GB2239297A

GB2239297A - Branch pipe couplings

Info

Publication number: GB2239297A
Application number: GB9021016A
Authority: GB
Inventors: Yoshiyuki Hashimoto
Original assignee: Usui Kokusai Sangyo Kaisha Ltd
Current assignee: Usui Kokusai Sangyo Kaisha Ltd
Priority date: 1989-09-27
Filing date: 1990-09-27
Publication date: 1991-06-26
Also published as: JPH03177694A; KR910006657A; GB9021016D0; DE4030486A1

Abstract

A branch connection for branch connectors in which surfaces of head portions 4 of branch connectors are each tightly pressed against and thus connected to the pressure bearing surfaces or head seats of a high-pressure fuel rail 1, wherein the included angles theta 1 of the pressure bearing surfaces are each larger than the included angles theta 2 of the surfaces of the head such that the outside edge portions of the head seats of a fuel rail are prevented from biting into the pressure heads. <IMAGE>

Description

f A BRANCH CONNECTION IN HIGH-PRESSURE FUEL RAIL This invention relates to

a branch connection particularly though not exclusively for connecting a branch pipe or branch piece, etc., in a fuel rail such as a high-pressure fuel manifold or a high-pressure fuel block, through which fuel is supplied to an internal combustion diesel engine under a high-pressure exceeding 1000 kgf /CM2.

Fig. 7 of the accompanying drawings shows a conventional branch connection f or branch connectors, f or example branch pipes, used in a manifold which is a conventional high-pressure fuel rail, comprising a main pipe 11 for a high-pressure fuel, straight through holes 12 orthogonal to the axis of the main pipe and branch pipes 13 each inserted into the holes and secured by welding.

Variations in the flow of fuel at an ultra-high pressure exceeding 1000kgf /CM2 repeatedly, and engine vibration etc., causes embrittlement of the welds 14, giving rise to the spraying or scattering of fuel, and sometimes leads to the separation of branch pipes 13 from the main pipe.

To solve this problem, a branch connection has been proposed in U.S Patent No. 4832376 in which a main pipe and branch pipes are mechanically connected together by a male & female type fitting. A branch connection of this type, is shown in Fig. 8, comprising a main pipe 11 with branch holes 16 having an inverted conical shape, the inner surfaces of the holes defining pressure bearing 2 surf aces or seats. Branch pipes 17 have at their ends, heads 18 of a truncated conical shape which are tightly pressed against the pressure bearing surfaces or head seats 16 optionally, with cup-shaped sealing members 19 intervening, and nuts 20 which are used for this tightening.

Such a male & female type -connection produces better sealing as compared with a connection shown in Fig. 7. As shown in Fig. 9, however, as nuts 20 are tightened, the cup-shaped sealing members 19 bite into the outside edges 21 of the pressure head seats 16 of a main pipe, pulled by connection heads 18, and deformed, thereby sometimes yielding a clearance between the sealing members and the pressure head seats. Also, as shown in Fig. 10, the heads 18 can be tipped or off set making one side bite into the outside edges 21 of a main pipe and deformed, and the other side lifts off branch holes 16, thus yielding a clearance, thereby making it impossible to obtain a proper surface contact pressure even if using the fast union of nuts 20 and screws. This is because a tightening torque is yielded by nuts 20, causing connection heads 18 to make one side bite into the outside edges 21 of a main pipe, thereby becoming unable to work as a proper axial force (thrust force) any longer.

If in this manner in Figs. 9 and 10 a clearance is produced between the sealing member 19 and the pressure head seat or between the connection head 18 and the pressure head seat, fuel may spray or scatter from this clearance, giving rise to the leakage of fuel, sometimes leading to the separation of branch 3 pipes 17 from the main pipe.

One object of this invention is to enable better sealing than was formerly available with conventional branch connections. thus preventing any deformation from occurring which is caused by the pressure surfaces of pressure head portions or the sealing members biting into the outside edges of a main pipe in the male & female type fitting connection structure.

A branch connection for a high-pressure fuel rail, comprises branch holes at intervals along the fuel rail and formed in the peripheral wall of the rail to communicate with a flow passage therein for the supply of highpressure fuel at a plurality of axially spaced positions, pressure bearing surfaces or seats which are formed as outwardly expanding in the above fuel rail such that a plurality of the branch holes can be provided each with a branch connector having a flow path which communicates with the above-mentioned flow passage, and pressure head portions formed at the above branch connectors' connection terminal portions to the above fuel rail which are pressed tightly against said pressure bearing surfaces whereby the above branch connectors are fixed to the above fuel rail; and which object is achieved by forming the above pressure bearing surfaces into the surfaces of revolution which take the axes of the above through holes as the axes of revolution, forming the above pressure head portions into the surfaces of revolution such that the above pressure head portions share a circular contact line with the above pressure bearing surfaces, thus establishing vertical 4 angles 01 of the above pressure bearing surfaces to be larger than vertical angles e2 Of the above pressure head portions.

The pressure head seat on the fuel rail is less steeply inclined than the pressure head of the branch connector so as to prevent the pressure surfaces of the head or the sealing member from biting into the pressure head seat to cause deformation.

In other words, if defining a relationship between the included angles el and e2 Of the pressure head seats and the pressure head as E), > e2, when the pressure head is pressed tightly against the pressure head seat by tightening a clamping nut on the branch connectors, the pressure surfaces are kept apart from and do not bite into the outside edge portions of the pressure head seal; and also when a cup-shaped sealing member is interposed between the pressure head seat and the pressure head, the sealing member deforms (it is squeezed inwardly from the points of contact between the sealing members and the pressure head seat) and is pressed against the pressure head such that the sealing member is prevented from biting into the outside edge portions of the pressure head seat.

Accordingly, when the branch connector is tightened by a mechanical means, the resulting thrust forces are fully transmitted to the sealing surfaces, precluding the possibility of causing the pressure head or sealing member to bite into the edge portions of the pressure head seat or producing a clearance even if pressures are increased between the pressure head and the pressure head seat and, at the same time. pressing the inner surfaces of the pressure head or the sealing member tightly against the pressure head such that airtight properties can be maintained for a long period of time and an excellent effect can be obtained enabling the connection to withstand even repeated violent and incessant variations of ultra-high fluid pressures.

Also, as a mechanical means for connecting the branch connectors to a fuel rail, this invention allows the use, for example, of a type of connection in which joint pieces are f ixed to the outside of a fuel rail so as to enclose the pressure bearing surfaces, fitting the pressure head portions on the sides of the branch connectors inside said joint pieces, allowing nuts incorporated each into the sides of the branch connectors to be tightly screwed into threaded holes in the above joint pieces.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings in which:

Figs. 1 and 2 show a first embodiment of branch connection, Fig. 1, being a longitudinal cross-section and, Fig. 2, a magnified explanatory view of the pressure bearing surface; Figs. 3 to 5 are longitudinal cross-sections of other embodiments of branch connections; Fig. 6 is a perspective view of a fuel block.

6 Figs. 7 and 8 are part cross-sectional views showing conventional branch connections; and Figs. 9 and 10 are explanatory views showing variations of conventional connection structures.

The branch connection shown in Fig. 1, includes a main pipe 1 for the f low of high-pressure fuel. It may be a fuel rail, f or example, a fuel manifold made of a metal tube with an outer diameter of 20mm and a relatively large wall thickness of 6mm. Branch holes lb are formed through the wall of the main pipe 1 to communicate with the f low passage la therein at intervals along the length of the main pipe (Fig. 1 shows the position of only one through hole 1b). Each hole lb is divergent in the radially outward direction to define a conical bearing surface or seat 2 coaxial with the hole lb; the bearing surface or seat 2 being a surface of revolution about the axis of the through hole lb. such as conicall spheroidal, ellipsoidal, paraboloidal and hyperboloidal surfaces, etc.

A joint piece 6 fitted on the main pipe 1 encloses the pressure bearing surface or seat 2. The branch connector is a branch pipe 3 through which is an axial flow path 3a, and at the end of the pipe is a pressure head 4 the pressure surface 4-1 of which is pressed against the above pressure surface or seat 2 with a cupshaped sealing member 5 intervening, and is clamped there by a nut 7 engaged in a threaded hole 6a in the joint piece 6 with a 7 washer 8 in position. The pressure head surface 4-1 is also a surface of revolution corresponding in shape to the pressure head seat 2. The cup- shaped sealing member 5 is optional.

Further, as shown in Fig. 2, the included angle 61 of the pressure head seat 2 is larger than the included angle e2 Of the pressure head 4 (01 > e2).

The difference between the included angles 01 -e2 is preferably in the range 50 to 400, since if the difference exceeds 40' the outer diameter of a pressure head surface 2 is so large as to degrade the rigidity of a main pipe 1, a large joint piece 6, etc may be required, and the pressure head seat 2 is liable to deform inwardly toward the flowpath la, while if the difference is below 5' the branch pipe 3 can easily be tipped or offset slightly to make a pressure head seat 2 receive the biting into the edge portion on the outside. The above difference in included angle is therefore preferably 15' to 25'.

The above joint piece 6 comprises a short circular ring or angular ring, and is fitted to the outside of a main pipe 1 so as to enclose the pressure head seat 2.

When connecting a branch pipe 3 to a main pipe 1, the pressure head 4 of a branch pipe 3 is inserted into the threaded hole 6a of the joint piece 6, to abut the pressure head seat 2 with a cup-shaped sealing member 5 intervening. A nut 7 threadly engaging the hole 6a is then tightened to press the head 4 8 against the seat 2.

The sealing member 5 if used, is preferably made of a rather soft metal material, such as indium, silver, copper, brass or aluminium. etc.

In the embodiment of Figure 3, the flow passage la of a main pipe 1 is of f set to the axis of the main pipe 1 to leave a thicker wall in which the branch hole 1b is formed to communicate with the flow passage la. Radially outward of the pressure head seat 2, the hole 1b is screw threaded 6a to receive the nut 7 directly. This embodiment is susceptible of compact construction and has fewer parts. Also the troublesome operation of centering the main pipe and the joint piece is avoided.

The branch connector of Figure 4 has a branch piece 51 and the main pipe is used as a fuel rail. In order to obviate the possibility that a branch pipe interferes with the outer parts as bent accompanied by a large curvature, this example was devised by taking into account such cases as when branch pieces like an elbow, etc are used or when branch pieces incorporating mechanisms like an isobaric valve, damping valve, delivery valve and discharge valve, etc are employed.

The branch connector connected to a main pipe 1 comprises of a branch piece 51. The branch piece 51 is structured such that it has a pressure head 4 with the same curvature as in the above example at one end. It is fitted tightly against the pressure 9 head seat 2 of a main pipe 1 with a sealing member 5 in position by screwing the threaded wall 21 into the threaded hole 6a in the joint piece 6. A branch pipe 31 connected to the branch piece 51 by a cap nut 23 screwed onto a sleeve in position at the other end of the branch piece. This embodiment enables a branch pipe 31 to be arranged parallel to and in the longitudinal direction of the main pipe 1.

Fig. 5 shows a branch pipe 3 which is a branch connector connected to the main pipe 1 which is a fuel rail, by means of a cap nut 24. At the centre of this cap nut 24 is an internal projection 25 in the form of a circular ring. As the screw 241 on the inner periphery of a cap nut 24 engages the screw 161 on the outer periphery of a joint piece 6 and is tightened, the projection 25 bears down via a washer 26 onto a shoulder 20a to press the press head 4 tightly against the seat 2.

Fig. 6 shows a fuel block 30 used as a fuel rail in place of the main pipe of the embodiments described above. The thick block 30 is formed with passages 31, 32 for the flow of high-pressure fuel, and has on its surface holes 33a to 33d. 34a to 34d which respectively communicate with the flow passages 31, 32. Pressure head seats as described above are formed in these holes 33a..., 34a, which are screw-tapped to receive the clamping nuts of branch connectors.

As described above, branch connections according to the present invention completely prevent the pressure surfaces or the sealing members placed between the pressure head and the pressure head seats f rom biting into outside edge portions of a main pipe because the pressure head seats on the fuel rail are less steeply inclined than the pressure heads on the branch connectors. As a result. deformation of the pressure surfaces or the sealing members is prevented and the surface contact pressure can be increased to completely eliminate any clearance, and hence leakage of a fluid, and also greatly upgrade the durability of the sealing members themselves.

Accordingly, the sealing performance is preserved even when exposed to repeated application of an ultra-high fluid pressure under incessant vibrations, and a proper connection is maintained for a long period of time. This invention, therefore, provides a highly safe and reliable structure as the connection structure for branch connectors used in a high-pressure fuel rail.

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Claims

1. A branch connection between a conduit defining a main fluid flowpath and a branch connector having a flow path in communication with the main f lowpath, wherein a pressure head of a branch connector is held against a pressure head seat formed in a branch hole in the conduit wall. the pressure head seat comprising a surface of revolution about the axis of the branch hole and the included angle of the pressure head seat being larger than the included angle of the pressure head.

2. A branch connection for a high-pressure fuel rail or conduit in which branch holes are formed at a plurality of positions in the peripheral wall of a conduit defining a flow passage for the supply of high-pressure fuel, each connection comprising a branch connector having a pressure head held tightly against a pressure head seat formed in the branch hole and being divergent outwardly toward the exterior of the fuel rail or conduit, the pressure head seat comprising a surface of revolution about the axis of the branch hole. the pressure head portions sharing contact lines with the pressure bearing surfaces being formed each into surfaces of revolution, and the included angle of the pressure head seat being larger than the included angle of the pressure head.

3. A connection according to claim 1 or claim 2 wherein a difference between the included angles is 50 to 400.

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4. A connection according to any preceding claim wherein the branch connector is connected to the f uel rail or conduit by clamping means in screw threaded engagement with branch connectors or the threaded walls provided on said branch connectors each with a threaded hole in the fuel rail or conduit or in a joint piece fitted around the fuel rail.

5. A connection according to any preceding claim. wherein the pressure head seat comprises a conical surface and the pressure head on the connector has a truncated conical surface.

6. A connection according to any preceding claim. wherein the branch connector comprises a branch pipe or branch piece.

7. A connection according to any preceding claim. wherein the fuel rail or conduit comprises a fuel manifold or a fuel block.

8. A branch connection constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 6 of the accompanying drawings.

Published 1991 at Ihe Patent Office. State House. 66171 High Holborn. London WC1R47P. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point Cwmfelinrach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray. Kent.