Quantity control valve and high-pressure pump with quantity control valve

A quantity control valve comprises a valve needle configured to move in an axial direction, a damping chamber having a wall, and a valve element delimiting the damping chamber. The valve needle is configured to move the valve element in an opening direction. A gap is defined between the wall of the damping chamber and the valve element. The gap has at least one recess and connects the damping chamber to a flow duct.

This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2012/072673, filed on Nov. 15, 2012, which claims the benefit of priority to Serial No. DE 10 2011 089 288.5, filed on Dec. 20, 2011 in Germany, the disclosures of which are incorporated herein by reference in their entirety.

The disclosure relates to a quantity control valve and to a high-pressure pump having a quantity control valve.

BACKGROUND

Quantity control valves, in particular for metering a fluid, for a high-pressure pump arranged downstream are known. For example, they are used as quantity control valves in common rail fuel systems on motor vehicles in order to control the fuel flow delivered by a high-pressure feed pump to the common rail. Such quantity control valves can be actuated electromagnetically. They comprise a needle/armature assembly. An electromagnet, which is part of the needle/armature assembly, and a spring act on a valve element of the quantity control valve. Particularly at low speeds, the impact of a needle/armature assembly in the open and closed end positions of the quantity control valve leads to excitation of vibration, which has noticeable disadvantageous audible and mechanical effects.

DE 10 2009 046 079 A1 has disclosed a quantity control valve which has a damping device that comprises a fluid container bounded by a moving piston. The piston is arranged in such a way that it is acted upon by the valve element shortly before impingement upon the stop and thus pushes fluid out of the fluid container through a restriction.

In WO 2011 067026 A1, a description is given of a quantity control valve which has a hydraulically acting shield that keeps any backflow at least partially away from a valve element. The shield is a pot-shaped component that is securely connected to a valve housing. The shield is arranged in such a way in relation to the valve element that an axial end face of the valve element is covered by the pot-shaped component.

SUMMARY

The problem underlying the disclosure is solved by a quantity control valve. Advantageous developments are indicated in the claims. Features important for the disclosure can furthermore be found in the following description and in the drawings, wherein the features may be important for the disclosure both in isolation and in various combinations, even if there is no further explicit reference to this fact.

It is a basic concept of the disclosure that a damping device for a quantity control valve can be created by using the valve element as an immersed body in combination with a pot-type damping chamber, said damping device having at least one hydraulic restriction. These restrictions can be configured in such a way that the damping effect varies as a function of the position of the valve element relative to the damping chamber. It is thereby possible to adapt the speed profile of the valve element to various uses. It is particularly advantageous here that the disclosure is integrated directly into the quantity control valve without additional components. Thus, the disclosure does not give rise to any additional costs.

Moreover, the damping device according to the disclosure is insensitive to scatter in the component dimensions, which is unavoidable in any mass production process.

The quantity control valve according to the disclosure has the advantage that the excitation of noise is reduced and, furthermore, the robustness of the quantity control valve is increased by reducing a speed of impact of a valve element on a stop. The reduced speed at impact also reduces the risk that the valve element will rebound from the stop against the needle/armature assembly. Consequently, the reduced mechanical stress allows a reduction in the moving masses, that is to say the needle can be of lighter construction and hence the magnetic circuit can also be made weaker. The disclosure thus also leads to a reduction in the electric power loss by the electromagnetically actuated quantity control valve.

The damping device according to the disclosure for the quantity control valve operates fundamentally as follows: during an opening movement, the needle/armature assembly of an actuator strikes a plate-shaped valve element and raises the latter from a resting seat against a spring force. The valve element, for its part, acts on the fluid present in the damping chamber. In this case, the fluid is put under pressure and escapes from the damping chamber through a gap formed between the valve element and a wall of the damping chamber. Owing to the restriction effect of the gap, the fluid can escape from the fluid container only slowly, and the valve element is retarded in an effective manner. As a result, the speed of impact of the valve element on a stop is reduced and noise evolution decreases.

Because the narrow gap formed between the plate-shaped valve element and a wall of the damping chamber depends relatively heavily on the manufacturing tolerances of the valve element and of the wall, it is, according to the disclosure, provided with at least one but preferably a plurality of recesses (e.g. three) of defined size (cross section and depth). These recesses widen the gap in some areas. The gap is designed as a sliding fit between the plate-shaped valve element and the wall and is used primarily to guide the valve element.

The effective flow cross section formed, in particular, by the recess cross-sectional areas arranged perpendicularly to the direction of flow of the fluid is very much larger than the flow cross section of the gap. The unavoidable manufacturing tolerances of the damping chamber and the valve element therefore now affect only the guidance of the valve element but not the damping behavior of the quantity control valve. In the quantity control valve according to the invention disclosure, the effective flow cross section depends especially on the cross-sectional areas of the recesses. As a result, the desired restriction effect can be determined by means of the dimensions and shape of the recesses and not by the width of the gap between the wall and the valve element. Here, the manufacturing tolerances of the recesses have only a slight effect on the restriction effect, and therefore the scatter in the damping behavior of different instances of a mass-produced quantity control valve is low.

This effect can be achieved especially if the proportion of recesses on the periphery of the gap is less than 50%, preferably less than 30%.

A solution which is simple in terms of manufacturing technology envisages that the at least one recess should extend radially outward in the wall of the damping chamber or radially inward in the valve element, orthogonally to a longitudinal axis of the quantity control valve. The damping chamber can be produced as a formed sheet metal part or from plastic. In the latter case, it can be an integral part of a housing of the quantity control valve.

In order to be able to adapt the damping behavior of the valve element as well as possible to the conditions of use, provision is made to vary the free flow cross section of the gap as a function of the position of the valve element relative to the damping chamber.

An embodiment according to the disclosure envisages that a depth T of the recess is less than the depth of the gap. The depth of the gap is limited by a first projection, on which the valve element abuts in the open position thereof.

If the depth of the recesses is less than the abovementioned gap, the valve element covers the recess completely on its way toward the open position, and only the effective flow cross section formed by the gap is then opened to the escaping fluid. As a result, the restriction effect is intensified and the speed of the valve element is reduced further. As a result, opening of the quantity control valve takes place in two stages. In the first stage, a relatively large effective flow cross section is available, formed by the radial gap and the recess. The fluid can thus escape quickly and with little damping from the damping chamber, and the valve element moves quickly into the open position. The second stage is activated when one edge of the valve element projects beyond a second projection and hence the recess is completely covered. The effective flow cross section is then smaller than in the first stage. As a result, the fluid escapes more slowly from the damping chamber. As a result, the valve element is retarded even further and strikes against the first projection with a further reduced speed. It is thus advantageously possible to combine a short opening time of the quantity control valve with very little noise evolution.

Another embodiment according to the disclosure envisages that the recess tapers from one (front) edge toward a constriction. This ensures that the effective flow cross section decreases continuously in the direction of the stop, that is to say in the direction of the first projection. A continuously increasing restriction effect is thus achieved, the closer the valve element comes to its stop. This results in the same advantages as already explained above.

DETAILED DESCRIPTION

The same reference signs are used for functionally equivalent elements and dimensions in all figures, even in the case of different embodiments.

FIG. 1shows a fuel system1of an internal combustion engine in a greatly simplified illustration. A high-pressure pump2(not explained specifically) designed as a piston pump is connected upstream, via a suction line3, a priming pump4and a low-pressure line5, to a fuel tank6. A high-pressure accumulator8(“common rail”) is connected downstream to the high-pressure pump2via a high-pressure line7. A quantity control valve10having an electromagnetic actuating device—referred to below as actuator11—is arranged hydraulically between the low-pressure line5and the high-pressure pump2and forms the inlet valve of the high-pressure pump2. Other elements, such as the outlet valve of the high-pressure pump2, are not shown inFIG. 1. It is self-evident that the quantity control valve10can be integrated into the high-pressure pump2.

During the operation of the fuel system1, the priming pump4pumps fuel from the fuel tank6into the low-pressure line5.

The high-pressure pump2draws fuel from the low-pressure line5and pumps it into the high-pressure line7and the high-pressure accumulator8.

Because the high-pressure pump2is a piston pump, it has a suction stroke and a delivery stroke. The delivery volume of the high-pressure pump2is controlled by the quantity control valve10, e.g. by remaining open for a longer or shorter time during a delivery stroke of the high-pressure pump2.

FIG. 2shows a partial longitudinal section of the quantity control valve10. The quantity control valve10comprises a housing12, a valve needle14acted upon by a solenoid valve spring13and having a magnet armature15arranged thereon, a plate-shaped valve element16and a valve seat17(“resting seat”) fixed relative to the housing and interacting with said element. The elements of the quantity control valve10are substantially rotationally symmetrical with respect to a center line18. The valve needle14and the magnet armature15form a needle/armature unit.

InFIG. 1, the high-pressure pump2is arranged to the right of the quantity control valve10, and the low-pressure line5coming from the priming pump4is arranged to the left of the quantity control valve10.

During a suction stroke of the high-pressure pump2, the valve element16rises from the valve seat17(not shown inFIG. 2), with the result that fuel can flow out of the low-pressure line5, through the gap that then exists between the valve element16and the valve seat17, and through an annular flow duct20in the direction of the high-pressure pump2.

The annular flow duct20is delimited on the outside by the housing12and on the inside by an inner part23. The inner part23can be part of the housing12or can be a separate component which is connected to the housing12.

The inner part23is of pot-shaped configuration with a “bottom”24and a substantially cylindrical “wall”25. On its end facing the valve member16, the inner part23has a damping chamber26. In the damping chamber26there is a spring30, which presses the valve element16against the valve seat17.

The inner part23can be produced from plastic or metal, e.g. as a formed sheet metal part.

The plate-shaped valve element16projects at least partially into the inner part23and in this way delimits the damping chamber26.

The damping chamber26is filled with fuel and is connected to the flow duct20via a constriction27acting as a restrictor.

A first projection28is formed in the wall25of the inner part23or of the damping chamber26, forming a stop for a surface29of the valve element16facing away from a valve seat17in an open position of the valve element16. The first projection28does not have to be of radially encircling configuration. It is sufficient for the support of the valve element16if the first projection28comprises two or more segments distributed over the periphery and arranged in the annular shielding section25. One such segment with the reference sign28is illustrated in the lower part ofFIG. 2, while there is no such segment in the upper part ofFIG. 2.

The illustration inFIG. 2shows the quantity control valve10in the closed position. In the closed position, the valve element16rests on the valve seat17of the housing12. In an open position, the valve element16is supported against the first projection28of the annular shielding section25.

The quantity control valve10operates as follows:

If the actuator11is deenergized, the spring force of the solenoid valve spring13moves the valve needle14and the magnet armature15securely connected thereto to the left in the drawing. During this process, the valve needle14strikes against the valve element16and moves it likewise to the left. As a result, the fuel in the fluid container26is put under pressure and must escape into the flow duct20through the constriction27. This is indicated inFIG. 2by an arrow (without a reference sign). In this process, the constriction27acts as a restrictor, with the result that the fuel can escape only slowly. The resulting hydraulic force has a damping effect counter to the spring force of the solenoid valve spring13, with the result that the speed with which the valve element16strikes against the first projection28is reduced.

When the actuator11is energized, the valve needle14moves to the left in the drawing, with the result that the valve member16can move in the direction of the valve seat17, like a conventional inlet valve.

As an alternative, the quantity control valve10can also be closed when deenergized.

FIG. 3shows an isometric illustration of the inner part23as seen from the valve element16. For clarity, the valve element16is shown sectioned. The constriction consists essentially of a plurality of recesses32distributed over the periphery of the gap31. As an alternative, the recesses32can also be formed in the valve member16. Overall, the annular area of the gap31and the cross-sectional areas of the recess32perpendicular to the center line18of the quantity control valve10form the effective flow cross section of the constriction27. In this case, the recesses32are decisive for the damping behavior of the constriction27because a majority of the fuel displaced from the damping chamber26or flowing back into the damping chamber26flows through the recesses32.

This also means that dimensional deviations due to manufacture in the diameters of the valve element16or the wall25have only a slight effect on the damping behavior of the damping chamber26. As a result, the scatter between different examples of mass-produced quantity control valves10is greatly reduced, bringing considerable advantages in the operation of the internal combustion engine.

In the first illustrative embodiment, which is illustrated inFIGS. 2 and 3, the extent of the recess32into the damping chamber26along the center line18is greater than that of the projection28serving as a stop for the valve element16; however, it does not reach the bottom24of the inner part23.FIG. 4shows a variant in which the recess32reaches as far as the bottom24.

FIG. 5shows a variant in which the recess32ends ahead of the first projection28. In the illustrative embodiment shown inFIG. 5, a depth T of the recess32is limited by a second projection34. This ensures that the valve element16covers the effective flow cross section of the recess32before it strikes against the first projection28. In this way, a large total flow cross section is available at the beginning of the opening movement of the valve element16, said cross section being composed of the flow cross section of the gap31and the flow cross sections of the recesses32. As a result, the fuel can escape quickly from the damping chamber26, and the valve element16moves quickly in the direction of the first projection28.

As soon as the valve element16has moved as far in the direction of the first shoulder28that it covers the recesses32with its (end) face29facing away from the resting seat17, only the flow cross section of the gap31is then effective, with the result that the damping effect increases and the valve member16is retarded even further before it strikes against the first shoulder28. As a consequence, the valve element16also moves more slowly in the direction of the first projection28. As a result, the momentum of the valve element16upon impact with the first projection28is further reduced. As a consequence of this, the noise which arises during this process is also less. Thus, variable damping depending on the position of the valve member16is achieved. In this case, the damping characteristic that results therefrom has a step.

FIG. 6shows an embodiment of the disclosure similar toFIG. 5, wherein the recess32tapers from one edge36of the wall25toward the constriction27. As a result, the gap31assumes the form of a frustocone in a first section extending from an edge36of the inner part23to the constriction27. The edge36marks the start of the gap31. A second section adjoining this, which extends from the constriction27to the first projection28, is made cylindrical.

The fundamental operation of the embodiment illustrated inFIG. 6is comparable to that inFIG. 5. However, the continuous decrease in the effective flow cross section in the constriction27means that the speed with which the valve element16moves into the open position thereof, i.e. in the direction of the first projection28, likewise decreases continuously. Consequently, the valve element16is retarded in a uniform manner.

In all the embodiments illustrated by means ofFIGS. 2 to 6, the recesses32are formed in the wall25of the inner part23. Of course, the advantages according to the disclosure are also achieved if the recesses32are present in the valve member16. A combination of recesses32in the wall25and in the valve member16is also possible.