GB2273134A

GB2273134A - Delivery valve for a fuel injection pump.

Info

Publication number: GB2273134A
Application number: GB9324264A
Authority: GB
Inventors: Jaroslaw Hlousek
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1992-12-01
Filing date: 1993-11-25
Publication date: 1994-06-08
Anticipated expiration: 2013-11-25
Also published as: GB2273134B; DE4240303C2; JPH06213105A; JP3410526B2; DE4240303A1; GB9324264D0

Description

2273134 DELIVERY VALVE The invention relates to pressure valves or

delivery valves for installation in a fuel delivery line in a pump housing of a fuel injection pump.

In a delivery or pressure valve of the type disclosed in US-A-4577606. Fig. 3. which is disposed in a delivery line between a pump working chamber and a fuel injection point, a flat-seat valve closure member is raised from its valve seat against the force of a spring by virtue of a highly pressurised medium, which medium is carried from the pump working chamber by means of a delivery line to the delivery valve, the delivery valve opening towards the fuel-injection point. At the end of the high pressure delivery, the flat-seat valve closure member in the pump working chp.mber returns to its seat. At the same time an injection valve at the fuel-injection point closes, whereby pressure waves flow to and fro in the enclosed space between the delivery valve and fuel-injection point, which waves are liable to re-open the fuelinjection valve. To avoid this, a port is disposed on the inside of the flat-seat valve closure member, which port forms a valve seat for a non-return valve opening towards the pump working chamber. through which non-return valve the pressure level in the -2delivery line can fall to a static pressure even after the closing of the flat-seat valve closure member, which static pressure is defined by the pre-stress of the return spring of the non-return valve.

A disadvantage arises in the known delivery valve that, through the use of a valve retainer installed into the pump housing, this retainer must in addition be sealed with respect to the the delivery line, which, as well as increased installation space and effort. also demands high precision of manufacture.

In accordance with the invention, there is provided a delivery valve to be incorporated into delivery line extending in a pump housing between a pump working chamber of a fuel-injection pump and a injection point of the internal combustion engine to be supplied by it, comprising a flat- seat valve member opening in the direction towards the fuelinjection point against a resilient force, having a stepped through-bore of which the outlet at the side toward the pump working chamber is formed as a conical valve seat for a non-return valve opening towards the pump working chamber against resilient force, the opening movement of the non- return valve being liTnited by abutting against a stop wherein the non- return valve member has, adjacent to its sealing surface a cylindrically formed part, of which a part facing the h -3pump working chamber is guided in the pump housing accommodating the pump working chamber by its cylindrical peripheral surface directly in a bore part, being of a smaller diameter and at the pump working chamber side, of a stepped bore, the stepped bore having on its transition from the part with the larger diameter to the part with the smaller diameter a flat-seat for the flat-seat valve member and wherein the stepped through- bore of the flat-seat valve member following the conical valve seat passes into an additional stepped bore part being larger in diameter by which part the flat-seat valve member is guided axially on a part of the cylindrical peripheral surface of the non-return valve member remote from the pump working chamber.

This has the advantage that by means of the direct guiding of the nonreturn valve member in a bore in the pump housing, or a cylinder liner of the fuel-injection pump, it is possible to dispense with an additional valve retainer. This results in an embodiment of the delivery valve which is compact, symmetrical and requires a smaller installation space with resultant advantages with regards to cost. By mean of bringing the delivery valve directly into a bore of the pump housing it is possible to dispense with additional components and sealing surfaces other than those of the delivery valve which are purely functional, the result of this is to reduce manufacturing expenses and in addition, because of a reduction in the space required in the pump housing, to increase the stability and therewith the service life of the components accommodating the delivery valve.

It is thus particularly advantageous to allow the cylindrical non-return valve member to slide within the bore of the housing or the cylinder liner and for the flat-seat valve member in turn to be disposed by an inner bore on the cylindrical peripheral surface of the non-return valve member; thus a support for the flat-seat valve member.or an axial valve seat of the bore in the cylinder liner as well as the positioning of the non-return valve member on a valve sat inside the flat-seat valve member are possible without having to machine an additional guidesurface for the flatseat valve member inside the bore accommodating the delivery valve.

The bore accommodating the delivery valve in the cylinder liner thus forms, in an advantageous manner, a shoulder by means of a reduction in diameter, which shoulder serves as a flat-seat for the axial sealing surface of the flat-seat valve.

By means of an advantageous embodiment of the -5non-return valve member, it is possible, during a secure closing function by means of the conical sealing surface, to achieve, by means of a blind bore, the largest possible cross section of through-flow in order to push open the flat-seat valve member and. by means of the radial bores to form an extremely large through-flow cross-sectional area for the overflowing fuel.

In order to reduce the resis'A'-.ance to flow towards the fuel-injection point, flattened areas on the nonreturn valve member can also be disposed at the level of the outlets of the radial bores.

The stop for the opening movement of the nonreturn valve and the locating surface for the return spring acting upon this non-return valve can be formed means of shoulders, which shoulders result from easily produced reductions in the diameter of the bore which guides the delivery valve. The bore accommodating the delivery valve, which bore is in the cylinder liner, is extended from the side remote from the pump working chamber in an advantageous manner axially beyond the cylinder bore containing the pump pistons into the pump housing. The said bore can be closed by a closure screw in the housing which makes a problemfree insertion of the delivery valve and in addition has a projection protruding into bore, which -6projection liMits the opening of the flat-seat valve, a collar of the closure screw serving at the same time as a locating surface for the valve spring acting upon the flat-seat valve. The high-pressure port or connection can be formed as a radial bore issuing into the bore, which results in a high flexibility with regard to its position.

The invention is further described, by way of example, with reference to the accompanying drawings, in which:- Fig 1. is a longitudinal sectional view through a part of a fuel injection pump accommodating a delivery valve in accordance with the invention; and Fig 2. is a sectional view through the delivery valve of Fig 1 in which the arrangement of the flattened areas on the peripheral surface of the delivery valve are represented.

Referring to Fig 1, a cylinder liner 3 having a cylinder bore 5 formed as a blind bore is installed, in a housing 1 of a fuel injection pump. A pump piston 7 is axially guided in the cylinder bore 5 and delimits a pump working chamber 9, which is connected by means of a delivery line 11 to a fuel-injection point formed by an injection valve 13, in the combustion chamber of the combustion engine to be supplied. A delivery valve 17, formed as a pressure v -7equalising valve in this delivery line 11, is disposed in a bore 15 in the cylinder liner 3, which bore connects axially with the cylinder bore 5. The delivery valve 17 comprises a flat-seat valve member 19 opening towards the fuel-injection point 13 and a non-return valve member 21 opening towards the pump working chamber 9. in order to accommodate the delivery valve 17, the bore 15 is formed as a stepped bore, the diameter of which becomes narrower towards the pump working chamber 9 by virtue of several shoulders. The part of the non-return valve member 21 nearest the pump working chamber is cylindrical and is axially guided by. its peripheral surface in a middle region 23 of the bore 15. The front face of the nonreturn valve member 21 remote from the pump working chamber 9 tapers conically and so forms a conical seating surface 25. The flat-seat valve member 19 is similarly cylindrical in shape; it has, however, a larger outer diameter than non-return valve member 21 and is disposed in a region 27 having the correspondingly larger diameter of the stepped bore 15. which bore issues by virtue of a shoulder 45 into the middle region 23 which is smaller in diameter. The peripheral surface of the flat-seat valve member 19 does not touch the wall of the stepped bore 15. The flat-seat valve member 19 has a stepped through-8bore 29, which bore begins at the front face nearest the pump working chamber with a large diameter then tapers conically forming a valve seat 31, extends further with a medial diameter and then once more reduces to a very small diameter. At this last point the diameter forms a restrictor 33. On its outer surface the flat-seat valve member 19 has on its side remote from the pump working chamber 9 an annular shoulder 35 on which a first valve spring 37 engages. The valve spring 37 is supported at its other end upon collar 39 of a closure screw 41 closing the region 27 of the stepped bore 15 at the end remote from the pump working chamber 9 and so holds the flat-seat valve member 19 with its annular front face towards the pump working chamber, which face forms an axially facing sealing surface 43 butting against the shoulder 45 forming a flat valve seat. The sealing surface 43 is thus offset with respect to the cylindrical wall of the region 27 of the stepped bore by a turned groove to provide a sealing surface which can be machined without any problems. The flat-set valve member 19 is guided by its large diameter portion of the throughbore 29 on the side facing the pump working chamber 9 in a sliding manner on the region of the cylindrical outer surface of the non- return valve 21 protruding out of the bore part 33 which guides the non- return 1 4.

-9valve member 21, as also shown in Fig 2. The nonreturn valve member 21 having its conical sealing surface 25 is held pressed against the conical valve seat 31 of the flat-seat valve member 19 by a second valve spring 47, which is weaker than the valve spring 37, this valve spring 47 being supported at one end against an annular shoulder 48 at the front face of the non-return valve member against an annular shoulder 48 at the front face of the non-return valve member 21 facing the pump working chamber 9 and at its other end against a shoulder 49 resulting from a reduction in diameter of the stepped bore 15 in the end at the side facing towards the pump working chamber in the middle region of the bore 15.

To make the through-flow of the fuel, compressed to a high pressure in the pump working chamber 9, through the delivery valve 17 possible,, the non-return valve 21 has an axial blind bore 51 issuing from the front face facing the pump working chamber 9 into which blind bore four radial bores 53 issue. In order to ensure an unhindered through-flow of fuel to the flat-seat valve member 19 and at the same time a safe sliding the nonreturn valve member 21 has in addition, flattened ares 55 on its peripheral surface as represented in Fig 2, which flattened areas extend from the outlet of the radial bores 53 to the -10beginning of the sealing surface 25. In order to limit the opening movement of the delivery valve 17, stops are provided. To this end, a cylindrical projection 57 of the closure screw 41 protrudes into the bore 15 and forms by its front face a stop 59 for the flatseat valve member 19 and a further shoulder is disposed between the shoulder 49 and the middle section of the bore 23 and is formed by the stepped diameter of the bore to form a stop 61 for the nonreturn valve member 21. The continuation of the delivery line 11 after the delivery valve 17 is achieved by means of a high pressure port 63; in the illustrated embodiment by means of a transverse bore issuing into the bore 15. An axial extension of the stepped bore 15 would also be possible here while the high pressure port can be formed out of a liner which can be held by means of a flange fastened to the housing to provide an axial extension of the stepped bore 15.

The delivery valve 17 in accordance with the invention works in the following way. During operation of the fuel injection pump in which the delivery valve 17 is installed in the delivery line 11 in the fuelinjection pump leading to the fuelinjection valve 13 the fuel contained in the pump working chamber 9 is compressed to a high pressure.

-11By means of this high fuel pressure, which also effective on the nonreturn valve member 21 connected to the pump working chamber 9 by means of the bore 15, the flat-seat valve member 19, which sits on the valve seat 45 and on which abuts the non-return valve member 21 during the opening procedure, is raised from its valve seat 45 against the return force of the valve spring 37 so that the fuel can flow by way of the blind bore 51. the radial bores 53 and the opened through-flow cross- sectional area at the flat-seat valve member 19 into the widened bore region 27 of the bore 15 and from there by way of the high pressure connection into the delivery line 11 to the injection valve 13. When at the end of the high pressure delivery, the fuel pressure in the pump working chamber 9 falls, the pressure of the fuel flowing in is no longer sufficient to hold the flat-seat valve member 19 open against the force of the valve spring 37. the flat seat valve member 19 returns to its valve seat 45 and the delivery valve 17 and, as a result of that, also the fuel-injection valve 13 close. In connection with this sudden interruption of the fuel deliveryr pressure waves flow to and fro in the enclosed space between the fuel-injection valve 13 and the delivery valve 17. In order to avoid this causing a renewed opening of the fuel- injection valve 13, the -12pressure level of the peaks of the pressure waves in the delivery line 11 is reduced by means of the nonreturn valve 21 to a predetermined level, in which valve the fuel flowing through the port 29 in the flat-seat valve member 19 against the non-return valve member 21 raises the non- return valve member from its valve seat 31 against the force of the valve spring 47 and further by way of the flattened areas 55, the radial bores 53 and the blind bore 51 flows back into the pump working chamber 9 until the pressure of the fuel flowing back is no longer sufficient to hold the non-return valve member 21 open against the force of the valve spring 47 and the non-return valve member 21 returns to its seating 31. This moment of the closing and therewith the level of the remaining residual pressure is, like the opening moment in the case of the flat-seat valve member 19, is adjustable by means of a pre-stressing of the valve springs 37, 47, which pre-stressing can be changed for example by way of installing spacer pieces. In order to prevent a further raising of the non-return valve member 21 associated with a high spring loading, the flow of fuel as it flows back through the non-return valve member 21 at the restrictor 33 of the port 29 can be restricted by means of the flat seat valve member 19. It is thereby possible through the guiding, in i -13accordance with the invention, of the non-return valve member 21 directly into the bore 15 of the cylinder liner 3 and of the flat-seat valve member 19 on the non-return valve member 21 to dispense with additional components to guide the delivery valve while fully retaining the functional qualities of the delivery valve which considerably reduces the manufacturing expenses. Most of all the flat seat and the shoulders of the stepped bore 15 which serve as stops can be produced in a particularly advantageous manner in a single clamping step of the valve housing and, by means of this minimum number of components along with the simplified assembly only a slight weakening of the walls of the element can be achieved. Moreover the assembly, in accordance with the invention, of the delivery valve can be realised in pump housings which are differently constructed.

Claims

-14CLAIMS

1. A delivery valve to be incorporated into delivery line extending in a pump housing between a pump working chamber of a fuel-injection pump and a injection point of the internal combustion engine to be supplied by it, comprising a flat-seat valve member opening in the direction towards the fuelinjection point against a resilient force, having a stepped throughbore of which the outlet at the side toward the pump working chamber is formed as a conical valve seat for a non-return valve opening towards the pump working chamber against a resilient force, the opening movement of the non-return valve being limited by abutting against a stop wherein the non-return valve member has. adjacent to its sealing surface a. cylindrically formed part, of which a part facing the pump working chamber is guided in the pump housing accommodating the pump working chamber by its cylindrical peripheral surface directly in a bore part. being of a smaller diameter and at the pump working chamber side, of a stepped bore, the stepped bore having on its transition from the part with the larger diameter to the part with the smaller diameter a flat- seat for the flat-seat valve member and wherein the stepped through-bore of the flat-seat valve member following the conical valve seat passes into an c i -15additional stepped bore part being.larger in diameter by which part the flat-seat valve member is guided axially on a part of the cylindrical peripheral surface of the non-return valve member remote from the pump working chamber.

2. A delivery valve according to claim 1 in which the flat-seat valve member has,, at its front face facing the pump working chamber an annular flat axial sealing surface by which it is held against the flat-seat by a valve spring which flat-seat is defined by an annular groove adjacent the wall of the larger diameter part of the stepped bore.

3. A delivery valve according to claim 1 or 2, in which the sealing surface of the non-return valve member working in co-operation with the flat-seat valve member is formed in a conical shape on its side remote from the pump working chamber and in which the front face of the nonreturn valve member facing the pump working chamber has, therein an axial blind bore into which radial bores issue and the non-return valve member has flattened areas on its cylindrical peripheral surface in the region of the outlet of the radial bores. which flattened areas extend as far as the conical valve sealing surface.

4. A delivery valve according to claim 1, 2 or 3 in which the stepped bore of the pump housing is -16further reduced in diameter towards the pump working chamber whilst forming a shoulder which forms the stop for the non-return valve member and in which a compression spring loading the non-return valve member is supported in a part of the stepped bore of a further reduced diameter.

5. A delivery valve according to claim 4 in which the stepped bore is located in pump element accommodating the pump chamber as a pump cylinder blind bore and in which the additional stepped bore part whilst forming a support shoulder for the compression spring of the non-return valve member leads into a bore issuing into the pump working chamber.

6. A delivery valve according to any of claims 1 to 5,. in which the stepped bore accommodating the delivery valve in a cylinder liner in the pump housing is closed at the side remote from the pump working chamber by a closing screw which has a projection protruding into the bore, the front face of which projection forms a stop for the opening movement of the flat-seat valve member.

7. A delivery valve according to claim 6, in which a valve spring, acting on the flat-seat valve member,, is supported at its other end against the collar of the closing screw.

9, 8. A delivery valve according to claim 6 or 7, when dependant from claim 2, in which the stepped bore containing the delivery valve is disposed axially and as a continuation of the cylinder bore in the cylinder liner and in which a radial bore forming a high pressure connection port issues into the region of the stepped bore, which region accommodates the valve spring of the flat-seat valve member.

9. A delivery valve constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.