EP3822475B1 - Valve for metering a fluid - Google Patents

Description

State of the art

The invention relates to a valve for metering a fluid, in particular a fuel injection valve for internal combustion engines. In particular, the invention relates to the field of injectors for fuel injection systems in motor vehicles, in which fuel is preferably injected directly into the combustion chambers of an internal combustion engine.

From the DE 10 2013 222 613 A1 a valve for metering fluid is known. The known valve has an electromagnet for actuating a valve needle that controls an orifice. The electromagnet is used to actuate an armature that can be moved on a valve needle. Here, the armature has a bore adjacent to the valve needle, which forms a spring mount for a pre-stroke spring. This configuration has the disadvantage that guidance between the armature and the valve needle is realized only over a short guidance length.

From the EP2789844 A1 discloses a valve for metering a fluid with an electromagnetic actuator and a valve needle that can be actuated by the actuator, with an armature of the actuator being guided on the valve needle, with a stop element being arranged on the valve needle, which limits a movement of the armature relative to the valve needle .

Disclosure of Invention

The valve according to the invention with the features of claim 1 has the advantage that an improved design and mode of operation are made possible. In particular, improved guidance between the armature and the valve needle and the valve needle along a longitudinal axis of the housing can be implemented. The design of the stop element according to the invention has the advantage that an advantageous flow of fuel in the area of the Stop element can be achieved without the inner bore of the inner pole must be increased.

Advantageous further developments of the valve specified in claim 1 are possible as a result of the measures listed in the dependent claims.

In the valve for metering the fluid, the armature that serves as the magnet armature is not firmly connected to the valve needle, but is mounted in a cantilevered manner between stops. Such a stop can be formed on a stop element, which can be realized as a stop sleeve and/or a stop ring. In the resting state, the armature is adjusted by a spring to a stop that is stationary with respect to the valve needle, so that the armature rests there. When the valve is actuated, the entire free travel of the armature is then available as an acceleration path, with the spring being shortened during acceleration. The armature free travel can be specified via the axial play between the armature and the two stops.

It is advantageous that the guide length between the armature and the valve needle is increased. For example, the armature can be guided on its outside in the valve housing along the longitudinal axis. The guidance of the valve needle along the longitudinal axis then improves accordingly due to the increased guidance length between the armature and the valve needle. In a configuration in which the valve needle is guided via the stop element, for example on an inner pole arranged in a stationary manner in the housing, the result is correspondingly improved guidance of the armature relative to the housing.

It is advantageous that the spring can immerse itself completely in the spring receptacle when it is actuated, so that an optimal compromise can be achieved in relation to several disadvantages of a conventional design.

The disadvantages of a conventional design relate firstly to manufacturability, costs and assembly if a design without a spring mount is implemented, in which an additional component is required to accommodate the spring and connect it to the armature. Second Disadvantages arise when a pole face between the armature and the inner pole is reduced, since a lower magnetic force then occurs. This relates in particular to a possible configuration in which a stepped bore is designed on the inner pole in order to create space for a spring.

A third disadvantage relates to a magnetic short circuit across the spring and the associated loss of magnetic force, which results in slower force build-up and lower holding force in the open state. This usually affects the magnetic spring steel used, which represents a bypass for the magnetic flux between the armature and the inner pole. A fourth disadvantage relates to the smaller contact surface between the armature and a stop ring in a variant in which the stop ring dips into the spring seat formed on the armature. This can cause increased wear and reduced hydraulic damping.

A fifth disadvantage may result in a lever arm between the upper needle guide and the armature, particularly in the above embodiment where the stop ring dips into the spring retainer. This can result in large needle deflection, leading to increased wear, skewing, and the like. A sixth potential disadvantage relates to designs that require a large spring diameter. Due to the limited radial installation space, lower spring forces can then be realized, which is bad for rapid armature settling after the first injection, in particular with regard to multiple injections. With the same spring force, a larger spring diameter also means a larger tilting moment on the armature, which is also disadvantageous for the injector function and, in particular, can result in a tilted armature stop. A seventh and last disadvantage relates to the risk of the spring bulging under load and the resulting contact with the inner pole and/or the stop ring due to a relatively long spring length and small radial space conditions. This leads to undefined friction, which, in addition to possible wear and the formation of particles, results in considerable scattering of the injection behavior.

Thus, by completely immersing the spring in the spring seat of the armature, an optimal compromise can be achieved in relation to the possible disadvantages listed above. In this case, the stop element can be made of a non-magnetic material, as a result of which it can separate the inner pole from the armature from a magnetic point of view. Furthermore, the lever arm can be kept short. Both a pole face and a stop face between the armature and the stop element, in particular the stop ring, can be selected to be sufficiently large. Furthermore, a relatively small inner diameter of the spring can be realized, so that relatively high spring forces can be achieved even with a comparatively thin wire thickness of the spring. Furthermore, the spring can also be designed to be relatively short, so that the risk of buckling and wear that occurs accordingly is reduced and a tilting moment introduced in this regard on the armature remains within acceptable limits.

An advantageous flow through the armature is made possible. As a result, in one possible embodiment, the armature can be guided in the housing. Furthermore, in a further possible configuration, an annular gap between the armature and the housing can be minimized. In relation to the specified housing dimensions, this results in a rapid build-up of force and a large holding force. Due to the intersection of the through-openings with the spring receptacle, the end face of the armature facing the inner pole can also be made larger than if separate through-openings are realized.

A further advantage is that the flow cross section can be increased disproportionately to the resulting reduction in the surface area of the end face of the armature.

Brief description of the drawings

• Fig. 1 ein Ventil in einer auszugsweisen, schematischen Schnittdarstellung entsprechend einem ersten Ausführungsbeispiel;
• Fig. 2 ein Ventil in einer auszugsweisen, schematischen Schnittdarstellung entsprechend einem zweiten nicht erfindungsgemäßen Beispiel;
• Fig. 3 und 4 mögliche Ausgestaltungen eines Ankers eines Ventils aus der in Fig. 1 mit III bezeichneten Blickrichtung und
• Fig. 5 bis 8 mögliche Ausgestaltungen eines Anschlagelements eines Ventils entgegen der in Fig. 1 mit III bezeichneten Blickrichtung.

Preferred embodiments of the invention are in the following description with reference to the accompanying drawings in which Corresponding elements are provided with the same reference numerals, explained in more detail. Show it:

• 1 a valve in a partial, schematic sectional view according to a first embodiment;
• 2 a valve in a partial, schematic sectional view according to a second example not according to the invention;
• Figures 3 and 4 possible configurations of an armature of a valve from the in 1 line of sight indicated by III and
• Figures 5 to 8 possible configurations of a stop element of a valve contrary to the in 1 line of sight marked III.

Embodiments of the invention

1 shows a valve 1 for metering a fluid in a partial, schematic sectional view according to a first embodiment. The valve 1 can be embodied in particular as a fuel injection valve 1 . A preferred application is a fuel injection system in which such fuel injectors 1 are designed as high-pressure injectors 1 and are used for direct injection of fuel into associated combustion chambers of the internal combustion engine. Liquid or gaseous fuels can be used as the fuel. Accordingly, the valve 1 is suitable for metering liquid or gaseous fluids.

The valve 1 has a housing (valve housing) 2 in which an inner pole 3 is arranged in a stationary manner. A longitudinal axis 4 is defined by the housing 2 and serves as a reference for guiding a valve needle 5 arranged within the housing 2 . This means that the valve needle 5 should be aligned along the longitudinal axis 4 during operation.

An armature (magnetic armature) 6 is arranged on the valve needle 5 . A stop element 7 and a further stop element 8 are also arranged on the valve needle 5 . At the stop elements 7, 8 stops 7 ', 8' are formed. In this case, the armature 6 can be moved between the stop elements 7, 8 when it is actuated, with an armature free path 9 being predetermined. The armature 6, the inner pole 3 and a magnet coil (not shown) are components of an electromagnetic actuator 10.

A valve closing body 11 is formed on the valve needle 5 and interacts with a valve seat surface 12 to form a sealing seat. When the armature 6 is actuated, it is accelerated in the direction of the inner pole 3 . If the armature 6 hits the stop 7' of the stop element 7 and thereby actuates the valve needle 5, then fuel can be injected via the opened sealing seat and at least one nozzle opening 13 into a space, in particular a combustion chamber.

The valve 1 has a restoring spring 14, which moves the valve needle 5 via the stop element 7 into its initial position, in which the sealing seat is closed.

The armature 6 is based on a cylindrical basic shape 20 with a through hole 21 , the armature 6 being guided on the through hole 21 on the valve needle 5 . Here, the basic shape 20 of the armature 6 has a length L between an end face 22 facing the inner pole 3 and an end face 23 facing away from the inner pole 3 .

The armature 6 has a spring mount 25 . The spring seat 25 is open on the end face 22 of the armature 6 . The spring receptacle 25 has a length f along the longitudinal axis 4 between the end face 22 and a spring support surface 26 of the armature 6 . The spring support surface 26 here represents the base 26 of the spring receptacle 25. In the initial state, in which the sealing seat is closed, a spring 27 partially arranged in the spring receptacle 25 has a spring length F. The spring length F is here the spring length F of the spring 27 in the non-actuated initial state. The spring 27 supports this on the one hand on the spring support surface 26 of the armature 6 and on the other hand on the stop 7 'of the stop 7 from. The spring length F is greater than the length f of the spring receptacle 25. However, when the armature 6 is actuated, the spring 27 is shortened compared to its initial length F, and it can dip completely into the spring receptacle 25.

In this exemplary embodiment, a guide web 28 is formed on the armature 6 . The armature 6 has a (shortened) length l along the longitudinal axis 4 between the spring support surface 26 and the end face 23 . Without the guide web 28, only this shortened length l would be available as a guide length. The guide bar 28 lengthens the length l by the length s of the guide bar 28 along the longitudinal axis 4 . This results in the guide length l+s in this exemplary embodiment. In this case, the length s of the guide bar 28 is preferably chosen to be the same as or even greater than the length f of the spring receptacle 25 . As a result, the guide length l + s of the armature 6 on the valve needle 5 is equal to or even greater than the length L of the armature 6 between its end faces 22, 23.

In this exemplary embodiment, the valve needle 5 is guided with respect to the longitudinal axis 4 or with respect to the housing 2 via the stop element 7 . Possible configurations of the stop element 7, which allow an advantageous passage of the fluid, in particular fuel, are based on the Figures 5 to 8 described. In this exemplary embodiment, there is an annular gap 34 between an outer side 32 of the armature 6 and an inner side 33 of the housing 2.

In a modified embodiment, the valve needle 5 can additionally or alternatively also be guided via the armature 6 . The outside 32 of the armature 6 extends at least partially to the inside 33 of the housing 2. In this embodiment, instead of the guide area 30, an annular gap can then be realized between the stop element 7 and the inner pole 3.

Advantageous guidance of the valve needle 5 along the longitudinal axis 4 can thus be implemented. At the same time, this results in an advantageous guidance between the armature 6 and the valve needle 5 over a guidance length l+s, which is preferably not less than the length L.

2 shows a valve 1 in a partial, schematic sectional view corresponding to a second example not according to the invention. In this example, a guide extension 40 is provided. The guide extension 40 has a length s' along the longitudinal axis 4, by which the guide of the armature 6 on the valve needle 5 is extended. This means that in this example the guide length s′+l is realized along the longitudinal axis 4 between the armature 6 and the valve needle 5 .

It is thus possible in this example for the spring receptacle 25 to be directly adjacent to the valve needle 5 . In particular, this facilitates the manufacture of the armature 6 since the spring receptacle 25 can be realized by a cylindrical recess aligned with the longitudinal axis 4 . As a result, however, directly on the basic form 20 of the armature 6 only the length l which is shortened compared to the length L of the armature 6 between the end faces 22, 23 is available. As a result, this shortened length l is lengthened by the length s′ via the guide extension 40 . In particular, the length s′ can be predetermined in such a way that the guide length s′+l is equal to or even greater than the length L of the armature 6 between its end faces 22 , 23 .

In addition, the guide extension 40 is designed in the form of a sleeve. This means that an outer diameter 41 on the guide extension 40 is selected to be significantly smaller than an outer diameter 42 on the outside 32 of the armature 6.

Furthermore, the spring 27 is designed with ground spring ends 43, 44 in this example. This results in an even better edition. Furthermore, there is reduced wear and a more uniform introduction of force into the armature 6 on the spring support surface 26 on the one hand and on the stop 7′ of the stop element 7 on the other.

Figures 3 and 4 show possible configurations of the armature 6 of the valve 1 from FIG 1 III designated viewing direction, for better understanding, the valve needle 5 is shown as a sectional area. The end face 22 is divided into sub-areas 22A and 22B, between which the spring receptacle 25 is provided. Furthermore, through openings 51 to 54 are provided, which in this exemplary embodiment are configured as through bores 51 to 54 with a circular cross section. This results in intersections between the through bores 51 to 54 and the spring mount 25. This means that the fuel can flow over the length f of the spring mount both through the part of the spring mount 25 not filled by the spring 27 and through the through openings 51 to 54 . The fuel then flows over the shortened length l only through the through openings 51 to 54. This enables a fuel flow from the end face 22 to the end face 23 with little throttling, without the total area of the end face 22, which consists of the partial areas 22A, 22B composed, is further reduced. This has a favorable effect on the control behavior when the armature 6 is actuated, since both a large magnetic force and reduced hydraulic throttling result.

In the case of the 4 In the exemplary embodiment described, kidney-shaped configurations of the through-openings 51 to 54 are also implemented, so that the through-openings 51 to 54 extend in a circumferential direction 55 around the longitudinal axis 4 or circumferentially around the longitudinal axis 4 over a larger angular range. As a result, the flow of fuel over the shortened length l of the armature 6 is improved in particular.

Figures 5 to 8 show possible configurations of the stop element 7 of the valve 1 contrary to the 1 View direction denoted by III, the valve needle 5 being shown in section for illustration purposes. Here, a support area 60 for the spring 27 is specified. The support area 60 is delimited radially outwards by a broken line 60A. Furthermore, the support area 60 is delimited radially inwards by a line 601 shown as a broken line. The support area 60 serves as the structurally predetermined support area 60 in which the selected spring 27 is to be supported. Furthermore, the Configurations preferably for an application in which a guide between the stop element 7 and the inner pole 3 is realized, as is the case, for example, in FIG 1 is illustrated.

Indentations 61 to 64 are provided in order to direct the fuel past the stop element 7 . Here, the stop element 7 can be modified by such indentations 61 to 64, starting from a basic hollow-cylindrical shape 65, which is characterized by an outer diameter D. This results in both the possibility of a guide on the outer diameter D and a fuel passage through the depressions 61 to 64.

The depressions 61 to 64 are designed here in such a way that, viewed from the longitudinal axis 4, they reach a maximum of a diameter d. This means that an annular surface 66 remains from the valve needle 5 to the diameter d.

Preferably, the diameter d is set to be between the outer line 60A and the inner line 60l. As a result, the spring 27 also rests at least partially on the support area 60 in the area of the depressions 61 to 64, namely at least on the annular surface 66. This results in a compromise between a good contact of the spring 27 on the support area 60 and the largest possible depressions 61 to 64 and at the same time the possibility of guiding on the outer diameter D.

The Figures 5 to 8 show different ways to perform the depressions 61 to 64. figure 5 as an intersection with cylinder bores, 6 as intersections with rectangular cutouts, 7 as an intersection with flattening. When designing 8 the flow cross section can be formed by ring segments.

Claims (4)

1. Valve (1) for metering in a fluid, in particular fuel injection valve for internal combustion engines, with an electromagnetic actuator (10) and a valve needle (5) which can be actuated by the actuator (10), an armature (6) of the actuator (10) being guided on the valve needle (5), a stop element (7) which limits a movement of the armature (6) relative to the valve needle (5) being arranged on the valve needle (5), and the armature (6) having a spring support (25) which is open towards the stop element (7) and into which a spring (27) which is supported on the stop element (7) is inserted, the valve needle (5) being guided via the armature (6) and/or the stop element (7) along the longitudinal axis (4) of a housing (2), and a length (f) of the spring support (25) as viewed along the longitudinal axis (4) being smaller than a spring length (F) of the spring (27) in the non-actuated starting state, characterized in that the stop element (7) is based on a hollow-cylindrical basic shape with a defined external diameter (D) with regard to the longitudinal axis (4), and in that at least one depression (61-64) is configured up to a defined diameter (d) with regard to the longitudinal axis on an outer side of the basic shape (65), and in that the supporting region (60) for the spring (27) lies within the defined external diameter (D) of the stop element (7) and outside the defined diameter (d) of the stop element (7), a guide web (28) which faces the stop element (7) and guides the armature (6) along the longitudinal axis (4) on the valve needle (5) being configured on the armature (6).
2. Valve according to Claim 1, characterized in that, in the case of actuation, the spring (27) can be shortened to that length (f) of the spring support (25) which is predefined by the spring support (25) of the armature (6) .
3. Valve according to either of Claims 1 and 2, characterized in that the armature (6) has at least one through opening (51-54) which extends along the longitudinal axis (4) and intersects with the spring support (25).
4. Valve according to Claim 3, characterized in that at least one through opening (51-54) is configured to be of kidney-shaped extent in the circumferential direction (55) .

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