GB2274886A

GB2274886A - Fuel injection pump delivery valve.

Info

Publication number: GB2274886A
Application number: GB9401027A
Authority: GB
Inventors: Hanspeter Mayer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-01-21
Filing date: 1994-01-20
Publication date: 1994-08-10
Anticipated expiration: 2014-01-20
Also published as: GB2274886B; GB9401027D0; JPH06241140A; DE4301521A1

Description

2274886

DESCRIPTION "DELIVERY VALVES"

The invention relates to delivery valves.

A delivery valve known from DE-OS 34 17 210 Alt is disposed in a delivery line between a pump working chamber and a fuel-injection point. A valve body is installed from the outside into the pump housing and is clamped in the pump housing by means of an installation bolt which is screwed into the pump housing, for which purpose an end face of the installation bolt, which is in addition formed as a connecting-piece for a fuel- injection line to the fuel-injection point, lies in a sealing manner against an annular shoulder of the valve body, which end face protrudes into the pump housing, and thus presses the valve body with its end face against a step of a receiving bore in the pump housing. The valve body comprises, in a known manner, an axial through bore, in which a valve member is guided which opens in the direction towards the fuel-injection line against the force of a valve spring, wherein the end face of the valve body remote from the step is formed as a valve seat, with which valve seat a sealing surface at the valve member cooperates. Inside the valve member a non-return valve is installed working in opposition to the opening direction of the valve member. This non- return valve. in the opened state, opens a duct which connects a chamber of the valve member facing the fuel-injection line, to a chamber of the valve member facing the pump working chamber, and therefore, when the valve member is in position at the valve seat, renders possible a reduction of pressure in the fuelinjection line to a predetermined adjustable value.

The known delivery valve therefore has the disadvantage that the delivery valve consisting of individual component parts causes high manufacturing costs during its incorporation into the housing of the fuel-injection pump. Moreover a narrow fit is required between the valve body and the delivery valve holder, as well as between the valve body and the pump housing in order to accommodate the pressure forces inside the valve, which results in high production and installation costs with regard to the tolerances, since these wall surfaces also serve as sealing surfaces by means of which a reliable sealing from the outside must be achieved when there are high working pressures in the high-pressure part, wherein a high contact force must be used in order to obtain the required sealing tightness.

At high fuel-injection pressures of up to 1500 bar, necessary for an optimal mixture preparation and combustion in modern internal combustion engines, sealing problems arise in the known delivery valve so that the preparation and combustion are no longer entirely sufficient for very high fuel-injection pressures.

In accordance with the present invention there is provided a delivery valve for installation in a delivery line between a pump working chamber of a fuel-injection pump and an injection point at the internal combustion engine to be supplied from this injection point, comprising a delivery valve holder having a connecting sleeve and a through duct, a valve body having a valve seat. which is clamped to the delivery valve holder and through which said through duct also extends and having a delivery valve closure member, which is disposed between the said valve seat and a compression spring, supported in a valve chamber formed from a widening in the cross-sectional area of the through duct of the delivery valve holder, the delivery valve closure member having a sealing surface which cooperates with said valve seat, wherein the delivery valve holder is screwed to the valve body in a sealing manner and, with this valve body and the delivery valve member disposed between them, forms a preassembled delivery-valve and holder assembly. which assembly is installable and clampable in a guide bore of a pump housing, for which purpose the delivery valve holder has a shoulder at a transition from the connecting sleeve to a larger diameter part of the delivery valve holder, which, larger diameter part receives the valve chamber, and with which shoulder the delivery valve holder can be brought into position in a sealing manner at an annular step of a bore connected to the pump working chamber at the transition of this bore to the guide bore, and wherein the connecting sleeve protrudes out of the pump housing through the guide bore, and is clamped at this point to the pump housing into a sealing position of the shoulder and is connectable to the delivery line.

This has the advantage that. because the delivery valve is a preassembled delivery-valve and holder assembly, the installation into the housing of the fuel-injection pump is greatly simplified. The pressure-equalising valve unit can therefore be preset prior to its installation into a blind bore and be checked for sealing tightness.

Preferably, a biting edge is provided at the annular shoulder of the delivery valve holder, which biting edge acts as a sealing edge with the annular step of the pump housing, to achieve a reliable sealing from the outside even when there are high pump pressures, wherein the tolerances of the delivery valve holder and of the guide bore in the pump -5housing, which receives this holder, must therefore assure an unhindered installation of the delivery valve holder into the guide bore of the pump housing, and are therefore convenient to produce from a production engineering point of view. In addition the biting edge working axially to the delivery valve has the advantage that the pressure of the fuel supports the sealing effect at the biting edge so that in contrast to the known delivery valve, when the pressure is increased, the sealing effect likewise increases.

Moreover the valve, which is subjected to the high pressure on almost every side, is subjected to only slight deforming forces.

The sealing of the delivery valve holder with regard to the valve body is achieved likewise by means of an annular biting edge, coaxial to the valve axis, disposed at the valve body, which biting edge cooperates with the end face of the delivery valve holder and the sealing effect of which biting edge likewise increases when the pressure rises, as described, wherein a reverse arrangement of the biting edge at the end face of the delivery valve holder is possible.

By means of the end of the delivery valve holder, protruding out of the pump housing, it is also possible to clamp the preassembled delivery-valve and holder assembly from the outside against the pump housing, wherein this can, in an advantageous manner, be achieved, by means of a thread disposed at the delivery valve holder, directly into an inner thread of the wall of the guide bore as well as by means of a screwed-in nut.

By way of example only specific embodiments of the invention will now be described, with reference to the accompanying drawings, in which:- Figure 1 is a longitudinal sectional view through a first embodiment of a delivery valve formed as a pressure-equalising valve, the delivery valve holder of which forms, with the valve body, a delivery-valve and holder assembly, which assembly is sealed at the pump housing by means of a biting edge, and which assembly is clamped against the pump housing by means of a screwed-in nut; Figure 2 illustrates a second embodiment analogous to Figure 1, having a multi-part valve body; and Figure 3 is a longitudinal sectional view through a third embodiment in which the delivery valve holder is divided into a connecting sleeve and a threaded bushing.

In the first embodiment, illustrated in Figure 1, a delivery valve 1 is installed into a stepped guide bore 3 of a housing 5 of a fuel-injection pump. The guide bore 3 forms a part of a fuel high-pressure line, not illustrated in more detail, between a pump working chamber of the fuelinjection pump and an injection point in the combustion chamber of the internal combustion engine to be supplied. The larger diameter bore part of the stepped guide bore faces the pump working chamber, and preferably lies closely adjacent thereto.

In addition a tubular delivery valve holder 7 is installed into the stepped guide bore 3 in such a way that the delivery valve holder 7 lies with an annular shoulder 9, produced by a narrowing in diameter, against an annular step 11 of the stepped guide bore 3, wherein its reduced diameter part forms a connecting sleeve 13 receiving an injection line to the injection point, which connecting sleeve partly protrudes out of the pump housing 5. The delivery valve holder 7 comprises on its inside an axial stepped through bore 15, the larger diameter of which is disposed in the region of the larger outer diameter of the delivery valve holder 7. The delivery valve holder forms a valve chamber 17, in which chamber a -8cylindrical delivery valve member 19 is disposed. The delivery valve member 19, on its side facing the connecting sleeve 13 and the fuelinjection point, comprises wing-shaped guide surfaces 21. The guide surfaces in their dimensioning, for example by means of the provision of several grooves. are reduced with regard to the remaining outer diameter of the delivery valve member 19. The guide surfaces 21 protrude into a bore section of the through bore 15 so that the delivery valve 19 is axially guided and a through flow of fuel from the valve chamber 17 into the connecting sleeve 13 is possible.

The delivery valve 19 comprises a valve sealing surface 23 on its end face remote from the connecting sleeve 13, with which valve sealing surface it cooperates with a flat valve seat surface 25 at a disc-shaped valve body 27 comprising an axial through opening 33. The valve body 27 by means of a thread 29 is screwed into the delivery valve holder 7. The valve body 27 delimits the valve chamber 17 on the side remote from the connecting sleeve 13. The valve body 27 comprises in addition a flange 31 at its end remote from the valve chamber 17 with which it comes into position at one of the end faces of the delivery valve holder 7. The delivery valve member 19 is installed with axial play into the valve chamber 17 -9and comprises an annular shoulder 35 at its end facing the valve body 27, against which shoulder a compression spring 37 lies. The compression spring 37 bears on the one side against an annular groove 39 in the front wall of the valve chamber 17, which front wall faces the connecting sleeve. The compression spring 37 holds the delivery valve member 19 in position against the valve body 27. An annular step 41, produced by a reduction in the area of crosssection, in the region of the wing-shaped guide surfaces 21, cooperates with the front wall 43 of the valve chamber 17. The front wall 43 defines the connecting sleeve 13. in order to define the opening stroke of the delivery valve member 19, wherein the front wall 43 forms a stop.

The delivery valve 19 comprises on its inside a stepped through bore 45. The stepped through bore 45 widens outwardly to form a larger diameter from a middle diameter at the connecting sleeve side inlet over a conical widening region forming a valve seat 47 and with this exits at the end face facing the valve body 27. In addition, a throttle 48 is disposed between the connecting sleeve side inlet and the valve seat 47. The region widening in diameter forms a valve chamber 49 in the delivery valve member 19. in which a non-return valve 51 is disposed. The non- -10return valve 51 is formed from a non-return valve member 53, in the form of a guided cone having through openings 55, a return spring 57 and an annular spring plate 59. The return spring 57 thereby holds the nonreturn valve member 53 in position at the valve seat 47 with a conical sealing surface 61 and on the other side bears against the spring plate 59, which spring plate is fixed in the through bore 45 by means of a securing ring 63.

For the purpose of a reliable sealing of the high-pressure line from the outside and to the valve chamber 17. the annular shoulder 9 of the delivery valve holder 7 comprises a biting edge 65 and the flange 31 of the valve body 27 comprises a biting edge 165, which edges cooperate in a coaxial direction towards the guide bore 3 with the contiguous pump housing wall in the region of the step 11 or end face of the delivery valve holder 7 respectively.

For the purpose fixing the preassembled delivery valve and holding assembly 1 in the pump housing 5, a nut 67 is screwed in by means of a thread 69 disposed on the peripheral surface of the part of the connecting sleeve 13 which protrudes out of the pump housing 5. The nut 67 clamps the delivery valve holder 7 against the pump housing 5.

In order to be able to screw the valve body 27 as firmly as possible against the delivery valve holder 7, the through bore 33 comprises in addition a profile in the valve body 27, which profile can be engaged by a screwing tool.

The delivery valve in accordance with the invention operates in the following manner.

When fuel reaches the injection point for the internal combustion engine during the operation of a fuel-injection pump into which the delivery valve 1 described above is installed, the delivery valve closing member 19 is raised from the valve seat 25 of the valve body 27 under the pressure of the fuel flowing out of the pump working chamber. The delivery valve 1 opens and the fuel flows, by way of the through bore 33, the valve chamber 17 and the wingshaped guide surfaces 21, into the connecting sleeve 13 and further to the fuel-injection point. If the delivery pressure of the fuel falls at the end of the fuel delivery, the force of the fuel flowing against the delivery valve closing member is no longer sufficient to hold the delivery valve closing member 19 closed against the force of the compression spring 37, the delivery valve closing member 19 returns to its valve seat 25 and the delivery valve 1 closes. Subsequent to this sudden interruption of the delivery -12pressure waves oscillate in the enclosed volume between the delivery valve 1 and the fuel-injection point.

In order to avoid a secondary fuel injection at the fuel-injection point caused by the above circumstances, the pressure level of the peak pressures of the pressure waves in the high-pressure line is then reduced by means of the non-return valve 51 to a predetermined value, whilst the fuel lifts the valve closing member 53 of the non-return valve, against the force of the return spring 57. from its valve seat 47 and, by means of the through openings 55, the valve chamber 49 and the through duct 33, flows back into the pump working chamber which is now relieved of pressure at the end of the high-pressure delivery phase.

The second embodiment. illustrated in Figure 2, differs from the first in the type of delivery valve 1 and non-return valve 51 disposed therein.

The delivery valve 1 is formed of a number of parts and comprises a cylindrical spring holder 71, which is installed into the valve chamber 17 and held in position at the front wall of the valve chamber 17, which wall faces the connecting sleeve 13,.by means of a compression spring 37 engaging an annular shoulder 73, which compression spring on the one side bears against a disc-shaped valve member 75. The spring -13holder 71 comprises an axial through stepped bore 77. into which through bore issue radial bores 81, issuing from the valve chamber 17, and which through bore extends through the bore 15 in the delivery valve holder 7. The through bore 77 in an extension, beyond the restrictor 48, widens conically outwards to form a larger diameter portion forming a valve seat 47 and a valve chamber 49 in the spring holder 71, which chamber receives the non-return valve 51. The valve chamber 49 is closed on the side remote from the connecting sleeve 13 by a pot-shaped valve cover 79, which valve cover is pressed with its open side into the spring holder 71. The valve cover 79 comprises, in its base, a central bore, into which bore a pin 83 is pressed. The pin 83 on the one side forms, with its end face protruding into the valve chamber 49, a stop 85 for the opening movement of a conical nonreturn valve member 87. The non-return valve member 87 is pressed, by a return spring 57 bearing against the valve cover 79, with its conical sealing surface 61 against the valve seat 47. The pin on the other side is guided, with its end remote from the valve chamber 49, through an axial bore in the valve member 75 in a through stepped opening 89 of the valve body 27. The pin 83 in addition comprises a blind bore 91 issuing from the valve body side end face. The blind -14bore 91 is connected by means of a radial bore 93 to the valve chamber 49 in the delivery valve member 19 and therefore continuously connects the valve chamber 49 by means of the opening 89 in the valve body 27 to the guide bore 3.

Moreover additional through openings 95 are disposed in the valve body 27. The openings 95 are held closed by the valve member 75 working as a valve closing member of the delivery valve 19, wherein the valve member 75 is held, by the compression spring 37, with one of its end faces, forming a valve sealing surface 23, in position at the valve body 27. The opening stroke movement of the valve member 75 is therefore defined by the base side end face of the valve cover 79.

The delivery valve illustrated in Figure 2 functions analogous to that described in the first embodiment, illustrated in Figure 1, wherein the flowing fuel raises the valve member 75 from its seat at the valve body 27 at the commencement of the opening and the fuel then flows, by way of the through openings 95, into the valve chamber 17 and further, by way of the radial bores 81 and the through bore 77, in the spring plate 71. into the connecting sleeve 13.

After the fuel-injection valve has closed at the fuel-injection point and the valve member 75 is placed -is- upon the valve body 27, the high fuel pressure in the injection line and in the connecting sleeve 13 is released in a known manner by the non- return valve 87, wherein, after the non-return valve member 87 has been pushed open, the fuel flows back out of the valve chamber 49 by way of the bores 91, 93 in the pin 83 and the opening 89 into the pump working chamber side part of the guide bore 3.

The advantage of the embodiment described in Figure 2 consists of the fact that the non-return valve member 87 and the valve member 75 are separated from each other and dynamic influences during the opening and closing of the valve member 75 have no effect upon the non-return valve member 87. In contrast, in the embodiment described in Figure 1, the non- return valve member 53 moves in association with the delivery valve member 19.

The third embodiment shown in Figure 3 illustrates a further form of the embodiment of the delivery valve holder which in this embodiment is assembled from two parts, a connecting sleeve 313 and a threaded sleeve 101.

The connecting sleeve 313 comprises a head piece 103 and a shank 105, with which shank it protrudes into the guide bore 3 of the pump housing 5 and with the end of this shank. remote from the head piece 103, -16it is screwed into the threaded sleeve 101 receiving the delivery valve 1. The end face of the threaded sleeve 101, which face is facing the connecting sleeve 313, in addition carries, analogous to Figure 1, a biting edge 65. The biting edge seals the pump working chamber side part of the guide bore 3. Moreover, a further biting edge 365 is disposed at the side of the head piece 103 of the connecting sleeve 313, which side faces the shank 105, and which biting edge cooperates with the wall of the pump housing.

The clamping of the two parts of the delivery valve holder 7. to each other or against the pump housing 5, is achieved by the screw connection between the connecting sleeve 313 and the threaded sleeve 101, wherein, in addition, a profile is incorporated into the region of the through bore 15 in the connecting sleeve 313, which region issues from the head piece 103, and which profile can be engaged by a screwing tool.

With the embodiment of the delivery valve, in accordance with the invention, as a preassembled delivery-valve and holder assembly it is therefore possible to reduce the assembly costs when installing the delivery valve into the housing of the fuelinjection pump, wherein, by means of the arrangements. in accordance with the invention. of the sealing -17 biting edges it is possible to dispense with the sealing surfaces which are costly to produce with regard to the processing tolerances.

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Claims

1. A delivery valve for installation in a delivery line between a pump working chamber of a fuel-injection pump and an injection point at the internal combustion engine to be supplied from this injection point, comprising a delivery valve holder having a connecting sleeve and a through duct, a valve body having a valve seat, which is clamped to the delivery valve holder and through which said through duct also extends and having a delivery valve closure member, which is disposed between the said valve seat and a compression spring, supported in a valve chamber formed from a widening in the cross-sectional area of the through duct of the delivery valve holder, the delivery valve closure member having a sealing surface which cooperates with said valve seat, wherein the delivery valve holder is screwed to the valve body in a sealing manner and, with this valve body and the delivery valve member disposed between them, forms a preassembled delivery-valve and holder assembly, which assembly is installable and clampable in a guide bore of a pump housing, for which purpose the delivery valve holder has a shoulder at a transition from the connecting sleeve to a larger diameter part of the delivery valve holder, which,, larger diameter part - 19receives the valve chamber, and with which shoulder the delivery valve holder can be brought into position in a sealing manner at an annular step of a bore connected to the pump working chamber at the transition of this bore to the guide bore, and wherein the connecting sleeve protrudes out of the pump housing through the guide bore, and is clamped at this point to the pump housing into a sealing position of the shoulder and is connectable to the delivery line.

2. A delivery valve according to claim 1, wherein the valve body has a flange having a biting edge with which it comes into position at the face of the delivery valve holder facing the pump working chamber.

3. A delivery valve according to claim 1 or 2, wherein the shoulder of the delivery valve holder is annular and has a biting edge by means of which the valve holder is brought into position at the annular step of the guide bore in the pump housing.

4. A delivery valve according to claim 1, wherein the delivery valve holder is formed from two parts nd consists of a threaded sleeve, receiving the delivery valve member, and a connecting sleeve screwed to this threaded sleeve.

5. A delivery valve according to claim 4, wherein the part of the delivery valve holder which -20forms the connecting sleeve, comprises a head piece which is larger in diameter with respect to a shank piece guided in the guide bore in the pump housing, which head piece protrudes out of the pump housing, and a biting edge is disposed at the end face of the head piece, facing the pump housing, and cooperates with the wall of the pump housing.

6. A delivery valve according to claim 5, wherein the biting edge of the head piece, in addition to the first biting edge disposed at the threaded sleeve, seals the guide bore.

7. A delivery valve according to claim 1, wherein the delivery valve is formed as a flat seat valve, the valve member of which is axially guided by means of wing-shaped guide surfaces on the side facing the connecting sleeve in a part of the through duct of the delivery valve holder.

8. A delivery valve according to claim 1, wherein the valve member comprises a through duct formed as a stepped bore, the larger crosssection of which forms a valve chamber, in which a non-return valve, for opening towards a pump working chamber, is installed.

9. A delivery valve according to any one of the preceding claims, wherein the two-part delivery valve holder is clamped, by means of the screw connection of -21both parts, to the pump housing.

10. A delivery valve according to claim 1, wherein the delivery valve is formed as a flat seat valve having a discshaped valve member, which valve member is guided by means of a central bore on a pin, which pin is disposed between the valve body and a spring holder installed into the valve chamber.

11. A delivery valve holder according to claim 10, wherein a pot-shaped part, connected at the edges of its open side to the spring holder, is disposed on the pin the outer lying base of which forms a stop for the disc-shaped valve member.

12. A delivery valve according to claim 11, wherein the pot-shaped part together with the spring holder enclose a non-return valve chamber, in which chamber is disposed a non-return valve member, cooperating with a valve seat at a duct in the delivery valve holder leading to the through duct of the delivery valve holder, which non-return valve member is pressed against the valve seat by a valve spring, bearing against the potshaped part, wherein by way of bores in the pin and a bore in the valve body a permanently open connection between a pump working chamber and the non-return valve chamber can exist.

13. A delivery valve constructed and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

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