EP3559438B1 - Fuel injector and use thereof - Google Patents

Description

State of the art

The invention relates to a fuel injector according to the preamble of claim 1. The invention also relates to the use of a fuel injector according to the invention.

A fuel injector with the features of the preamble of claim 1 is from EP 2 129 903 B1 known to the applicant. The known fuel injector has a magnet armature which is hat-shaped in cross section and which is used to control the outflow of fuel from a control chamber of a valve piece. The movement of an injection member (nozzle needle), which in turn is used to open or release at least one injection opening in the injector housing, is controlled in a known manner by blocking or releasing a drain hole in the valve piece connected to the control chamber. The known magnet armature has a through-hole into which a pin-shaped extension of the valve piece protrudes, the extension serving to support the magnet armature radially. Furthermore, the magnet armature in the area of its through-hole on the side facing the valve piece has a seat edge which, together with an inclined sealing surface running radially around a longitudinal axis of the valve piece, forms a sealing seat in the lowered position of the magnet armature, thereby preventing the drain to prevent fuel from leaving the control room. It is essential that the area of the radial guide surface of the valve piece for the magnet armature, which is formed on the extension, has the same radial distance in relation to the longitudinal axis as the sealing edge on the magnet armature. This has the consequence that the area of the valve piece, which is used for the radial mounting of the magnet armature, is exposed to the pressure of the control chamber and thus high or system pressure. Another fuel injector is from the EP 2 749 799 A1 known.

An essential criterion for the accuracy of the metering of the fuel quantity is the achievement of a specific stroke of the magnet armature or of the valve member closing the control chamber. The (maximum) armature stroke is dependent on the dimensioning and tolerance of various components, especially at the start of operation of a fuel injector, on the component temperatures. Components that are subjected to system or high pressure, especially in the area of the sealing of the drain hole from the control chamber, are exposed to greater heating than areas of components that are relatively far away from this area, since the fuel injector installed in the engine block is in the area of its Injector housing still has a relatively low temperature. The different degrees of heating of the components relevant for the armature stroke have the consequence that if the armature heats up or expands to a greater extent than the components surrounding the armature, the (maximum) armature stroke is shortened or less than in a state in which the for the armature stroke essential components have at least almost the same temperature. This has the consequence that - viewed over the operating time of the fuel injector - armature lifts of different heights are achieved with the same current supply to a magnet coil serving for the lifting movement of the magnet armature, the difference being a few micrometers. As a result, in conventional designs, the armature stroke must be increased by a so-called lead value to compensate for the temperature effects.

Disclosure of the invention

The fuel injector according to the invention with the features of claim 1 has the advantage that it always has at least almost the same armature stroke almost independently of the temperature, that is to say in particular also at the start of the start-up of the fuel injector. This is achieved according to the invention in that the sealing edge on the magnet armature (which serves to form a sealing seat with a sealing surface on the valve piece) has a smaller distance from the longitudinal axis of the magnet armature than the guide section on the magnet armature serving to guide the magnet armature. In other words, this means that the area of the radial guidance of the magnet armature is spaced relatively far from the sealing area, which is under system pressure. This has the consequence that the radial guidance of the armature on the valve piece is used Section of the armature heats up relatively slowly or almost simultaneously and by the same amount as the other components that radially surround the armature and exert an influence on the armature stroke. It is made possible for the components or sections relevant for the armature stroke to have the same axial length.

Advantageous developments of the fuel injector according to the invention are listed in the subclaims.

In addition to the knowledge that the change in length of the armature depends on the location of the radial guide of the armature in relation to its sealing edge, the invention makes use of the fact that the (temperature-dependent) linear expansion of the armature turns out to be smaller, the more compact or shorter the armature in Is formed in the direction of its longitudinal axis. Therefore, according to the invention, the magnet armature has a disk-shaped section extending radially around the longitudinal axis, on the outer circumference of which the guide section protruding in the direction of the valve piece is arranged, the inner wall of which interacts with a guide area on the valve piece. The magnet armature, which is approximately cup-shaped in cross section, can either be configured as a two-part magnet armature or as a one-piece magnet armature. When designed as a two-part magnet armature, the radially circumferential section in the form of a guide sleeve can optionally be made of an amagnetic material or metal. The connection between the guide sleeve and the central, disk-shaped section can in particular be made by a welded connection in the form of a laser weld seam. In contrast, a one-piece, i.e. monolithic, design of the magnet armature makes it possible to manufacture it as a sintered component, since this enables relatively inexpensive manufacture.

A preferred structural embodiment of the valve piece, which enables the possibility of an axially particularly short magnet armature and an axially relatively long valve piece in the guide area for the magnet armature, provides that the valve piece has at least one, preferably has a plurality of outflow bores arranged at equal angular distances from one another, which has / have an outlet in the area of the guide surface of the valve piece, the outlet connecting the outlet bore for the control chamber to a low-pressure area when the valve member is raised. The provision of several outflow bores arranged at equal angular distances from one another (having the same flow cross-section) has the advantage that, on the one hand, the throttle losses are minimized, since overall, a relatively large flow cross-section is available in the direction of the low-pressure area when the valve member or magnet armature is lifted, and On the other hand, no transverse or tilting forces are generated on the magnet armature, which simplifies or optimizes the guidance of the magnet armature.

In a structurally preferred development of such outflow bores, these are arranged at an inclined angle with respect to the longitudinal axis, such that the sealing surface on the extension of the valve piece is at a greater distance from the control chamber in relation to the longitudinal axis than the outlets of the outflow bores. In other words, this means that the outflow bores open out on the valve piece below the area of the sealing surface. As a result, a relatively long axial guide area on the magnet armature is achieved above with the sealing surface.

Another structurally preferred embodiment of the magnet armature, which makes it possible to position the sealing seat between the magnet armature and the valve piece more axially in the direction of the control chamber, provides that the magnet armature has a pin-shaped or sleeve-shaped protruding in the direction of the valve piece in a central area having the first extension, on whose end face facing the valve piece the sealing edge is formed, and that the first extension dips into a recess of the valve piece at least when the magnet armature is lowered.

Additionally or alternatively, a further structurally preferred embodiment of the magnet armature provides that it has in a central area a pin-shaped or sleeve-shaped second extension projecting in the direction of the magnet coil or magnet core, which axially into a through opening of a magnet core with little radial play immersed. Immersing the The second extension into the through-opening of the magnet core has the advantage that the relatively long axially guide reduces leakage losses that typically arise from an armature bolt axially penetrating the magnet armature.

In order, on the one hand, to maximize the axial guide length of the radially circumferential section on the armature in the area of the extension of the valve piece and to prevent the armature from jamming or tilting, and, on the other hand, to be able to make the extension relatively short in its axial length, it is provided that the at least one outlet of the outflow bore opens in the area of the magnet armature and that the magnet armature has at least one passage opening which is arranged in overlap with the outlet. To this end, it is additionally explained that in practice it makes sense to form a plurality of passage openings arranged at non-uniform angular distances from one another on the radially circumferential section of the magnet armature, these having a greater extent than that in a direction running transversely to the longitudinal axis, ie in the circumferential direction Outflow holes. This makes it possible that the magnet armature can rotate on the extension of the valve piece and, regardless of its angular position on the extension, for example, at least two outlets of outflow bores arranged on opposite sides can be depressurized via the passage openings on the magnet armature or fuel into the fuel via the passage openings Low pressure area can flow off.

Alternatively, however, to simplify the construction of the magnet armature, it is also conceivable that the outlet of the at least one outflow bore opens out on the side facing away from the magnet coil below the magnet armature.

Since the radially circumferential (flat) section of the magnet armature is arranged in the closed position at least almost in contact with the end face of the extension of the valve piece facing it, it is also advantageous if the magnet armature at least in the overlap area with the end face of the valve piece facing the magnet armature has at least one passage. The background to this is that it is desirable after the end of the current flow, ie to form the sealing seat between the Magnet armature and the valve piece to enable the fastest possible closing movement. However, this assumes that there is no fuel between the end face of the valve piece facing the disk-shaped section of the magnet armature and the disk-shaped section of the magnet armature, which would otherwise lead to hydraulic damping of the magnet armature closing movement. This attenuation can be prevented or reduced by the mentioned passage on the magnet armature. The number and size of the passages can be adapted to the desired damping behavior of the magnet armature.

Finally, the invention encompasses the use of a fuel injector according to the invention for compression-ignition internal combustion engines as described so far, the fuel injector being designed to work at a system pressure of more than 2000 bar.

Further advantages, features and details of the invention emerge from the description of preferred exemplary embodiments and with reference to the drawing.

Fig. 1

einen Teilbereich eines erfindungsgemäßen Kraftstoffinjektors in einem Längsschnitt,

Fig. 2

ein Ventilstück mit seinem damit zusammenwirkenden Magnetanker in einer perspektivischen Halbschnittdarstellung, wobei der Magnetanker eine kürzere axiale Längs aufweist als der bei dem Kraftstoffinjektor gemäß der Fig. 1 verwendete Magnetanker,

Fig. 3

ein Detail der Fig. 2 in einem Teillängsschnitt und

Fig. 4

einen modifizierten Magnetanker in einer perspektivischen Halbschnittdarstellung entsprechend der Fig. 2, wie er bei dem Kraftstoffinjektor gemäß der Fig. 1 verwendet wird.

This shows in:

Fig. 1

a partial area of a fuel injector according to the invention in a longitudinal section,

Fig. 2

a valve piece with its magnet armature interacting therewith in a perspective half-sectional view, the magnet armature having a shorter axial length than that of the fuel injector according to FIG Fig. 1 used magnet armature,

Fig. 3

a detail of the Fig. 2 in a partial longitudinal section and

Fig. 4

a modified armature in a perspective half-sectional view corresponding to FIG Fig. 2 , as in the fuel injector according to the Fig. 1 is used.

The same elements or elements with the same function are provided with the same reference numbers in the figures.

The fuel injector 100 shown in the figures is used to inject fuel into the combustion chamber, not shown, of a compression-ignition internal combustion engine. In particular, the fuel injector 100 is part of a so-called common rail injection system, which preferably has a system pressure of more than 2000 bar.

The fuel injector 100 has an injector housing 11 into which a pressure port 12 can be screwed. The pressure port 12 is connected to a fuel supply line, not shown, and is used to supply a high-pressure chamber 13 with fuel that is under high pressure or under system pressure. The high pressure chamber 13 is formed in a recess 14 of the injector housing 11, in which a valve piece 15 is also inserted. The valve piece 15 has a recess extending from an end face of the valve piece 15 in the form of a blind hole-shaped bore 17 in which a nozzle needle 20 serving as an injection member 19 is arranged so as to be movable along a longitudinal axis 22. The nozzle needle 20 is used in a known manner to open or close at least one injection opening formed in the injector housing 11, via which the fuel can be discharged from the high-pressure chamber 13 into the combustion chamber of the internal combustion engine. In the in the Fig. 1 The position shown for the nozzle needle 20 is in its lowered position that closes the at least one injection opening.

The bore 17, together with one end of the nozzle needle 20 in the valve piece 15, delimits a control chamber 25 which, via a drainage bore 26 extending from the base of the bore 17 and arranged concentrically to the longitudinal axis 22, into a low-pressure region 28 of the injector housing 11 or the Fuel injector 100 can be relieved of pressure. By way of example, the outflow bore 26 has a section having a smaller flow cross section for forming an outflow throttle 29. The control chamber 25 can be filled from the high-pressure chamber 13 by means of at least one inlet bore 30.

The valve piece 15 is seated axially with a section 31 of enlarged diameter on a stepped shoulder 32 of the recess 14 in the injector housing 11 and is axially against the shoulder 32 by means of a clamping nut 34 tense. On the side of section 31 facing away from control chamber 25, valve piece 15 has an approximately pin-shaped extension 35, on whose side facing away from control chamber 25 the drain hole 26 opens.

To control the outflow of fuel from the control chamber 25 into the low-pressure region 28 of the fuel injector 100, it is necessary to tightly close or open the drain hole 26 on the side facing away from the control chamber 25. For this purpose, a conically arranged sealing surface 38 that runs radially around the longitudinal axis 22 is provided on the valve piece 15 near the mouth area 37 of the drain hole 26 ( Figs. 2 and 3 ). The sealing surface 38 acts, as in particular based on the Fig. 3 can be seen, together with a sealing edge 42 which is embodied on a magnet armature 40 serving as a valve member and likewise encompasses radially around the longitudinal axis 22. The magnet armature 40 can be raised and lowered in the direction of the longitudinal axis 22. In the position of the armature 40 shown in the figures, it has its lower position facing the valve piece 15, in which the sealing edge 42 interacts with the sealing surface 38 to form a sealing seat 43 in order to prevent fuel from flowing out of the control chamber 25.

The area of the sealing surface 38 on the valve piece 15 is formed within a recess 45 on the valve piece 15, the recess 45 having a radially circumferential edge 47. In the area of the edge 47, a plurality of outflow bores 48, preferably arranged at equal angular distances from one another, are provided, which are arranged at an inclined angle a, for example between 25 ° and 60 °, with respect to a perpendicular to the longitudinal axis 22. The outflow bores 48 start from the area of the inner wall 49 of the recess 45 and open in the area of a radially circumferential guide area 50 on the extension 35 of the valve piece 15 in the area of an outlet 52 each the mouth area 37 of the drain hole 26, the recess 45 and the drain holes 48 in the low-pressure area 28 of the fuel injector 100.

The magnet armature 40 has an approximately disk-shaped section 54 which runs radially around the longitudinal axis 22 and which is surrounded by a radially circumferential, in Direction to the control chamber 25 projecting guide section 56 is limited. The guide section 56 interacts with its inner wall 58 with the guide region 50 on the extension 35, in such a way that a radial guide for the magnet armature 40 is formed between the extension 35 and the guide section 56. At the level of the outlets 52 of the outflow bores 48, the guide section 56 of the magnet armature 40 preferably has several passage openings 60 arranged in the manner of elongated holes in the circumferential direction of the guide section 56, which are preferably arranged at non-uniform angular distances from one another around the longitudinal axis 22, in order to be independent of the angular position of the magnet armature 40 in relation to the longitudinal axis 22 always to be arranged in overlap with the outlets 52 of the outflow bores 48. Furthermore, the passages 60 have a height such that, regardless of the axial position of the magnet armature 40 in relation to the longitudinal axis 22, an overlap between the outlets 52 and the passages 60 is achieved. The radial guidance of the magnet armature 40 thus takes place both in an axial area above the passages 60 and in an axial area (in each case with reference to the longitudinal axis 22) below the passages 60.

How particularly with the Fig. 2 Furthermore, it can be seen that the plate-shaped section of the magnet armature 40 also has a plurality of further passages 62, preferably arranged at uniform angular intervals around the longitudinal axis 22, in the form of slots protruding radially away from the longitudinal axis 22. These slots extend up to the edge of the disk-shaped section of the magnet armature 40 and beyond that somewhat in the direction of the radially circumferential guide region 50 of the magnet armature 40 Fig. 3 As can be seen, the (lower) end face 64 of the magnet armature 40 facing the valve piece 15 is arranged in the closed position of the magnet armature 40 with the formation of only a small axial gap 65 to the end face 66 in the region of the edge 47 of the valve piece 15.

The armature 40 also has a first extension 68 on the side facing the valve piece 15, which protrudes axially into the recess 45 of the valve piece 15, the sealing edge 42 being formed on the first extension 68. The sealing edge 42 has a distance a from the longitudinal axis 22 which is smaller than the distance A of the inner wall 58 from the Longitudinal axis 22 ( Fig. 3 ). Furthermore, the magnet armature 40 has a second extension 70 on the side facing away from the valve piece 15, the two extensions 68, 70 being penetrated by a through-hole 72, one in the Fig. 1 recognizable anchor bolt 73 surrounded radially. The armature bolt 73 is arranged in the area of a through opening 75 of a magnet core 76. The second extension 70 of the magnet armature 40 dips axially into the through opening 75 of the magnet core 76. On the upper side of the second extension 70 facing away from the first extension 68, a compression spring 78 radially surrounding the armature bolt 73 is supported on the second extension 70, which acts on the magnet armature 40 by spring force and acts on it in the direction of its closed position.

The magnet armature 40 interacts with a magnet coil 80 which is arranged in the area of the magnet core in a recess extending radially around the longitudinal axis 22 and which can be electrically contacted via connection pins 81, 82 or can be supplied with a supply voltage. When the magnet coil 80 is energized, the magnet armature 40 is raised from its closed position counter to the spring force of the compression spring 78 in order to allow pressure media to flow out of the control chamber 25. In this case, the magnet armature 40 rests axially against the magnet core 76 with a residual air gap disk (not shown) in between, whereby the maximum armature stroke of the magnet armature 40 is limited.

When the magnet armature 40 is raised from its closed position and fuel flows out of the control chamber 25 in the direction of the low-pressure region 28 of the fuel injector 100, the nozzle needle 20 plunges more deeply into the control chamber 25, as a result of which the at least one am Fuel injector 100 formed injection opening is released.

In the Fig. 4 is an opposite of the Figs. 2 and 3 modified armature 40a shown. The magnet armature 40a differs from the magnet armature 40 in that it is either made shorter in relation to its axial extent or length, ie has an axially shorter guide section 56, or that the outlets 52 of the outflow bores 48 are below a lower end edge 84 of Guide portion 56 are arranged. As a result, it is not necessary for the magnet armature 40a to have passages 60.

Claims (9)

1. Fuel injector (100), having an injector housing (11), in which an injection element (19) is guided so as to be movable in reciprocating fashion, having a valve piece (15) in which there is formed a recess (17) which, together with the injection element (19), delimits a control chamber (25) which can be relieved of pressure via an outflow bore (26) into a low-pressure region (28) of the injector housing (11), wherein the outflow bore (26) can be opened up and closed by a valve element, which is formed at least indirectly as a magnet armature (40; 40a), by means of a sealing edge (42) in the region of a sealing surface (38) formed on the valve piece (15), and wherein the magnet armature (40; 40a), which interacts with a magnet coil (80), is displaceable along a longitudinal axis (22) and guided radially by a projection (35) of the valve piece on a radially encircling guide region (50) of the valve piece (15), wherein the spacing (a) of the sealing edge (42) on the magnet armature (40; 40a) to the longitudinal axis (22) is smaller than the spacing (A) of a guide section (56; 56a), which interacts with the guide region (50) on the valve piece (15), of the magnet armature (40; 40a) to the longitudinal axis (22),
   characterized in that
   the magnet armature (40; 40a) has a disc-shaped section (54) which radially encircles the longitudinal axis (22) and on the outer circumference of which is arranged the guide section (56; 56a), which projects in the direction of the valve piece (15) and the inner wall (58) of which interacts with the guide region (50) on the valve piece (15).
2. Fuel injector according to Claim 1,
   characterized
   in that the valve piece (15) has at least one, preferably multiple, outflow bores (48) which are arranged at uniform angular intervals about the longitudinal axis (22) and which have an outlet (52) in the region of the guide region (50) of the valve piece (15), wherein the outlet (52) connects the outflow bore (26) for the control chamber (25) to the low-pressure region (28) when the valve element is in a raised state.
3. Fuel injector according to Claim 2,
   characterized
   in that the at least one outflow bore (48) is arranged at an oblique angle (α) with respect to the longitudinal axis (22) such that, in relation to the longitudinal axis (22), the sealing surface (38) has a greater spacing to the control chamber (25) than the outlet (52).
4. Fuel injector according to any one of Claims 1 to 3,
   characterized
   in that the magnet armature (40; 40a) has, in a central region, a pin-like or sleeve-like first projection (68) which projects in the direction of the valve piece (15) and on whose end side facing towards the valve piece (15) the sealing edge (42) is formed, and in that, at least when the magnet armature (40; 40a) is in a lowered state, the first projection (68) protrudes into a depression (45) of the valve piece (15).
5. Fuel injector according to any one of Claims 1 to 4,
   characterized
   in that the magnet armature (40; 40a) has, in a central region, a pin-like or sleeve-like second projection (70) which projects in the direction of the magnet coil (80) and which protrudes axially, with a small degree of radial play, into a passage opening (75) of a magnet core (76).
6. Fuel injector according to any one of Claims 2 to 5,
   characterized
   in that the outlet (52) of the at least one outflow bore (48) opens out, on the side averted from the magnet coil (80), below the magnet armature (40; 40a) .
7. Fuel injector according to any one of Claims 2 to 5,
   characterized
   in that the outlet (52) of the at least one outflow bore (48) opens out in the region of the magnet armature (40), and in that the magnet armature (40) has at least one passage opening (60) which is arranged so as to overlap the outlet (52).
8. Fuel injector according to any one of Claims 1 to 7,
   characterized
   in that the magnet armature (40; 40a) has at least one passage (62) at least in the region of overlap with an end side, facing towards the magnet armature (40; 40a), of the valve piece (15).
9. Use of a fuel injector (100) according to any one of Claims 1 to 8 for auto-ignition internal combustion engines, wherein the fuel injector (100) is designed to operate at a system pressure of more than 2000 bar.

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