EP1066465B1 - Fuel injection valve for high-pressure fuel injection - Google Patents

Abstract

The invention relates to a fuel injection valve for high-pressure fuel injection from a central high-pressure line (6) to the combustion chambers of an internal combustion engine. The inventive valve (1) comprises a valve seat (2), a valve ball (3) and a guide element (4) for the valve ball (3). The guide element (4) presses the valve ball (3) against the valve seat (2) in order to close the injection control valve. In an open position, the guide element exposes the valve ball (3) to the effects of a prestressing spring (5). The valve ball (3) is raised above the seat (2) of the valve by means of a high pressure jet that is supplied by a control chamber (7)which cooperates with a second high-pressure line (6) via a discharging outlet port (8) when open. A diffuser (9) is arranged between the valve seat (2) and the outlet port (8). The outlet port (8), diffuser (9) and valve seat (2) form an approximately funnel shape with steep walls, whereby the conical angle thereof is a right to sharp angle.

Description

State of the art

The invention relates to a fuel injection valve for a high-pressure injection according to the preamble of claim 1.

Document EP 0 851 115 A1 shows a fuel injection valve according to the preamble of claim 1.

Such an injection valve is from European patent application 0 661 442 A1 known. Fuel injection valves of this type have a control chamber on, constantly via an inlet throttle bore with a high pressure fuel source is connected via a high pressure line. A valve closing member the fuel injector is held in the closed position until how high the control pressure in the control room is.

The control chamber can be relieved via an outlet throttle bore, which by an injection control valve is applied. Once the injection control valve the drain throttle bore releases, the control chamber is relieved and that Valve closing element of the fuel injection valve goes into its open position over, so that the injection into a combustion chamber of an internal combustion engine can be done. If the injection control valve the drain throttle bore closes again because of the pressure increase in the control room Valve closing element brought back into the closed position.

Speed, accuracy and reproducibility of the opening and Closing movements of the injection control valve are for the quality of the Fuel injection is vital. The reproducibility the opening and closing movements are crucial to the structure of the injection control valve, which essentially consists of a valve seat for opening and closing the outlet throttle bore with a valve ball interacts by a guide member to close and open the Injection control valve pressed onto the valve seat or to open one Spring preload a spring is exposed.

There is a recess in the guide member guiding the valve ball adapted to the diameter of the valve ball, but radial deflections can the ball opposite the ball seat occur when the High pressure jet on the outlet throttle bore radially displaces the valve ball meets. Swinging can also occur until the ball is centered is lifted off the valve seat, and finally through the formation of the Valve seat as a flat cone does not ensure that the valve ball Valve seat without radial displacement and without occurrence of settling processes closes centered during the closing process.

A typical embodiment of the essential structural parts of a Injection control valve shows a section of FIG. 3. The fuel injection valve is about the compression 11 with the central High-pressure line 6 connected, which in turn is connected to a high-pressure fuel source communicates. An inlet throttle bore 10 is a Control chamber 7 is placed under high pressure, which on a valve closing member 12 acts that keeps the fuel injector closed as long as the High pressure is present in the high pressure control room. Via a relief hole, which passes into an outlet throttle bore 8, the control room 7 are relieved, so that the valve closing member, the fuel injector opens and fuel from the central high pressure line 6 into the combustion chambers injects an internal combustion engine. The opening and closing of the drain throttle bore 8 is through an injection control valve with a valve seat 2 a valve ball 3 and a guide member guiding the valve ball 3 4 guaranteed. The flat-conical valve seat is also evident here to recognize an obtuse opening angle α, which is also evident from the publication EP 0 661 442 A1 with FIG. 2 is known.

Any occurrence of settling processes and / or radial dislocations the valve ball opposite the center of the centrally located drain throttle bore reduces the accuracy and reproducibility of the Opening and closing movements of the injection control valve.

The object of the invention is therefore to address the disadvantages of fuel injection valves state of the art to overcome a safe, even closing of the valve ball in the injection control valve ensure and distortion caused by transients or others Valve ball obstruction when closing the injection control valve Reduce.

This task is accomplished by a fuel injector with the features solved according to claim 1.

Advantages of the invention

By placing a diffuser between the valve seat and the Drain throttle bore is advantageously achieved that a higher proportion, compared to the solution according to EP 0 661 442 A1, the kinetic energy of the high-pressure jet emerging from the throttle bore into static pressure is implemented. Because of the larger average diameter of the diffuser opposite the throttle bore, the pressure on an enlarged Act on the surface of the valve ball when opening. Thus the Valve ball evenly and reproducibly centered and lifted radial displacements of the valve ball in relation to the outlet throttle bore are largely reduced.

By forming an approximately steep-walled funnel shape Drain throttle bore, diffuser and valve seat, the funnel shape one has right to acute cone angle α is advantageously achieved, that in contrast to the conventional valve seat with a flat cone drain throttle bore arranged centrally on the cone tip Funnel wall of the valve seat when the injection control valve closes Centering the valve ball supports and radial displacement of the Valve ball opposite the diffuser and the outlet throttle bore prevented. Thus, with the design of the injection control valve according to the invention increased accuracy and in the fuel injector Reproducibility of the opening and closing movements achieved.

Advantageous further developments and improvements of claim 1 Fuel injector specified by the in the dependent Defined features defined claims.

A diffuser is usually a continuous expansion of a minimum diameter to a maximum diameter. The kinetic Energy of a flowing medium increasing and steadily partly in static pressure implemented. In a preferred embodiment of the Invention, the diffuser is designed as a "cross-sectional jump", i.e. minimum and The maximum diameter of the diffuser is the same. This represents an erratic Extension of the outlet throttle bore to the diameter of the diffuser represents what is commonly referred to as the Carnot opening. Such one Carnot opening has the advantage that the drag coefficient ζ by simply changing the ratio between the diameter of the diffuser and the diameter of the outlet throttle bore can be optimized.

In a preferred embodiment of the invention, the ratio is between the mean diameter of the diffuser and the diameter the outlet throttle bore between 1.2 and 2, so that approximately the Resistance coefficient ζ can be set between 0.16 and 9.

In a further preferred embodiment of the invention, the Cone angle α 60 ° to 90 °. In contrast to that from the state of the Technically known flat cone allows this steep wall cone improved centering of the valve ball. With cone angles less than 60 ° the centering of the valve ball is supported more, but can the ball does not protrude deep enough into the diffuser to The smallest possible distance to the outlet throttle bore when the valve is closed Injection control valve to hover. On the other hand, at cone angles α greater than 90 ° the centering effect of the funnel shape becomes increasingly smaller, so that the disadvantages described for the prior art increase.

The valve ball is preferably immersed between 1/5 and 1/10 of its radius r into the diffuser. This can be achieved in an advantageous manner that on the one hand a sufficiently large ball cap of the valve ball from the high pressure jet hit and lifted centered from the valve seat and on the other hand Excessive immersion of the valve ball in the diffuser is avoided.

In a further embodiment of the invention, the maximum diameter D of the diffuser and the length ℓ of the diffuser on each other matched that the valve ball in a closed injection valve Distance of ≤ 0.1 mm, preferably between 30 and 80 microns above Drain throttle bore is positioned. With this distance is preferred ensures that the high pressure jet from the outlet throttle bore at Initially, opening the injection control valve does not just open the valve ball surface acted in the area of the throttle bore, but that the Pressure on the larger surface of a ball cap of the valve ball in the Range of the maximum diameter of the diffuser or valve seat effect.

The length-to-diameter ratio is the proportion of the throttling Drain throttle bore crucial. The smaller the diameter and each the greater the length of a throttle bore, the greater the throttling. With increasing throttling, lower consumption also increases reached fuel running out of the control room. At the same time however, the time for the relief of the high pressure in the control room increases. Therefore, the range from 1 to 20 represents the length-to-diameter ratio the drain throttle bore an optimal compromise between these two extremes.

Furthermore, the diffuser preferably has a length-to-maximum diameter ratio between 0.1 and 0.5. With this length-to-maximum diameter ratio the diffuser is achieved that the flow at the jacket-shaped wall of the diffuser does not come into contact, so that the Friction losses in the diffuser become negligibly small, while the Flow losses due to vortex formation at the step-like transition increase.

Fig. 1

einen Querschnitt durch ein Kraftstoff-Einspritzventil im Bereich eines Ventilsitzes eines Einspritzsteuerventils in einer ersten Ausführungsform der Erfindung;

Fig. 2

einen Querschnitt durch ein Kraftstoff-Einspritzventil im Bereich eines Ventilsitzes eines Einspritzsteuerventils in einer zweiten Ausführungsform der Erfindung; und

Fig. 3

einen ausschnittsweisen Querschnitt im Bereich der wesentlichen konstruktiven Teile eines herkömmlichen Einspritzsteuerventils.

Further advantages, features and possible uses of the present invention result from the following description of exemplary embodiments in conjunction with the drawing. In it show:

Fig. 1

a cross section through a fuel injection valve in the region of a valve seat of an injection control valve in a first embodiment of the invention;

Fig. 2

a cross section through a fuel injection valve in the region of a valve seat of an injection control valve in a second embodiment of the invention; and

Fig. 3

a partial cross section in the area of the essential structural parts of a conventional injection control valve.

Description of the preferred embodiments

Fig. 1 shows a cross section through a fuel injection valve in the area of a valve seat 2 of an injection control valve in a first embodiment the invention. A pressure chamber 7 is above one shown in FIG Inlet throttle bore 10 connected to a central high-pressure line 6 and is therefore under a fuel pressure between 150 and 300 MPa. Via a relief bore 13, which in an outlet throttle bore 8th passes, the control chamber 7 can be relieved when the valve ball 3rd of the injection control valve from the valve seat 2 against a spring preload a spring 5 stands out in the direction of arrow A.

The valve ball 3 is replaced by a valve ball 3 shown in FIG. 3 leading guide member 4 held when opening and closing. The Centering the ball 3 on the valve seat 2 is essential by a steep-walled funnel shape, which has a right to acute cone angle α, which is 90 ° in this preferred embodiment, guaranteed. This can advantageously be the high pressure jet from the outlet throttle bore 8 hit the valve ball 3 centrally and this as soon as a solenoid valve Valve ball 3 relieved of a contact pressure on the valve seat 2 in Raise arrow direction A. Between valve seat 2 and outlet throttle bore 8 is arranged a diffuser 9, in which in this embodiment the The minimum diameter d and the maximum diameter D are the same.

The length-to-diameter ratio of the diffuser 9 is in this embodiment 0.2, and the length-to-diameter ratio of the drain throttle bore 8 is <2. The valve ball 3 dips with an eighth of hers Radius r into the diffuser 9 and is when the injection control valve is closed positioned at a distance of 80 µm above the throttle bore. The Cross-sectional expansion between discharge throttle bore 8 and diffuser 9 forms a Carnot opening where the flow of the high pressure jet, from the outlet throttle bore 8 towards the center of the valve ball 3 is no longer laminar to the walls of the diffuser 9, rather, there are lossy flow vortices at the cross-sectional expansion forms.

Despite these flow losses, the diffuser 9 has in connection with the steep-walled valve seat 2 a much higher centering effect on the Valve ball 3 as the conventional flat conical valve seats in connection with an immediate transition from the drain throttle bore 8 to the Valve seat 2 using conventional technology.

Fig. 2 shows a cross section through the fuel injection valve in the area of the valve seat of the injection control valve in a second embodiment the invention. It can be clearly seen here that in this embodiment the cone angle α is much more acute than in the first embodiment according to Fig. 1. In this case the cone angle α = 60 ° and the length to diameter ratio of the diffuser 0.15.

The valve ball 3 plunges much deeper in this embodiment the diffuser 9 and floats when the injection control valve 30 is closed µm over the drain edge 14 of the drain throttle bore 8. Through this acute-angled cone of the valve seat 2, the valve ball 3 is hydraulic centered. This means that the closing can be done smoothly and No distortions in the return flow when closing the valve ball 3 occur. Thanks to the extremely short diffuser bore with a length-to-diameter ratio of 0.15 can from the outlet throttle bore 8 escaping high pressure jet the ball is not significantly outside of the Meet center line 15. This results in further reduced radial forces. The relatively large diffuser hole also has the advantage that the steep-walled valve seat 2 can be machined and polished better.

FIG. 3 shows a cross-section in sections in the area of the essential structural parts of a conventional injection control valve, as already described in detail in the prior art chapter.

Claims (8)

1. Fuel injection valve for high-pressure injection of fuel from a central high-pressure line (6) into combustion chambers of an internal combustion engine, the said fuel injection valve having an injection control valve (1) with a valve seat (2), a valve ball (3), and a guide element (4) guiding the valve ball (3), which guide element (4) presses the valve ball (3) on the valve seat (2) to close the said injection control valve and subjects the valve ball (3) to a spring prestressing of a spring (5) to open the said injection control valve, the valve ball (3) being lifted off the valve seat (2) in the open state by means of a high-pressure jet which is fed via an outlet restrictor bore (8) from a control space (7) connected to the central high-pressure line (6), a diffuser (9) being arranged between the valve seat (2) and outlet restrictor bore (8), characterized in that the outlet restrictor bore (8), the diffuser (9) and the valve seat (2) have approximately a steep-walled funnel shape with a right-angled to acute-angled cone angle (α).
2. Fuel injection valve according to Claim 1, characterized in that the minimum diameter (d) and maximum diameter (D) of the diffuser (9) are identical.
3. Fuel injection valve according to Claim 1 or 2, characterized in that the ratio between a mean diameter d_m of the diffuser (9) and a diameter (m) of the outlet restrictor bore (8) is between 1.2 and 2.
4. Fuel injection valve according to one of Claims 1 to 3, characterized in that the cone angle (•) is 60 to 90°.
5. Fuel injection valve according to one of Claims 1 to 4, characterized in that between 1/5 and 1/10 of the radius (r) of the valve ball (3) enters into the diffuser (9).
6. Fuel injection valve according to one of Claims 1 to 5, characterized in that the maximum diameter (D) of the diffuser (9) and the length of the diffuser (9) are matched to one another in such a way that, if the injection valve (1) is closed, the valve ball (3) is positioned at a distance of ≤ 0.1 mm, preferably between 30 and 80 µm, above the outlet restrictor bore (8).
7. Fuel injection valve according to one of Claims 1 to 6, characterized in that the outlet restrictor bore has a length-to-diameter ratio between 1 and 20.
8. Fuel injection valve according to one of Claims 1 to 7, characterized in that the diffuser (9) has a length-to-maximum-diameter ratio between 0.1 and 0.5.

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