehicle internal combustion engine with fuel, the fuel forming the transferred liquid, of the type comprising a main unit (18) for pumping the transferred liquid, which unit is actuated by a secondary unit (20) for pumping a second liquid, known as the working liquid, the secondary unit comprising at least one piston (54) for compressing the working liquid, equipped with an axial drilling (74) for collecting leaks of working liquid between a reservoir (58) and a working-liquid compression chamber (34), this compression chamber (34) being delimited by a flexible diaphragm (30) for pumping transferred liquid, this diaphragm being arranged in the main unit (18), the diaphragm (30) separating the compression chamber (34) from a variable-volume pumping chamber (32) for the transferred liquid, the diaphragm (30) being moveable between a first position in which the pumping chamber (32) has maximum volume, towards which position this diaphragm is elastically returned by a spring (44) known as the diaphragm spring, and a second position in which the pumping chamber (32) has minimum volume, characterized in that the piston (54) comprises a valve (76) for shutting off the axial drilling (74) and housed in this drilling between two ends of this drilling in permanent communication with the reservoir (58) and the compression chamber (34) respectively, the valve (76) opening as soon as the pressure of the working liquid in the reservoir (58) exceeds that of the working liquid in the compression chamber (34) and closing if the reverse is true, and in that the stiffness of the diaphragm spring (44) being chosen so that this diaphragm spring (44) keeps the working liquid contained in the compression chamber (34) at a raised pressure with respect to the working liquid contained in the reservoir (58) for as long as the diaphragm (30) has not reached its first position.
2. Pump according to Claim 1, characterized in that the drilling (74) is stepped and comprises a large-diameter portion (74A) opening into the compression chamber (34) and a small-diameter portion (74B) opening into the reservoir (58), the valve comprising a ball (76) housed in the large-diameter portion (74A) so as to be able to be moved between, on the one hand, a shoulder (E74) separating the large-diameter and small-diameter portions, forming a seat onto which the valve (76) closes and, on the other hand, a stop (78) that limits the opening travel of the valve.
3. Pump according to Claim 1 or 2, characterized in that the compression chamber (34) is formed in a body (56) of the secondary unit (20) in which body the piston (54) is slidably mounted, this piston (54) comprising an end external to the body (56) returned elastically into contact with a thrust rolling bearing (60) carried by a swashplate (62) for actuating the piston (54).

Images