Abstract:
The invention concerns a pump for pumping a first liquid, called transferred liquid, and comprising a main unit ( 18 ) for pumping the transferred liquid actuated by an auxiliary unit ( 20 ) pumping a second liquid, called working liquid. The main ( 18 ) and auxiliary ( 20 ) units are housed in a casing ( 16 ) generally cylindrical in shape. The main unit ( 18 ) comprises at least two valves ( 36, 38 ), for respectively sucking up and delivering the transferred liquid, borne by a valve body ( 40 ) housed in the casing ( 16 ). Each valve ( 36, 38 ) communicates with two chambers, respectively a suction chamber ( 46 ) and a delivery chamber ( 48 ) for the transferred liquid, defined by opposite surfaces (50, 52) provided in the valve body ( 40 ) and the casing ( 16 ). Said surfaces ( 50, 52 ) comprise two matching shoulders ( 50 E,  52 E) pressed against each other so as to form a tight joint plane separating the suction chamber ( 46 ) and the delivery chamber ( 48 ). The invention is applicable to a high pressure pump for supplying a motor vehicle engine with fuel.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a high-pressure pump with improved sealing. 
     It applies in particular to a high-pressure pump for supplying a motor vehicle internal combustion engine with fuel. In this case, the transferred liquid is the fuel. 
     BACKGROUND OF THE INVENTION 
     The state of the art already discloses a high-pressure pump for pumping a first liquid, known as the transferred liquid, of the type comprising a main unit for pumping the transferred liquid and actuated by a secondary unit for pumping a second liquid, known as the working liquid, and of the type comprising a housing of cylindrical overall shape, in which the main and secondary units are arranged, the main unit comprising at least two valves, namely an intake valve and a delivery valve for the transferred liquid, carried by a valve body housed in the housing, each valve communicating with two chambers, namely an intake chamber and a delivery chamber for the transferred liquid, delimited by opposing surfaces of cylindrical overall shape, of axis coinciding more or less with that of the housing, formed in the valve body and in the housing. 
     BRIEF DESCRIPTION OF THE INVENTION 
     A pump of this type is described, for example, in WO 97/47883. 
     In the pump described in that document, the intake and delivery chambers connected to the valves are separated by a rubber O-ring seal. This seal, housed in an annular groove formed in a peripheral surface of the valve body, is relatively bulky. 
     A particular object of the invention is to propose a high-pressure pump, of the aforementioned type, equipped with means which are effective and not very bulky for separating the intake and delivery chambers. 
     To this end, the subject of the invention is a high-pressure pump of the aforementioned type, characterized in that the opposing surfaces comprise two complementary shoulders bearing on one another so as to form a sealed joining plane separating the intake and delivery chambers. 
     According to other features of the invention: 
     the housing comprises a body and a cover forming the respective two opposite ends of this housing, the housing body being connected to the cover by at least one screw more or less parallel to the axis of the housing, having a head bearing on a seat formed in the housing body, and a threaded body screwed into a tapped orifice in the cover, the pump additionally comprising an intermediate assembly clamped axially between a skirt of the housing body, internal to the cover, and the valve body so that the housing body, the intermediate assembly and the valve body are clamped between the head of the screw and the joining plane; 
     the intermediate assembly comprises a body in which a piston of the secondary unit is mounted so that it can slide, this piston being intended to compress the working liquid; 
     the housing and the valve body are made of a lightweight metal such as aluminum or of an aluminum-based alloy; 
     the intermediate assembly is made of steel or cast iron and the screw is made of steel, the axial dimension of the intermediate assembly being more or less equal to the length (L 2 ) of the part of the body of the screw extending between the head of this screw and the tapped orifice of the cover; and 
     the transferred liquid is a fuel for a motor vehicle internal combustion engine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood from reading the description which will follow, given solely by way of example and made with reference to the drawings in which: 
     FIG. 1 is a front view of a high-pressure pump according to the invention; 
     FIG. 2 is a view in section on the line  2 — 2  of FIG.  1 ;, 
     FIG. 3 is a view in section on the line  3 — 3  of FIG. 1; 
     FIG. 4 is a detail view of FIG. 2, in which the section plane has been offset slightly to make it pass through the axis of the screw depicted in these FIGS. 2 and 4; 
     FIG. 5 is a detail view of the ringed portion  5  of FIG. 3, showing a plug that stoppers means of filling a reservoir of the pump in a prestoppering position; 
     FIG. 6 is a view similar to FIG. 5, depicting a first variant of the plug; 
     FIG. 7 is a view similar to FIG. 3, depicting a second variant of the plug; 
     FIGS. 8 to  11  are views similar to FIG. 2, depicting four respective variants of a hub of the pump according to the invention. 
    
    
     FIGS. 1 to  3  depict a high-pressure pump according to the invention, denoted by the general reference  12 . In the example described, the pump  12  is intended to supply a motor vehicle internal combustion engine with fuel at high pressure. The pump  12  is therefore intended to pump a first liquid, namely fuel in the example described, known as the transferred liquid. 
     Visible in FIG. 1 is a connection  14  intended to connect the pump  12  to a fuel tank. 
     With more particular reference to FIGS. 2 and 3, it can be seen that the pump  12  comprises a housing  16  of cylindrical overall shape, of axis X, in which are arranged a main unit  18  for pumping fuel and a secondary unit  20  for pumping a conventional second liquid, for example a mineral oil, known as the working liquid. The main unit  18  is actuated by the secondary unit  20 , according to the general conventional operating principles described, for example, in WO 97/47883. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The housing  16  comprises a body  22 , of cylindrical overall shape, surrounding the secondary unit  20 , and a cover  24 , of cylindrical overall shape, surrounding the main unit  18 . The housing body  22  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 , for example three screws  26 . Each screw  26 , preferably made of steel, extends more or less parallel to the axis X. A screw  26  will be described in greater detail later. 
     Inside the housing  16 , the main unit  18  is separated from the secondary unit  20  by a separating disk  28  centered more or less on the axis X. This disk  28  is preferably made of steel or cast iron. 
     The main unit  18  comprises at least one flexible diaphragm  30  for pumping fuel, for example three diaphragms  30 , as in the example illustrated. It will be noted that just two diaphragms  30  are depicted in the figures, particularly in FIG.  3 . 
     The diaphragm  30  separates a fuel-pumping chamber  32 , arranged in the main unit  18 , from a chamber  34  for compressing the working liquid, arranged in the secondary unit  20 . The volume of the pumping chamber  32  is variable. The compression chamber  34  is formed partially in the separating disk  28 . 
     Associated with each pumping chamber  32  are a fuel intake valve  36  and a fuel delivery valve  38 . These valves  36 ,  38 , of conventional structure and operation, are carried by a body  40  housed in the cover  24  between an end wall thereof and the separating disk  28 . 
     To make the pump  12  lighter, the housing body  22 , the cover  24  and the valve body  40  are made of aluminum or aluminum-based alloy, or alternatively from some other equivalent lightweight metal. 
     The valves  36 ,  38  are connected in a way known per se to the corresponding pumping chamber  32  and to a safety valve  42  of conventional structure and operation. 
     In the conventional way, each diaphragm  30  can move between a first position in which the pumping chamber  32  has maximum volume, as depicted in particular in FIGS. 2 and 3, and a second position in which this pumping chamber has minimum volume (this position is not depicted in the figures). The movements of the diaphragm  30  are dictated in particular by the secondary unit  20  and control the opening and closing of the fuel intake and delivery valves  36 ,  38 . 
     Each diaphragm  30  is constantly elastically returned to its first position by a spring  44  known as the diaphragm spring. 
     Each valve  36 ,  38  communicates, on the one hand, with a fuel intake chamber  46  and, on the other hand, with a fuel delivery chamber  48 . The intake chamber  46  is connected, in a way known per se, to the fuel supply connection  14 . 
     The fuel intake  46  and delivery  48  chambers are delimited, at least in part, by opposing surfaces  50 ,  52 , of cylindrical overall shape, of an axis coinciding more or less with the axis X. A first surface  50  forms an internal surface of the cover  24 . The second surface  52  forms a peripheral surface of the valve body  40 . 
     The opposing surfaces  50 ,  52  comprise two complementing shoulders  50 E,  52 E bearing against one another so as to form a sealed joining plane separating the intake  46  and delivery  48  chambers. This joining plane is more or less perpendicular to the axis X. The shoulders  50 E,  52 E form an effective metal-to-metal seal. 
     It will be noted that the intake chamber  46 , in which the pressure is lower than it is in the delivery chamber  48 , is delimited by the end wall of the cover  24 , the thickness of which is relatively small. By contrast, the delivery chamber  48  is delimited by a peripheral wall of the cover  24  which is thicker than the end wall of this cover, so as to withstand the high pressure reached by the fuel flowing through this delivery chamber. 
     The secondary unit  20  comprises a piston  54  for compressing the working liquid, this piston being associated with each diaphragm  30  and intended to move this diaphragm  30  between its two positions. Thus, in the example described, the secondary unit  20  has three pistons  54 , just two of which are visible in the figures, particularly in FIG.  3 . 
     The piston  54  is mounted so that it can slide in a body  56 , preferably made of steel or cast iron, so that it can be moved more or less parallel to the axis X. The piston  54  extends between the chamber  34  for compressing the working liquid, formed partly 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 returned elastically by a spring  59  into contact with a thrust rolling bearing, for example a thrust needle bearing  60 , borne by a swashplate  62  that operates the pistons  54 . This swashplate is carried via a hub  64  of the secondary unit  20 . This hub  64  is mounted so that it can rotate about the axis X in the housing body  22  which forms a bearing mount. The swashplate  62  revolves about the axis X together with the hub  64 , the latter being connected to conventional drive means by a coupling  66  of the Oldham type. Sealing against the working liquid between the housing body  22  and the hub  64  is provided by conventional means comprising, in particular, an annular seal  67  made of elastomer. The hub  64  will be described in greater detail later. 
     It will be noted that the separating disk  28  and the piston body  56  form an intermediate assembly EI clamped axially between a skirt  22 J of the housing body  22 , internal to the cover  24 , and the valve body  40 . Furthermore, referring in particular to FIG. 4, it can be seen that each screw  26  has a head  26 T and a threaded body  26 C. The head  26 T bears against a seat  68  formed in the housing body  22 . The threaded body  26 C is screwed into a tapped orifice  70  made in a lug  72  secured to the cover  24 . As a result of this, the housing body  22 , the intermediate assembly EI and the valve body  40  are clamped between the head  26 T of the screw and the joining plane embodied by the shoulders  50 E,  52 E. 
     As a preference, the axial dimension Ll of the intermediate assembly EI is more or less equal to the length L 2  of the part of the body  26 C of the screw that extends between the head  26 T of this screw and the tapped orifice  70 . Thus, the extensions of the various materials, namely, on the one hand, the aluminum or the lightweight metal and, on the other hand, the steel or cast iron, are more or less the same inside and outside the housing  16 . 
     Referring once again to FIGS. 2 and 3, it can be seen that the piston  54  has an axial bore  74  through which the working liquid can flow between the reservoir  58  and the compression chamber  34 . A first end of the bore  74 , internal to 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 permanently with the reservoir  58 . 
     As a preference, the bore  74  is stepped and has a large-diameter portion  74 A, opening into the compression chamber  34 , and a small-diameter portion  74 B, opening into the reservoir  58 . 
     A ball, forming a valve  76 , is housed in the large-diameter portion  74 A so that it can be moved, on the one hand, between a shoulder E 74  separating the portions  74 A and  74 B, forming a seat for closing the valve  76  and, on the other hand, a stop  78  that limits the opening travel of this valve  76 . 
     The valve  76  opens as soon as the pressure of the working liquid in the reservoir  58  exceeds that of the working liquid in the compression chamber  34 . If the reverse is true, the valve  76  closes so as to close off the bore  74 . 
     For the pump  12  to work correctly, the stiffness of the return spring  44  for the diaphragm  30  associated with the piston  54  is rated so that this spring  44  keeps the working liquid contained in the compression chamber  34  at a raised pressure compared with the working liquid contained in the reservoir  58 , this being as long as the diaphragm  44  has not reached its first position in which the pumping chamber  32  has its maximum volume. 
     A few particular characteristics of the operation of the main  18  and secondary  20  pumping units will be indicated hereinbelow, the main unit  18  operating according to the principles of a positive-displacement pump. 
     When the swashplate  62  drives the piston  54  into the piston body  56  (moving the piston  54  to the right when considering FIGS.  2  and  3 ), the working liquid contained in the compression chamber  34  is compressed (to a raised pressure compared with the liquid contained in the reservoir  58 ) so that the valve  76  closes and the flexible diaphragm  30  moves toward its second position in which the pumping chamber  32  has its minimum volume. This, in the conventional way, causes fuel to be delivered at high pressure to the delivery chamber  48 . 
     When the swashplate  62  allows the piston  54  to move in the opposite direction to the previous one (to the left when considering FIGS. 2 and 3) under the effect of the return spring  59 , the diaphragm  30  is returned by the spring  44  to its first position in which the pumping chamber  32  has maximum volume. This, in the conventional way, causes fuel from the intake chamber  46  to be drawn into the pumping chamber  32 . 
     It will be noted that the diaphragm spring  44  allows the diaphragm  30  to return automatically to its first position, even in the absence of fuel in the main pumping unit  18 . Furthermore, when the piston  54  moves to the left when considering FIGS. 2 and 3, given the leaks of working liquid between the compression chamber  34  and the reservoir  58 , the diaphragm  30  reaches its first position before the piston  54  completes its stroke to the left. In consequence, once the diaphragm  30  has reached its first position, the pressure of the working liquid in the compression chamber  34  drops compared with that of the working liquid in the reservoir  58 , which causes the valve  76  to open and causes the compression chamber  34  to be resupplied with working liquid so as to compensate for the leakage. 
     Some simple and effective means allowing the reservoir  58  to be filled completely with working liquid will be described hereinbelow with reference in particular to FIGS. 3 and 5. 
     These filling means comprise a filling neck  80 , connected to the reservoir  58 , and which can be stoppered with a plug  82 . 
     In the example illustrated in FIGS. 3 and 5, the plug  82  is intended to collaborate with the neck  80  by screwing. The plug  82  has a more or less axial blind hole  84  communicating via a more or less radial bore  86  in the plug with a peripheral counterbore  88  of the plug extended axially by a stoppering surface  90  of this plug, which surface is intended to collaborate with a stoppering seat  92  formed in the end of the neck  80  near the reservoir  58 . 
     As a preference, the stoppering surface  90  and the stoppering seat  92  have conical overall shapes, the stoppering surface  90  converging toward the stoppering seat  92 . 
     The plug  82  can move in the neck  80 , by screwing, between a position for prestoppering the reservoir  58 , in which position the stoppering surface  90  is away from the seat  92 , above this seat  92 , as depicted in FIG. 5, and a position for stoppering this reservoir  58 , in which position the stoppering surface  90  is in sealed contact with the seat  92 , as is depicted in FIG.  3 . 
     The neck  80  is capable of containing an overflow of excess working liquid 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 prestoppering position, the peripheral counterbore  88  of this plug communicates with the reservoir  58 , so that the blind hole  84  forms a receptacle for the excess working liquid. Furthermore, when the excess is in the neck  80 , the plug  82  can be moved in this neck between its prestoppering and stoppering positions. 
     To move the plug  82 , the latter is fitted with an operating head  82 T, through which the open end of the blind hole  84  emerges. The head  82 T is delimited by a polygonal interior surface  82 I allowing the plug  82  to be turned using a conventional tool. 
     As a variant, the operating head  82 T may be delimited by a polygonal exterior surface  82 E as depicted in FIG. 6, so that the plug  82  can be turned using a conventional tool. 
     The plug  82  carries a peripheral O-ring seal  93  positioned axially between the head  82 T and the counterbore  88 . This seal  93  provides sealing between the neck  80  and the plug  82  above the counterbore  88 . 
     The plug  82  allows the reservoir  58  to be filled under vacuum as follows. 
     Initially, the plug  82  is screwed into the neck  80  into its prestoppering position as depicted in FIG.  5 . 
     In order to fill the reservoir  58  with working liquid, a vacuum is pulled in this reservoir, using conventional means, then the working liquid is introduced via the blind hole  84  of the plug. Thus, the working liquid flows into the reservoir  58  by flowing into the blind hole  84 , the radial bore  86  and the counterbore  88 . 
     The reservoir  58  continues to be filled until excess remains in the neck  80  and the blind hole  84 , as depicted in FIG.  5 . 
     Finally, with the excess present, the plug  82  is screwed into its stoppering position as depicted in FIG.  3 . The reservoir  58  is thus isolated from the filling neck  80 , the amount of working liquid remaining in the blind hole  84  being easily removed via the end of the blind hole  84  that opens through the operating head  82 T. 
     With reference to FIG. 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 diaphragm  96  separating a duct  98  that places the diaphragm  96  in communication with the working liquid of the reservoir  58  and a space  100  for disengaging the diaphragm  96 , which space is protected by a shell  102  of hemispherical overall shape. The diaphragm  96  deforms in accordance with the variations in the working liquid volume contained in the reservoir  58 . 
     FIG. 7 depicts a variant form of the plug  82 . 
     In this case, the plug  82  comprises a ball  104  which can be forced to move between a position of prestoppering the reservoir  58 , as depicted in chain line in FIG. 7, and a position of stoppering this reservoir  58 , as depicted in solid line in this FIG.  7 . 
     The surface of the ball  104  forms the stoppering surface intended to collaborate in sealed fashion with the seat  92  of the neck. 
     The filling neck  80  is stoppered using the ball  104 , as follows. 
     In the presence of excess working liquid, the level N of which is depicted in chain line in FIG. 7, the ball  104  is placed in its prestoppering position as depicted in chain line in this FIG.  7 . The ball  104  is then forced along the neck  80  so as to press it against the seat  92 , as depicted in solid line in FIG.  7 . 
     It will be noted that, during the forced movement of the ball  104  between its positions for prestoppering and stoppering the reservoir  58 , the excess working liquid, forced into the reservoir  58  under the effect of the movement of the ball  104 , is compensated for by the deformation of the diaphragm  96  of the expansion compensating means  94 , as depicted in FIG.  7 . 
     The hub  64  will be described in further detail hereinbelow with reference to FIG.  3 . 
     In the example illustrated in this FIG. 3, the hub  64  comprises a sleeve  106 , of axis coincident with the axis X, in which the swashplate  62  is housed. 
     The hub  64  also comprises a ring  108  fixed to the exterior surface of the sleeve  106 . 
     The exterior surface of the sleeve  106  forms a peripheral cylindrical surface SG for guiding the rotation of the hub in the housing body  22 . One face of the ring  108  forms a shoulder FE for the axial positioning of the hub  64  with respect to the housing body  22 . 
     Elsewhere, the housing body  22  has a liner  110 , the interior surface of which forms a cylindrical bearing surface SP in sliding contact with the peripheral guiding surface SG of the hub. 
     The housing body  22  also comprises a washer  112 , arranged at one end of the liner  110 , with one face forming a flat bearing surface FP in sliding contact with the shoulder FE of the hub. 
     The liner  110  and the washer  112  are fixed in a way known per se to the housing body  22  and are made of conventional materials, preferably ones with low coefficients of friction. 
     It will be noted that the shoulder FE of the hub  64 , extending the guiding surface SG of this hub, is urged against the bearing surface FP of the housing body  22  by the elastic return force of the pistons  54  in contact with the thrust needle bearing  60  and by the pressure of the working liquid in contact with the swashplate  62 . 
     According to a first variant depicted in FIG. 8, the cylindrical bearing surface SP is formed by the interior surface of a sleeve  114 , borne by the housing body  22 , equipped with one end extended by a flange  116  delimiting the flat bearing surface FP. 
     According to a second variant depicted in FIG. 9, the peripheral guiding surface SG of the hub is formed by the exterior surface of a sleeve  118 , in which the swashplate  62  is housed, equipped with an end extended by a flange  120  delimiting the shoulder FE for the axial positioning of the hub. The sleeve  118  of the hub collaborates with a sleeve  114  secured to the housing body  22  of the type depicted in FIG.  8 . 
     According to third and fourth variants depicted in FIGS. 10 and 11 respectively, the peripheral guide surface SG and the shoulder FE for the axial positioning of the hub are formed by the exterior surface of a stepped tubular member  122 , made of a single piece, in which the swashplate  62  is housed. The stepped member  122  may easily be manufactured in conventional ways, particularly by drawing, treating and grinding. 
     In the third variant depicted in FIG. 10, the stepped member  122  is in sliding contact with a cylindrical bearing surface SP and a flat bearing surface FP which are formed on elements similar to those depicted in FIG.  3 . 
     In the fourth variant depicted in FIG. 11, the peripheral guiding surface SG of the stepped member  122  is in contact with bearing needles  124  running more or less parallel to the axis X, and the axial positioning shoulder FE is in contact with bearing needles  126  running more or less radially with respect to the axis X . 
     The needles  124 ,  126  are contained by cages  128 ,  130  fixed, in ways known per se, to the housing body  22 . 
     The following will be noted amongst the advantages of the invention. 
     The invention makes it possible to separate the intake and delivery chambers associated with the intake and delivery valves of the high-pressure pump using simple and effective means. 
     The housing and the valve body, made of aluminum or equivalent lightweight metal, allow the pump to be lightened, without this in any way leading to problems of differential expansion between these aluminum components and other components of the pump that are made of steel or of cast iron.