EP2932087B1 - Fuel injection valve - Google Patents

Description

The invention relates to a fuel injection valve, as it is preferably used for injection of fuel in combustion chambers of internal combustion engines.

State of the art

Fuel injection valves, as they are preferably used to inject fuel under high pressure into combustion chambers of internal combustion engines, are known from the prior art, for example from the published patent application DE 198 27 267 A1 and EP2019198 A2 , The fuel injection valves comprise a nozzle needle which cooperates with a nozzle seat for opening and closing at least one injection opening. The nozzle needle is thereby moved directly or indirectly by the pressure in a control chamber in the longitudinal direction and thus opens and closes the injection openings, wherein the control chamber via a control valve with a low pressure space is connectable. The control valve comprises an electrically controllable actuator which actuates a control valve member which opens and closes a drainage bore connecting the control chamber to the low pressure space. The prior art fuel injector has a control valve member that includes a sealing ball that cooperates with a control valve seat to open and close the drain hole. The sealing ball acts together with a conical control valve seat, so that between the control valve seat and the sealing ball a flow cross-section is controlled, through which the fuel flows from the drain hole in the low-pressure chamber.

In particular, when using the fuel injection valve in a high-speed, self-igniting internal combustion engine, it is essential that the injection is very precise, d. H. at a specific time and with the exact duration. For a quiet and low-emission combustion, moreover, the injection is often divided into two or more partial injections, which is achieved by correspondingly fast opening and closing of the control valve. To relieve the control room as quickly as possible and refill with fuel under high pressure after closing the control valve, the control valve must release the drain hole as soon as possible and close again, which is possible the faster the smaller the stroke, the Pass control valve member, since the length of the stroke is received directly in the switching time. In addition, the forces necessary to move the control valve member should be kept as low as possible because the structure is e.g. a strong magnetic force requires high currents, which can be switched only relatively slowly.

To aufzusteuern the largest possible cross section with the least possible stroke, it is thus advantageous if the sealing ball has the largest possible diameter, and the sealing line on which the control valve member, so here the sealing ball rests on the control valve seat, has the largest possible diameter. During the movement of the control valve member away from the control valve member, a large flow cross-section is already opened at low lift. However, if the diameter is made large, the control valve member will be exposed to a high opening force by the high fuel pressure from the side of the control space which pushes the control valve member away from the control valve seat. To compensate for this force, a correspondingly strong, the control valve member loading spring must be provided, which in turn must be suppressed by a very strong electromagnet or piezoelectric actuator, which requires high currents and thus high energy and has a negative effect on the switching time of the control valve. The sealing line on which the control valve member is seated on the valve seat and which limits the pressurized surface of the control valve member to the outside, thus can not be chosen too large, so that an acceleration of the switching time are set narrow limits.

Advantages of the invention

The fuel injection valve according to the invention has the advantage that the switching time compared to the known control valves is significantly reduced without the required forces are increased to move the control valve member. For this purpose, the fuel injection valve has a control valve which controls the flow of fuel through a drainage bore connecting the control chamber to a low pressure space, the control valve comprising a movable sealing member which cooperates with a control valve seat and closes or opens a drainage bore, the seal happens along a boundary length. The boundary length encloses a cross-sectional area, and the relationship is that the quotient of the square of the boundary length and the cross-sectional area is greater than 4 · π. This ratio is always met at an outlet opening of a drain hole when the outlet opening is not circular. The larger the boundary length in relation to the enclosed cross-sectional area, the larger the controlled flow cross-section through which the fuel can flow from the drain hole into the low-pressure space. Thus, a small stroke of the control valve member is sufficient to control a sufficient flow area and to allow the fuel drain from the control chamber, which reduces the switching time of the control valve.

Alternatively it can also be provided that instead of a drain hole with a corresponding outlet opening a plurality of drain holes are provided, all of which open into the low-pressure chamber and are all closed by the control valve member in contact with the control valve seat. Here, the quotient of the sum of the squares of the boundary lengths of the respective outlet openings and the sum of the cross-sectional areas of the individual drain holes must be greater than 4 · π. The effect here is the same as in the provision of a non-circular outlet opening of the drain hole, namely, that the controlled flow cross-section is greater than when the same flow cross-section is formed by a single circular drain opening.

In a first advantageous embodiment, whether a single drain hole is provided or more drain holes are provided, the Control valve seat formed flat, which is easy to manufacture, even if several drain holes are provided. The sealing element, which cooperates with its sealing surface with the control valve seat, is also formed flat in an advantageous manner. The Berandungslängen the individual drain holes or the outlet openings are identical in this case with the outlet openings in the control valve seat and can be easily and inexpensively.

In a further advantageous embodiment, a plurality of drain holes are provided, and their outlet openings in the control valve seat are arranged in a circle around a center. The outflow of fuel from the drain holes can be done in this case, both inward and outward, so that a particularly large flow area is achieved.

The drain hole or the drain holes are advantageously formed so that they have a throttle function, which are necessary for the operation of the respective fuel injection valve. By this appropriate configuration can be achieved that the drain hole no longer has to have a separate throttle, as in other fuel injection valves, which facilitates the production.

drawing

Figur 1

einen Längsschnitt durch ein Kraftstoffeinspritzventil in schematischer Darstellung, wie es aus dem Stand der Technik bekannt ist,

Figur 2

eine Vergrößerung im Bereich des Steuerventilsitzes des bekannten Kraftstoffeinspritzventils,

Figur 3

das Ventilstück mit zugehörigem Dichtelement einer ersten Ausführungsform des erfindungsgemäßen Kraftstoffeinspritzventils, die

Figur 3a

zeigt eine Draufsicht auf das Ventilstück und

Figur 3b

einen weiteren Querschnitt durch das Ventilstück im Bereich des Steuerventilsitzes in einer gegenüber der Figur 3 um 90 Grad gedrehten Darstellung,

Figur 4

einen Querschnitt durch das Ventilstück eines weiteren erfindungsgemäßen Kraftstoffeinspritzventils und

Figur 4a

eine Draufsicht auf dieses Ventilstück, und

Figur 5

in derselben Darstellung wie Figur 4 ein weiteres Ausführungsbeispiel der Erfindung.

In the drawing, various embodiments of the fuel injection valve according to the invention are shown. It shows

FIG. 1

a longitudinal section through a fuel injection valve in a schematic representation, as is known in the prior art,

FIG. 2

an enlargement in the region of the control valve seat of the known fuel injection valve,

FIG. 3

the valve piece with associated sealing element of a first embodiment of the fuel injection valve according to the invention, the

FIG. 3a

shows a plan view of the valve piece and

FIG. 3b

a further cross section through the valve piece in the region of the control valve seat in a relation to the FIG. 3 rotated by 90 degrees,

FIG. 4

a cross section through the valve piece of another fuel injection valve according to the invention and

FIG. 4a

a plan view of this valve piece, and

FIG. 5

in the same representation as FIG. 4 a further embodiment of the invention.

Description of the embodiments

In FIG. 1 a fuel injection valve known from the prior art is shown schematically in longitudinal section. The fuel injection valve has a housing 1, which comprises a holding body 2 and a nozzle body 3, which are clamped liquid-tight against each other by a tensioning device, not shown in the drawing. In the housing 1, a pressure chamber 5 is formed, which is connected via a high-pressure line 12 to a high-pressure accumulator 13 and is always filled with fuel under high pressure during operation of the fuel injection valve. The high pressure accumulator 13 is in turn supplied via a high pressure pump 14 with compressed fuel, which sucks the high pressure pump 14 from a tank 15 via a line 16.

In the pressure chamber 5, a piston-shaped nozzle needle 6 is arranged longitudinally displaceable, which is guided in a guide portion 106 in the nozzle body 3. The fuel flow through the pressure chamber 5 in the region of the guide section 106 is ensured by a plurality of polished sections 18 on the nozzle needle 6. The nozzle needle 6 has at its combustion chamber end, a sealing surface 19, with which it cooperates with a nozzle seat 20 which has a conical shape in this embodiment and in which a plurality of injection openings 22 are formed, which are closed by the nozzle needle 8, if in Attachment to the nozzle seat 20 is. Facing away from the nozzle seat 20, the nozzle needle 6 is guided in the bore 8 of a valve piece 7, which closes the pressure chamber 5 away from the valve seat. The valve member 7 is in turn fixed by an intermediate body 9 by a closing plate 4 which is screwed into the holding body 3, fixed within the housing 1. The valve member 7 also separates the pressure chamber 5 from a low pressure chamber 29, in which a control valve 10 is arranged and which is connected via a drain line 37 to the fuel tank 15 and thereby always maintained at low pressure.

Through the nozzle needle 6 and the bore 8 in the valve piece 7, a control chamber 25 is limited, which is connected via an inlet bore 27 which is formed in the valve member 7 with the pressure chamber 5. In the valve piece 7, a drain hole 28 is also provided, which connects the control chamber 25 with the low-pressure chamber 29. The drain hole 28 in this case has an outlet throttle 128, which is formed within the drain hole 28, so that the flow of fuel is only throttled by the drain hole. The drain hole 28 opens into a control valve seat 33, which is formed on the valve piece 7 and has a conical shape, and forms there an outlet opening 228, as shown in more detail in FIG. 2 is shown.

To open and close the drain hole 28, the control valve 29, which includes a magnet armature 30, to which a sealing ball 32 is fixed, which cooperates with the conical control valve seat 33. The armature 30 is acted upon by a spring 35 in the direction of the control valve seat 33 with a closing force and can be moved by means of an electromagnet 31 against the force of the spring 35 so that the sealing ball 32, the outlet opening 228 of the drain hole 28 releases. Since the drain hole 28 is formed rotationally symmetrical, the outlet opening 228 forms a circle on which the sealing ball 32 bears sealingly when it is in the closed position in contact with the control valve seat 33.

The operation of the fuel injection valve as follows: At the beginning of the injection, the control valve 10 is closed, so that in the control chamber 25, the same high fuel pressure prevails as in the pressure chamber 5, which presses the nozzle needle 6 against the nozzle seat 20 and thus closes the injection openings 22. If an injection takes place, then the electromagnet 31 is energized and attracts the armature 30 against the force of the spring 35. The sealing ball 32 thus lifts off from the control valve seat 33 and releases the outlet opening 228 of the drain hole 28. The outflowing fuel from the control chamber 25 can drop the fuel pressure in the control chamber 25, although constantly fuel flows through the inlet bore 27, but this inflow is less than the outflow through the drain hole 28. The thus reduced hydraulic force on the nozzle seat facing away from the end of the nozzle needle 6 causes the Nozzle needle 6 is pushed away from the nozzle seat 20 by the fuel pressure in the pressure chamber 5, so that the injection openings 22 are connected to the pressure chamber 5 and fuel exits from the injection openings 22. To end the injection, the energization of the electromagnet 31 is stopped, whereupon the spring 35 presses the armature 30 and thus also the sealing ball 32 back into its closed position. About the influx of fuel through the inlet bore 27 is again very quickly a high fuel pressure in the control chamber 25, which presses the nozzle needle 6 back into its closed position in contact with the nozzle seat 20.

FIG. 3 shows the valve piece 7 of a fuel injection valve according to the invention, in which compared to the in FIG. 1 shown fuel injection valve only the valve piece 7 and cooperating with the control valve seat 33 formed thereon sealing member 40 have been changed. The valve member 7 is here constructed in two parts and, in addition to the actual valve piece 7, which receives the nozzle needle 6, still a valve section 7 ', in which the outlet throttle 128 is formed here. The control valve seat 33 is in contrast to that in FIG FIG. 1 shown embodiment designed as a flat seat, in which the outlet opening 228 of the drain hole 28 is arranged centrally. At the magnet armature 30, a sealing element is provided here for cooperation with the control valve seat 33, which has a hemispherical shape, wherein the flat side of the hemisphere faces the control valve seat 33. The outlet opening 228 of the drain hole 28 is rectangular in this embodiment, as shown in FIG FIG. 3a in a plan view of the valve section 7 'is shown. The rectangular outlet opening 228 has a length a and a width b , because the rectangular outlet opening 228 is completely covered by the sealing element 40 in the closed position of the control valve and thereby sealed. Since both the control valve seat 33 and the sealing element 40 are formed flat, the outlet opening 228 is sealed exactly along the contour of this rectangle, so that the boundary length U of the outlet opening 228 is twice ( a + b ): $$U=2\cdot \left(a+b\right)$$

The cross-sectional area A enclosed by the boundary length U is thus a · b : $$A=a\cdot b$$

It can easily be shown that for all values a , b the quotient of the square of the boundary length U ² and the cross-sectional area A is greater than 4 · π: $$\frac{U^2}{A}>4\pi \mathrm{,}$$

The longer the outlet opening 228 is in this exemplary embodiment, ie, the smaller b in relation to a, the larger the controlled outflow cross section of the control valve for a given cross-sectional area A of the outlet opening 228.

In FIG. 3b the portion of the drain hole 28 is shown in cross-section, which is formed in the valve portion 7 ', wherein the representation relative to the in FIG. 3 turned 90 degrees. The drain hole in this illustration shows a funnel shape, which forms the transition from the cylindrical drain hole 28 within the valve piece 7 to the rectangular outlet opening 228 on the control valve seat 33. In how many parts the valve piece 7 is divided depends on the shape of the drain hole 28 and the available manufacturing process. It can also be provided that the valve member 7 shown here and the valve section 7 'are integrally formed.

The outflow of the fuel within the drain hole 28 is turbulent in a fuel injection valve, that is, the influence of the surface of the drain hole 28 is of minor importance for a given cross-sectional area. The fuel thus flows via the drainage bore 28 with approximately the same resistance as a circular drainage bore having the same cross-sectional area. Thus, it is not necessary to compensate for the influence of the larger surface of the drain hole 28 compared to the known rotationally symmetrical drain holes by an adapted cross-sectional area.

In FIG. 4 is a further embodiment of the fuel injection valve according to the invention shown, in which case only the valve section 7 'is shown in cross section. Instead of a single drain hole here a plurality of drain holes 28 'is provided, which open into the control valve seat 33.

As FIG. 4a in a plan view of the valve section 7 ', the drain holes 28' and their outlet openings 228 'are arranged in a circle around the center of the valve section 7'. Each of these outlet openings 228 ', analogous to the embodiment of the FIG. 3 a boundary length U _i and a cross-sectional area A _i . Accordingly, the relationship applies here that the quotient of the sum of the squares of the boundary lengths U _i and the sum of the cross-sectional areas A _{i of} the individual drain holes 28 'is greater than 4 · π: $$\frac{{\Sigma }_i{\mathrm{<figure-callout\; id="2"\; label="U\; i"\; filenames="imgf0001.png"\; state="\{\{state\}\}">U\; </figure-callout>}}_i^{}}{{\Sigma }_i{A}_i}>4\pi$$

That is, equivalently, at least one exit opening is not circular. The outflow of fuel from the outlet openings 228 'takes place in all possible directions practically over the entire boundary length U _i , so that even with only a small stroke of the sealing element 40, a high outflow cross section is opened. Unlike the in FIG. 3 shown embodiment, the sealing element 40 'here have an annular disk-shaped surface, since so the tread surface on the control valve seat 33 is reduced, which increases surface pressure and thus improves the sealing function. The drain holes 28 'of the embodiment of FIG. 4 can also be designed so that they take over the necessary for the function of the fuel injection valve throttle function, that is, that a separate outlet throttle, as for example in FIG. 3 is shown, can be omitted.

In FIG. 5 is shown a further embodiment, this embodiment of the in the FIG. 3 only differs in that an annular groove 44 is provided in the control valve seat 33. This annular groove 44 limits the effective control valve seat on which the sealing element 40 is seated, which improves the sealing function. In addition, the outflowing fuel, which is indicated by arrows, can be set in turbulence and thereby braked, so that a throttling function is provided by the annular groove 44, which can replace the function of the outlet throttle, so that a separate outlet throttle within the drain hole 28 is not necessary ,

The annular groove 44 can also be fluidically connected to the low-pressure side, that is, to the low-pressure space 29, for example, by a radial direction This prevents the control valve seat 33 is undermined by the inevitable wear with pressure and the acted upon by high pressure from the drain hole 28 surface of the sealing element 40 too strong elevated. The hydraulic opening force on the sealing element 40 or the armature 30 can thus always be kept below a limit, for example, below the spring force with which the magnet armature 30 is pressed by the spring 35 against the control valve seat 33. This ensures the tightness of the control valve 29 over the entire life.

In contrast to the embodiments previously shown, it can also be provided that the control valve seat 33 is not flat, but for example, has a slight conical shape, which cooperates with a corresponding conical sealing element. This allows a centering function of the sealing element with respect to the control valve seat 33, so that a part of the guide function for the armature 30 is thereby adopted.

Claims (8)

1. Fuel injection valve having a control valve (10) for controlling a fuel flow through a discharge bore (28) through which fuel is discharged from a control space (10) into a low pressure space (29) and which discharge bore (28) opens into a control valve seat (33) and forms there an outlet opening (228), wherein the control valve (10) comprises a movable sealing element (40) which interacts with the control valve seat (33; 33') and which when it bears on the control valve seat (33; 33') closes the outlet opening (228) of the discharge bore (28),
   characterized in that,
   in the closed state of the control valve (10) the sealing element (40) closes off the discharge bore (28) along a boundary length (U) with respect to the low pressure space (29) and the boundary length (U) surrounds a cross-sectional area (A) wherein the quotient of the square of the boundary length (U²) and the cross-sectional area (A) is greater than 4·π.
2. Fuel injection valve having a control valve (10) for controlling a fuel flow through a plurality of discharge bores (28') through which fuel is discharged from a control space (10) into a low pressure space (29), which discharge bores (28') open into a control valve seat (33) and form there outlet openings (228'), wherein the control valve (10) comprises a movable sealing element (40) which interacts with the control valve seat (33; 33') and which when it bears on the control valve seat (33; 33') closes the outlet openings (228') of the discharge bores (28'),
   characterized in that,
   the sealing element (40) closes off each of the outlet openings (228') of the plurality of discharge bores (28') along a boundary length (Ui) with respect to the low pressure space (29), and each boundary length (U_i) encloses in each case a cross-sectional area (A_i) wherein the quotient of the sum of the squares of the individual boundary lengths (U_i ²) and the sum of the individual cross-sectional areas (A_i) is greater than 4·π.
3. Fuel injection valve according to Claim 1 or 2, characterized in that the control valve seat (33) is of flat design.
4. Fuel injection valve according to Claim 3, characterized in that the sealing element (40) has a flat sealing face (41) with which it interacts with the control valve seat (33).
5. Fuel injection valve according to Claim 2, characterized in that the outlet openings (228') of the discharge bores (28') are arranged in a circular shape in the control valve seat (33).
6. Fuel injection valve according to Claim 1, characterized in that the discharge bore (28) has a rectangular outlet opening (228).
7. Fuel injection valve according to Claim 1, characterized in that the discharge bore (28) has an oval outlet opening (228).
8. Fuel injection valve according to Claim 1 or 2, characterized in that the discharge bore (28) or the discharge bores (28') are embodied in such a way that they have a throttle function which is necessary for the operation of the respective fuel injection valve.

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