GB2258015A

GB2258015A - Delivery valves for fuel-injection pumps.

Info

Publication number: GB2258015A
Application number: GB9214628A
Authority: GB
Inventors: Uwe Kuehn
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1991-07-10
Filing date: 1992-07-09
Publication date: 1993-01-27
Anticipated expiration: 2012-07-09
Also published as: JPH05195910A; DE4122767A1; GB2258015B; GB9214628D0

Description

2258J15

-1DESCRIPTION DELIVERY VALVES FOR FUEL-INJECTION PUMPS

The invention relates to delivery valves or pressure valves for fuel injection for internal combustion engines.

In such valves the change in section or transition from the annular groove of a guide body of the delivery valve closure element to its seating surface is an important criterion for the flow behaviour of the pressure medium at this point. A delivery valve of this type is known from EP-B-01 43 296, Fig. 2, where one lateral boundary wall of the annular groove is formed by the conically shaped seating surface of the delivery valve closure element. This type of design provides good flow characteristics, as the fuel can flow laminarly between the valve body and the delivery valve closure element without striking an edge which causes a turbulent flow. The disadvantage of this transition, however, 14es in the chronological sequence of the cross-sectional opening. In such case, insufficient through-flow area is opened during lifting of the delivery valve closure element by means of the fuel. This disadvantage was avoided in other known delivery valves, e.g. DE-B-356 355 33 by a shoulder. The lateral boundary wall of the annular groove, which has -2a right-angled cross-section changes here directly into the conical- shaped seating surface. This design does in fact produce a rapid cross- sectional flow opening owing to the fact that the contact edges of the seating surfaces rapidly move away from each other, but is extremely unfavourable for the flow as an edge, which severely diverts the flow, is formed at the changeover point between the annular groove and seating surface. Severe turbulence in the fuel flow occurs at this edge, which can result in a loss of energy as well as tendencies to cavitation and erosion.

The invention resides in a fuel delivery valve for installation in a supply line between a pump working chamber of a fuel-injection pump and the point of injection of the internal combustion engine to be supplied, the delivery valve having a valve body fitted with a valve seat, the valve body providing a through channel which ends at the valve seat which enlarges conically from the through channel, and having a delivery valve closure element which has a conically-shaped seating surface and is pressed onto the valve seat by means of a pressure spring fixedly supported on the housing of the pressure valve and which provides on its side facing the pressure spring with, a guide body which is inserted into the through -3channel of the valve body and provides a flow through cross sectional area, the guide body having an annular groove, whose lateral boundary wall directly borders an edge limiting the seating surface in the direction of the valve seat, the diameter of the edge being smaller than the internal diameter of the valve body, which forms the through channel, the lateral boundary wall is arcuate as seen in the longitudinal section through the longitudinal axis of the delivery valve.

This has the advantage that, without throttling the flow of fuel in the region of the valve seat and the favourable flow supply associated with throttling, it is possible to guarantee a rapid opening of a large crosssectional area of nozzle aperture. The disadvantages of the known solutions are avoided by making a change in the cross section in the form of a radius, a parabola or a combination of a chamfered edge and radius. In this way, the solution in accordance with the invention facilitates a problemfree use in fuel-injection Dumps and can above all be considered for those pumps, which have high fuel pressures, as the disadvantages described of the known solutions are particularly apparent with high fuel pressures.

The invention is further described. by way of example, with reference to the accompanying drawings, in which: - Fig. 1 is a longitudinal section through the delivery valve in accordance with the invention the closed position; Fig. 2 is a fragmentary section showing the change in section from the annular groove to the seating surface of- the delivery valve closure element, in the form of a radius; Fig. 3 is a similar view showing the change in section in the form of a parabola; and Fig. 4 is the change is section corresponding to Fig. 2 comprising a combination of a chamfered edge and a radius.

Figs. 2, 3 and 4 are confined to an illustration of the significant part of the invention.

Fig. 1 shows a fuel dell-Very valve in accordance with the invention the significant part of which, indicated by the circle, is illustrated to an enlarged scale in Figs. 2 to 4. The delivery valve is located in a feed line (not illustrated) between a pump working chamber of a fuel-injection pump and an injection valve. It is guided in a housing (also not illustrated in more detail) and comprises a tubular valve body 1 fitted in this example with a collar 11, the valve body 1 having at its side facing the collar 11 a conical valve seat 2 forming the internal in -5diameter of a through channel 3 and a cylindrical delivery valve closure element 4 which is axially movably guided in the through channel 3. The delivery valve closure element 4 comprises on its side protruding into the through channel 3 of the valve body 1, a guide body 6 having four guide vanes 12; flow passages are formed between the guide vanes 12 in conjunction with the through channel 3. At its juncture with this guide body 6, the valve closure element 4 forms a conical seating surface 8 by means of an expanded cross section and its diameter tapers again in a further axial continuation and at the same time forms a right-angled shoulder 13 on the peripheral surface of the valve closure element 4. The shoulder 13 forms a resting surface for a pressure spring 5 which is designed as a annular spring and which envelops the delivery valve closure element 4, and which at the other end is fixedly supported on the delivery valve housing and axially loads the delivery valve closure element 4. An annular groove 7 which is directly contiguous to the seating surface 8 of the delivery valve closure element 4 is formed in the guide body 6 of the valve closure element 4. The annular groove 7 separates the guide vanes 12 and the seating surface 8 from each other and at the same time forms a changeover region or an accumulating region -6between the flow passages in the region of the guide vanes and the through-flow cross-sectional area between the valve seat 2 and the seating surface 8 of the delivery valve closure element 4. The cone angle of the seating surface 8 of the delivery valve closure element 4 is larger than that of a seating surface 10 on the valve seat 2. In this way, the delivery valve is closed by the seating surface 8 of the valve closure element 4 engaging an edge 20 of the valve seat 2, the edge 20 formina the boundary of the seating surface 10 in the direction of the pressure spring 5. Thus, the diameter of the edge 20 is larger than that of the through channel 3, whereas the diameter of an edge 9 of the valve seating surface 8, the edge 9 bordering on the annular groove 7 is slightly smaller than that of the through channel 3. The shape of the lateral boundary wall 14 of the annular groove 7 i.e. the lateral boundary wall or transition 14 bordering on the seating surface 8, from the internal diameter of the annular groove 7 to the diameter of the edge 9 has at the same time a considerable influence on the flow behaviour of the fuel flowing by and on the chronological sequence of the crosssectional opening of the valve. on the delivery valve in accordance with the invention, a shape of a lateral boundary wall 14, which -7characterises the region of the change in section from the annular groove 7 to the seating surface 8, is designed in accordance with Fig. 2 in the longitudinal section through the longitudinal axis of the delivery valve like the arc of a circle with a radius 16, the radius 16 beginning at the edge 9, facing the guide body 6, of the conical-shaped seating surface 8 of the delivery valve element 4 and is designed in such a way that, during the opening stroke of the delivery valve closure element 4, the cross sectional area of flow which occurs between the edge 9 and the seating surface 10 of the valve body 1 is smaller than or identical in size, during the entire lifting movement, to the cross-sectional area of flow which is formed between the seating surface 10 and the lateral boundary wall 14. A design which easily meets the demand for a favourable flow behaviour and a rapidly opening valve cross section is achieved, if the radius the lateral boundary wall 14 is equal to the 16 of 1. difference between the radius of the through channel 3 and the cross sectional radius of the annular groove 7. A further design of the change in section or transition is illustrated in Fig. 3, where the lateral boundary wall 14 in the longitudinal section is the shape of a parabola.

Analogous to Fig. 2, Fig. 4 shows a further possibility of the design of the change in section or transition from the annular groove 7 to the seating surface 8. The lateral boundary wall 14 begins here at the edge 9 of the seating surface 8 having a chamfered edge 17 which changes further on into a radius 16.

With the examples illustrated in Figs. 1 to 4 it is possible, despite a favourable rapid and large cross-sectional opening, to achieve a good flow supply of through-flowing fuel and to avoid throttling and turbulences in the region of the valve seat, which in turn results in a reduction in the damage caused by erosion and cavitation. The delivery valve described functions in the known way, in that the fuel flowing through the guide body 6 against the seating surface 8 of the valve closure element 4, raises the valve closure element 4 from the valve seat 2, against the force of the pressure spring 5 and when a flow crosssectional area at the closure element 4 between the valve seat 2 and the seating surface 8, with the fuel flowing by way of the cross- sectional opening into the delivery valve housing and from there into an injection line. With the aid of a change in section, which is favourable for the flow, on delivery valves for fuel-injection pumps between the seating surface 8 -9of the delivery valve closure element 4 and the guide body 6, it is therefore possible to achieve high injection pressures and short valve opening times, without at the same time shortening the serviceable life of the delivery valves.

Claims

-10CLAIMS

1. A delivery valve for installation in a supply line between a pump working chamber of a fuelinjection pump and the point of injection of the internal combustion engine to be supplied, the delivery valve having a valve body fitted with a valve seat, the valve body providing a through channel which ends at the valve seat which enlarges conically from the through channel, and having a delivery valve closure element which has a conicallyshaped seating surface and is pressed onto the valve seat by means of a pressure spring fixedly supported on the housing of the pressure valve and which provides on its side facing the pressure spring, with a guide body which is inserted into the through channel of the valve body and provides a flow-through cross-sectional area, the guide body having an annular groove, whose lateral boundary wall directly borders an edge limiting the seating surface in the direction of the valve seat, the diameter of the edge being smaller than the internal diameter of the valve body, which forms the through channel, the lateral boundary wall is arcuate as seen in the longitudinal section through the longitudinal axis of the delivery valve.

2. A delivery valve as claimed in claim 1, in which the arc is at least in part the arc of a circle.

3. A delivery valve as claimed in claim 2, in which the radius of the circular curve of the lateral boundary wall corresponds to the total of half the difference between the diameter of the through channel and the internal diameter of the annular groove.

4. A delivery valve as claimed in claim 2, in which the shape of the lateral boundary wall commences from the edge of the seating surface as a chamfered surface, which is then continued in a radius.

5. A delivery valve as claimed in claim 1, in which the arc is parabola.

6. A delivery valve as claimed in any preceding claim, in which a seal is produced by line contact between a seating surface of the valve seat of the valve body and the seating surface of the delivery valve closure element and the cone angle of the seating surface of the delivery valve closure element is larger than the angle of the conical valve seat in the valve body.

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