(19)
(11)EP 0 117 218 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
23.11.1988 Bulletin 1988/47

(21)Application number: 84630019.2

(22)Date of filing:  15.02.1984
(51)International Patent Classification (IPC)4F02M 59/44, F02M 59/48

(54)

Mounting arrangement for injection barrel in housing of fuel injection pump

Einbauanordnung für Einspritzzylinder im Gehäuse einer Einspritzpumpe

Disposition de montage pour cylindre d'injection dans la boîte d'une pompe d'injection


(84)Designated Contracting States:
AT DE FR GB IT NL SE

(30)Priority: 17.02.1983 US 467558

(43)Date of publication of application:
29.08.1984 Bulletin 1984/35

(73)Proprietor: AIL CORPORATION
Columbia South Carolina 29203 (US)

(72)Inventors:
  • Kimberley, John Arthur
    East Granby Connecticut 06026 (US)
  • Cavanaugh, John Bernard
    West Springfield Massachusetts 01089 (US)

(74)Representative: Weydert, Robert et al
Dennemeyer & Associates Sàrl P.O. Box 1502
1015 Luxembourg
1015 Luxembourg (LU)


(56)References cited: : 
AT-B- 291 679
US-A- 3 885 895
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The present invention relates to an injection pump assembly and more particularly to an improved arrangement for mounting one or more injection barrels in respective bores formed in the housing of a diesel injection pump.

    [0002] In diesel fuel injection pumps, and particularly in so-called in-line injection pumps in which a plurality of discrete pumping units are serially arranged in a pump housing, it is common to mount each unit pump within a respective bore formed in the pump housing. Typically, each such unit pump contained within the total pump housing includes a respective injection barrel which in turn contains a pumping plunger operating in one end thereof and an outlet valve assembly controll- ably closing the outlet end thereof. Such pumping unit is mounted in a respective bore in the pump housing such that the pumping plunger may be actuated by a cam and otherwise controlled by a fuel rack, both of which are also housed within the fuel pump housing and serve to control the other pumping units also.

    [0003] In some such fuel injection pumps, the injection barrel of the unit pump is fitted into the respective bore formed in the pump housing in a manner such that by axially loading the barrel, a metal-to- metal seal between the barrel and housing is provided to prevent the fuel within the unit pump from leaking beyond the bore in the pump housing either to the outside environment or to the crankshaft region of the pump at which it may adversely interact with the pump lubricants and thereby increase bearing wear. Such mounting arrangement of injection barrels within respective bores in the pump housing may be objectionable however because of the considerable axial compressive forces acting on the injection barrel. These forces may be further aggravated by thermal changes in the pump and may distort the injection barrels sufficiently to interfere with the operation and/or life of the pumping plunger housed therein.

    [0004] At least in part to avoid the aforementioned problem, many injection pumps mount, or more specifically suspend, the injection barrel within the pump housing bore such that the compressive forces on the barrel are substantially reduced. More specifically, the outside diameter of the injection barrel is typically somewhat smaller than that of the diameter of the bore within the pump housing into which it is to be inserted, and the lower end of the barrel is not axially loaded into sealing engagement with the housing. Then however is becomes necessary to provide additional seals for preventing the aforementioned objectionable leakage of fuel from the unit pump. Typically, a pair of resilient annular seals are positioned about a fuel injection barrel such that they provide a seal between it and the wall of the housing bore. The annular seals are axially spaced such that the portion of the injection barrel from which fuel might leak is contained therebetween. US-A-3,885,895 and US-A-4,060,350 illustrate one such sealing arrangement in which the annular seals are housed in respective seats formed in the wall of the housing bore. That arrangement may be objectionable however because it requires each seal seat to be performed by a trepanning operation. Moreover, relatively sharp-edged shoulders formed on the outer perimeter of the injection barrel may shave or scrape the annular seals during insertion of the barrel, thereby diminishing their effectiveness as seals.

    [0005] In certain other pumps, the seat for the annular seals is formed in the external surface of the injection barrel and is more easily accomplished than the aforementioned trepanning operation required for forming the seal seats within the wall of the housing bore. However, this arrangement is also less than optimum because the geometry of the housing bore has included one, and typically several, edges against which the annular seals rub during insertion or removal of the injection barrel respectively into or out of the housing bore. These edges typically include small burrs as a result of machining and are located such that deburring may be difficult or impossible. Thus, the annular seals in this arrangement may also become shaved and their effectiveness as seals impaired.

    [0006] An injection pump according to the precharacterizing portion of claim 1 with the seats for the annular seals formed in the external surface of the injection barrel is disclosed in AT-B-291 679. In the mounted position of the injection barrel of AT-B-291 679 the annular seals are in engagement with cylindrical surface portions of the wall of the mounting bore. Small chamfered surface portions lead toward these cylindrical surface portions. While these chamfered surface portions facilitate insertion _of the injection barrel, they cannot, however, avoid or eliminate shaving of the annular seals during insertion of the injection barrel.

    [0007] Accordingly, it is the object of the present invention to provide an improved arrangement for the mounting of pump injection barrels within the respective bores formed in a fuel injection pump housing which minimizes or eliminates in a cost effective manner the wear and destruction of annular seals interposed between a respective fuel injection barrel and housing bore.

    [0008] In accordance with the invention this is achieved by the features claimed in the characterizing portion of claim 1.

    [0009] There is provided an improved arrangement for mounting an injection barrel within the bore of a fuel injection pump housing and for maintaining the integrity of a fluid seal therebetween. In an injection pump assembly there is provided a pump housing having one and typically several, mounting bores extending thereinto from a surface thereof, and a respective injection barrel located at a mounted position in each of the mounting bores for housing a respective pumping piston in one end thereof and a respective valve in the other end. A pumping chamber is defined within each injection barrel between the respective pumping piston and valve. Each injection barrel includes at least one annular seat formed in the external periphery thereof, and a respective annular seal is contained in the seat. As used herein with reference to the seals and their seats, "annular" typically refers to an O-ring, but may also include rectangular or similar closed- loop geometries, as viewed along the axis. The annular seal, when uncompressed, normally projects radially outward beyond the external periphery of the injection barrel axially adjacent to the seals seat.

    [0010] The annular seal is radially compressed by radial engagement with the wall of the mounting bore in the pump housing when the injection barrel is in its mounted position in the bore. Each such mounting bore in the pump housing is chamfered to a diameter which is sufficiently small for the compressive engagement with the 0-ring seal when the injection barrel is at its mounted position. Moreover, the diameter of the mounting bore between the surface of the pump housing and that chamfer is always greaterthan the diameter of the annular seal when uncompressed so as to prevent shaving the annular seal during axial displacement of the injection barrel into and out of its mounted position.

    [0011] At least two axially-spaced annular seals may be seated on the injection barrel, and the mounting bore in the pump housing may be provided with a respective pair of separate chamfered surfaces for engagement with the respective seals. To obtain the benefits of the invention, the axially outermost annular seal will be seated in a portion of the injection barrel having a first outside diameter and the second and any subsequent annular seals axially inward therefrom will be arranged about portions of the injection barrel having successively smaller outside diameters. Correspondingly, the diameter of the mounting bore in the pump housing decreases in steps between successive chamfers moving axially into the pump housing from the surface thereof.

    [0012] The chamfers in each of the mounting bores in the pump housing are preferably formed at a relatively shallow angle to the bore axis to permit some axial adjustment of the final positioning of the injection barrel within the bore, yet insuring a sufficient seal between the housing and injection barrel via the 0-ring seal. Preferably all of the chamfers in a mounting bore are formed at the same angle, that angle typically being less than 20°, i.e., about 14° included.

    [0013] An embodiment of the injection pump will now be described with reference to the drawings, wherein:

    Fig. 1 is a perspective view of an in-line fuel injection pump, partly broken away to reveal a unit pump mounted within a bore formed in the housing of the fuel injection pump;

    Fig. 2 is an enlarged front sectional view of a portion of the pump of Fig. 1 taken along lines 2-2 thereof, illustrating a fuel injection barrel and 0- ring seals mounted in a pump housing bore; and

    Fig. 3 is a view similar to that of Fig. 2, but having the fuel injection barrel removed to reveal the details of the mounting bore.



    [0014] Referring to Fig. 1, there is illustrated an in-line fuel injection pump, generally designated 10, for developing and delivering pressurized pulses of fuel to an internal combustion engine, such as a diesel. Fuel injection pump 10 includes a cast housing 12 into which are formed a series of mounting bores 14, only one of which being shown in Fig. 1. The mounting bores 14 are substantially vertically oriented, are parallel to one another and are arranged in in-line relationship. The bottom ends of the mounting bores 14 open into a front-to-rear extending cavity in which is mounted a cam shaft 16. The cam shaft 16 includes a respective cam 17 associated with each of the bores 14.

    [0015] A so-called unit pump 18 is mounted in each of the housing bores 14. Each unit pump 18 includes a substantially cylindrical injection barrel 20 having a pumping piston 22 disposed for reciprocation in its lower or axially inner end and having an outletvalve assembly 24 installed in its upper or axially outer end. A pumping chamber 26 is defined within the injection barrel 20 between the pumping piston 22 and the outlet valve assembly 24. A compression spring 28 biases the pumping piston 22 downward into engagement with a cam follower 30 such that the axial displacement of the pumping piston 22 is controlled by the respective cam 17 associated therewith. The injection barrel 20 of each unit pump 18 includes a head flange portion 31 extending transversely thereof at its axially outer end. Each flange includes a pair of axial bores or slots 32 for registry with a corresponding pair of threaded openings 33 tapped into the upper surface of the pump housing 12 on either side of a mounting bore 14. Corresponding pairs of stud bolts 34 are threaded into the housing openings 33 such that their upper ends may extend upwardly through the respective bores or slots 32 in the head flange 31 of a respective injection barrel 20. Respective nuts 36 then threadedly engage the upper ends of the stud bolts 34 to maintain the injection barrel 20, and thus the unit pump 18, in a mounted position within the bore 14 of pump housing 12.

    [0016] The pump housing 12 is provided with a fuel gallery 38 containing fuel at a relatively low pressure for supply to the pump chamber 26. The control ports 40 through the wall of the injection barrel 20 provide communication between the pump chamber 26 and the fuel gallery 38. The unit pump 18 operates in a well known manner by admitting fuel to the pump chamber 26 through port 40 during the down stroke of pumping piston 22. Upon the upward stroke of the pumping piston 22, the ports 40 are closed and the fuel in pump chamber 26 is pressurized to a high pressure whereupon it is ejected through outlet valve assembly 24 for delivery via a fuel line to a fuel injector associated with the internal combustion engine. The high pressure within the pumping chamber 26 terminates when the pumping piston 22 is displaced upwardly to a position at which the upper edges of a pair of helical relief slots 48 disposed on the outer periphery of the pumping piston come into registry with the ports 40. A central bore (shown in dotted line) in the upper end of pumping piston 22 includes a radially extending lower arm which communicates with the relief slots 48 to provide the requisite relief path from the pumping chamber 26 through the piston 22 and to the ports 40. The outer periphery of the injection barrel 20 may be somewhat reduced in the region of the ports 40 to allow the positioning thereover of a baffle sleeve 42 which includes relief ports 45 for preserving communication with the fuel gallery 38. The baffle sleeve 42 may be held in position by a snap ring 44 and serves to absorb the impact energy of the fuel pulse which is emitted at the end of the fuel delivery with high energy through the control port 40.

    [0017] The injection barrel 20 includes an upper annular seat 50 in its external surface and a lower annular seat 52 also in its external surface. Annular seals 59 and 56 of a suitable resilient material are positioned in the seats 50, 52 respectively. The annular seal 59 is positioned axially above the pumping chamber 26 and the annular seal 56 is positioned axially below that pumping chamber from preventing leakage of the fuel beyond the region of the fuel gallery 38. In the region of the upper annular seal 59, the outside diameter of the fuel injection barrel 20 is somewhat greater than it is in the region containing the lower annular seal 56. Correspondingly, the outside diameter of the annular seal 59 in its uncompressed state is somewhat greater than that of the annular seal 56 in its uncompressed state.

    [0018] Referring to the mounting bore 14 in pump housing 12, it is generally formed during the casting operation, with much of the wall surface being finished by a machining operation. While the lowermost portions of the mounting bore 14 which housed the cam follower 30 may be machined by bottom entry into the housing 12, that portion of the mounting bore housing most of the injection barrel 20 extends downwardly from the uppermost surface of the pump housing 12 and is machined from that upper surface. The mounting bore 14 of the present embodiment includes a respective chamfered surface for engaging each of the annular seals 56,59 to effect the requisite fluid seal. More specifically, an axially inner, or lower, chamfer 66 is provided for engagement with lower annular seal 56, and an axially outer, or upper, chamfer 69 is provided for engagement with the upper annular seal 59. Both chamfers 66 and 69 are preferably of the same included angle a, and that angle is relatively small. For instance, the included angle a of chamfer 66 and 69 relative to the axis of bore 14 is less than about 20°, being about 14° in the illustrated embodiment.

    [0019] Referring to Figs. 2 and 3, it is known in the type of injection pump employing a suspended injection barrel to provide for adjusting the axial positioning of the barrel, as by shims 70a and 70b between the pump housing 12 and the injection barrel head flange 31. Such axial adjustment of the mounted position of injection barrel 20 serves in a known manner to adjust the instant or timing at which the pumping piston 22 closes port 40 and thus begins the pressurized fuel pulse which is delivered to the engine. Thus by adjusting the actual or effective thickness of shims 70a, 70b, the mounted position of barrel 20 can be adjusted axially within a range, that range being represented by the bracketed zones 166 and 169 associated with the respective chamfers 66 and 69 or bore 14 which represent the respective regions of sealing engagement of the annular seals 56 and 59 with the housing 12. The included angle of the chamfers 66 and 69 is selected so as to maintain the fluid seal between the annular seals 56,59 and the chamfers 66 and 69 throughout the full range of axial adjustment. It will be noted that the upper and lower ends or shoulders 69a and 69b of chamfer 69, and the upper and lower ends or shoulders 66a and 66b of chamfer 66 are respectively beyond the axially upper and lower bounds of the zones 169 and 166 respectively such that the respective annular seals 59 and 56 are only positioned on the respective smooth chamfered surfaces in any permissible mounted position of the injection barrel. Accordingly, the chamfered surfaces 66 and 69 extend over an axial portion of the mounting bore 14 of sufficient length to provide engagement of said annular seals 56 and 59 with the chamfered surfaces 66 and 69 when the injection barrel 20 is at said mounted position.

    [0020] Consistent with the aforementioned constraints, and to insure that the annular seals 59 and 56 are not shaved by contacting any shoulder or edge surface in bore 14 during insertion, axial adjustment or withdrawal of injection barrel 20, the diameter of bore 14 at lower end or shoulder 66b of chamfer 66 is less than that required for maximum radial compression of the annular seal 56 and the diameter at the upper end or shoulder 66a of that chamfer is greater than the uncompressed diameter of that annular seal. Similar geometrical constraints exist regarding the diameters of chamfer ends of shoulders 69b and 69a relative to annular seal 59. Importantly, it should also be noted that nowhere axially above chamfer 66 in bore 14 is the diameter of that bore as small as the outside diameter of lower annular seal 56 in its uncompressed state. A similar limitation applies to the region of bore 14 above chamfer 69 relative to the uncompressed outside diameter of annular seal 59, however in the illustrated embodiment that limitation is readily met by beginning the upper end 69a of that chamfer at the upper surface of the pump housing 12.

    [0021] Thus there has been described an improved arrangement for mounting an injection barrel within the bore of a fueling pump and for minimizing or eliminating the deterioration of the annular seals, as by being shaved on sharp edges.

    [0022] Reference is made to EP-A-0117219 (priority date 17.2.83) which describes a similar pump however deals with shims at the head flange of the injection barrel.


    Claims

    1. Injection pump assembly for an internal combustion engine, said assembly including a pump housing (12) having at least one mounting bore (14) extending thereinto from a mounting surface thereof, and a respective injection barrel (20), located at a mounted position in each said mounting bore (14) for housing a respective pumping piston (22) in one end thereof and a respective valve means (24) in the other end thereof, each said injection barrel (20) including at least one annular seat (50, 52) formed in an external surface thereof and a respective annular seal (59, 56) in said seat (50, 52), said annular seal (59, 56) normally projecting radially outward beyond the external surface of the injection barrel (20) when uncompressed, said annular seal (59, 56) being radially compressed by radial engagement with the wall of said mounting bore (14) when said injection barrel is in said mounted position in said bore (14) to provide a fluid seal therebetween, said mounting bore (14) having at least one chamfered surface (66, 69) formed in the wall thereof, said chamfered surface having a large diameter end (66a, 69a) towards the mounting surface and a small diameter end (66b, 69b) remote from the mounting surface and the large diameter end (66a, 69a) of the chamfered surface (66, 69) being larger than the uncompressed diameter of said annular seal (56, 59), whereby the diameter of the mounting bore (14) opening from the mounting surface into said chamfered surface (66, 69) is always greater than the diameter of said annular seal (56, 59),
    characterized in that the chamfered surface (66, 69) extends over an axial portion of the mounting bore (14) of sufficient length to provide engagement of said annular seal (56, 59) with the chamfered surface when said injection barrel (20) is at said mounted position, that the small diameter end (66b, 69b) of said chamfered surface (66, 69) is less than that required for maximum radial compression of said annular seal (56, 59), and that the included angle of said chamfered surface (66, 69) is selected to allow axial adjustment of said mounted position of the injection barrel (20) while maintaining said fluid seal.
     
    2. Pump assembly according to claim 1, characterized in that said injection barrel (20) includes a first outside diameter along a first portion thereof and a second outside diameter less than said first diameter along a second portion thereof axially inward from said first portion, first and second said annular seals (56, 59) being seated in respective first and second said seats (50, 52) in said first and second portions of said barrel (20) respectively, and that said bore (14) includes first and second said chamfered surfaces (66, 69) for engagement with said first and second seals (56, 59) respectively when said injection barrel (20) is in its said mounted position.
     
    3. Pump assembly according to claim 2, characterized in that a pumping chamber (26) is defined within said injection barrel (20) axially between said pumping piston (22) and said valve means (24) and that said first and said second annular seals (56, 59) are respectively positioned axially beyond the respective opposite ends of said pumping chamber (26).
     
    4. Pump assembly according to anyone of claims 1 to 3, characterized in that the included angles of said first and said second chamfered surfaces (66, 69) are substantially the same and are less than about 20°.
     
    5. Pump assembly according to anyone of claims 1 to 4, characterized in that said injection barrel (20) includes a head flange (31) affixed thereto and further including clamping means (34, 36) cooperating with said head flange (31) and said pump housing (12) for maintaining said injection barrel (20) in said mounted position.
     


    Ansprüche

    1. Einspritzpumpenbaugruppe für einen Verbrennungsmotor, wobei die Baugruppe ein Pumpengehäuse (12) aufweist, das wenigstens eine Befestigungsbohrung (14) hat, die sich von einer Befestigungsfläche desselben aus in dasselbe erstreckt, und einen Einspritzzylinder (20), der in einer befestigten Position in jeder Befestigungsbohrung (14) angeordnet ist, zum Aufnehmen eines Pumpkolbens (22) in einem Ende desselben und einer Ventileinrichtung (24) in dem anderen Ende desselben, wobei jeder Einspritzzylinder (20) wenigstens einen ringförmigen Sitz (50, 52) aufweist, der in einer äußeren Oberfläche desselben gebildet ist, und eine Ringdichtung (59, 56) in dem Sitz (50, 52), wobei die Ringdichtung (59, 56) normalerweise über die äußere Oberfläche des Einspritzzylinders (20) hinaus radial nach außen vorsteht, wenn sie nicht zusammengedrückt ist, wobei die Ringdichtung (59, 56) durch radiale Anlage an der Wand der Befestigungsbohrung (14) radial zusammengedrückt wird, wenn der Einspritzzylinder in der befestigten Position in der Bohrung (14) ist, um eine Fluidabdichtung zwischen denselben herzustellen, wobei die Befestigungsbohrung (14) wenigstens eine kegelige Oberfläche (66, 69) hat, die in deren Wand gebildet ist, wobei die kegelige Oberfläche wenigstens ein Ende (66a, 69a) großen Durchmessers zu der Befestigungsfläche hin und ein Ende (66b, 69b) kleinen Durchmessers entfernt von der Befestigungsfläche hat und wobei das Ende (66a, 69a) großen Durchmessers der kegeligen Oberfläche (66, 69) größer als der nicht zusammengedrückte Durchmesser der Ringdichtung (56, 59) ist, wodurch der Durchmesser der Befestigungsbohrung (14), die von der Befestigungsfläche her in die kegelige Oberfläche (66, 69) mündet, immer größer ist als der Durchmesser der Ringdichtung (56, 59),.
    dadurch gekennzeichnet, daß sich die kegelige Oberfläche (66, 69) über einen axialen Teil der Befestigungsbohrung (14) mit ausreichender Länge erstreckt, um für die Berührung der Ringdichtung (56, 59) mit der kegeligen Oberfläche zu sorgen, wenn der Einspritzzylinder (20) in der befestigten Position ist, daß das Ende (66b, 69b) kleinen Durchmessers der kegeligen Oberfläche (66, 69) kleiner als das ist, das zur maximalen radialen Zusammendrükkung der Ringdichtung (56, 59) erforderlich ist, und daß der eingeschlossene Winkel der kegeligen Oberfläche (66, 69) so gewählt ist, daß er das axiale Einstellen des befestigten Teils des Einspritzzylinders (20) gestattet und dabei die Fluidabdichtung aufrechterhält.
     
    2. Pumpenbaugruppe nach Anspruch 1, dadurch gekennzeichnet, daß der Einspritzzylinder (20) einen ersten äußeren Durchmesser längs eines ersten Teils desselben und einen zweiten äußeren Durchmesser, der kleiner als der erste Durchmesser ist, längs eines zweiten Teils desselben aufweist, welcher sich axial einwärts von dem ersten Teil befindet, eine erste und eine zweite Ringdichtung (56, 59), die in einem ersten bzw. zweiten Sitz (50, 52) in dem ersten bzw. zweiten Teil des Zylinders (20) sitzen, und daß die Bohrung (14) eine erste und eine zweiten kegelige Oberfläche (66, 69) zum Erfassen der ersten bzw. zweiten Dichtung (56, 59), wenn der Einspritzzylinder (20) in seiner befestigten Position ist, aufweist.
     
    3. Pumpenbaugruppe nach Anspruch 2, dadurch gekennzeichnet, daß eine Pumpkammer (26) in dem Einspritzzylinder (20) axial zwischen dem Pumpkolben (22) und der Ventileinrichtung (24) gebildet ist und daß die erste und die zweite Ringdichtung (56, 59) axial jenseits der entgegengesetzen Enden der Pumpkammer (26) angeordnet sind.
     
    4. Pumpenbaugruppe nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die eingeschlossenen Winkel der ersten und der zweiten kegeligen Oberfläche (66, 69) im wesentlichen dieselben und kleiner als etwa 20° sind.
     
    5. Pumpenbaugruppe nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der Einspritzzylinder (20) einen Kopfflansch (31) aufweist, der an ihm befestigt ist, und eine Klemmeinrichtung (34, 36), die mit dem Kopfflansch (31) und dem Pumpengehäuse (12) zusammenwirkt, um den Einspritzzylinder (20) in der befestigten Position zu halten.
     


    Revendications

    1. Ensemble de pompe à injection pour moteur à combustion interne, cet ensemble comprenant un carter de pompe (12) dans lequel au moins un alésage de montage (14) s'étend à partir d'une surface de montage de ce carter, et un cylindre d'injection (20) respectif, placé en une position montée dans l'alésage de montage (14) associé et servant à loger un piston de pompage (22) respectif dans l'une de ses extrémités et un dispositif à clapet (24) respectif dans son autre extrémité, chaque cylindre d'injection (20) comportant au moins un siège annulaire (50, 52) ménagé dans une surface extérieure de ce cylindre et un joint annulaire d'étanchéité (56, 59) respectif placé dans ce siège (50, 52), ce joint annulaire d'étanchéité (56, 59) faisant normalement saillie radialement vers l'extérieur, au delà de la surface extérieure du cylindre d'injection (20), lorsqu'il est à l'état non comprimé, ce joint annulaire d'étanchéité (56, 59) se trouvant comprimé radialement du fait de son contact radial avec la paroi de l'alésage de montage (14) lorsque le cylindre d'injection (20) est dans ladite position montée dans cet alésage (14), de façon à assurer entre eux une étanchéité aux fluides, l'alésage-de montage (14) comportant au moins une surface chanfreinée (66, 69) réalisée dans sa paroi, cette surface chanfreinée (66, 69) offrant une extrémité de grand diamètre (66a, 69a) vers la surface de montage et une extrémité de petit diamètre (66b, 69b) à l'opposé de cette surface de montage et l'extrémité de grand diamètre (66a, 69a) de la surface chanfreinée (66, 69) étant plus grande que le diamètre non comprimé du joint annulaire d'étanchéité (56, 59), tandis que le diamètre de l'alésage de montage (14) constituant le débouché de la surface chanfreinée (66, 69) du côté de la surface de montage est toujours supérieur au diamètre du joint annulaire d'étanchéité (56, 59),
    caractérisé en ce que la surface chanfreinée (66, 69) s'étend sur une partie axiale de l'alésage de montage (14) qui est d'une longueur suffisante pour assurer un contact du joint annulaire d'étanchéité (56, 59) avec la surface chanfreinée lorsque le cylindre d'injection (20) est dans ladite position montée, en ce que l'extrémité de petit diamètre (66b, 69b) de la surface chanfreinée (66, 69) est inférieure à celle nécessaire pour une compression radiale maximale du joint annulaire d'étanchéité (56, 59), et en ce que l'angle d'ouverture de la surface chanfreinée (66, 69) est choisi de façon à permettre un ajustement axial de la position montée du cylindre d'injection (20), tout en maintenant une étanchéité aux fluides.
     
    2. Ensemble de pompe suivant la revendication 1, caractérisé en ce que le cylindre d'injection (20) offre un premier diamètre extérieur le long d'une première partie de ce cylindre et un second diamètre extérieur, inférieur au premier diamètre, le long d'une seconde partie de ce cylindre qui est située axialement vers l'intérieur par rapport à la première partie, un premier et un second joints annulaires d'étanchéité (56, 59) qui sont placés dans un premier et un second sièges respectifs (50, 52) ménagés respectivement dans la première et la seconde parties du cylindre (20), et en ce que l'alésage (14) présente une première et une seconde desdites surfaces chanfreinées (66, 69) destinées à être au contact respectivement du premier et du second joints annulaires d'étanchéité (56, 59) lorsque le cylindre d'injection (20) est dans sa dite position montée.
     
    3. Ensemble de pompe suivant la revendication 2, caractérisé en ce qu'une chambre de pompage (26) est délimitée à l'intérieur du cylindre d'injection (20), dans une position axiale située entre le piston de pompage (22) et le dispositif à clapet (24), et en ce que le premier et le second joints annulaires d'étanchéité (56, 59) sont respectivement disposés au delà, dans le sens axiale, des extrémités opposées respectives de cette chambre de pompage (26).
     
    4. Ensemble de pompe suivant l'une quelconque des revendications 1 à 3, caractérisé en ce que les angles d'ouverture de la première et de la seconde surfaces chanfreinées (66, 69) sont sensiblement égaux et sont inférieurs à environ 20°.
     
    5. Ensemble de pompe suivant l'une quelconque des revendications 1 à 4, caractérisé en ce que le cylindre d'injection (20) comporte une bride de tête (31) qui en est solidaire et comporte en outre des moyens de serrage (34, 36) coopérant avec cette bride de tête (31) et le carter de pompe (12) en vue de maintenir le cylindre d'injection (20) dans ladite position montée.
     




    Drawing