BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 shows a schematic representation, in longitudinal section, through a fuel injection valve according to a first embodiment of the invention.
FIG. 2 shows a schematic plan view of a cross-section of a soft-magnet armature arrangement from FIG. 1, cut along the line II-II.
FIG. 3 shows a schematic plan view of a cross-section of a soft-magnet yoke arrangement from FIG. 1, cut along the line III-III.
FIG. 4 shows a schematic plan view of a soft-magnet yoke arrangement having a solenoid arrangement.
FIG. 5 shows a schematic plan view of a soft-magnet yoke arrangement and of a solenoid arrangement, according to a second embodiment of the invention.
FIG. 6 shows a schematic plan view of a soft-magnet yoke arrangement and of a solenoid arrangement, according to a third embodiment of the invention.
FIG. 7 shows a lateral, perspective representation of the soft-magnet yoke arrangement and of the solenoid arrangement according to FIG. 6.
FIG. 8 shows a lateral, partially longitudinal sectional representation of the valve rod, with an armature arrangement which has a box profile.
FIG. 9 shows a perspective side view of a further embodiment of an actuating device according to the invention.
FIG. 10 shows an enlarged, perspective side view of a partial yoke of a yoke disc for an actuating device according to the invention as shown in FIG. 9.
DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS
In FIG. 1, a fuel injection valve, having a valve housing 10 which is substantially rotationally symmetrical in relation to a central longitudinal axis M, is shown in a schematic longitudinal section, in a half-open position. Such a fuel injection valve serves to inject fuel directly into the combustion chamber, not illustrated further, of an internal combustion engine. The fuel injection valve 10 has a radially oriented lateral fuel inlet 12, through which fuel, pressurized by means of a pump or other pressure generator that is not illustrated further, can flow into the fuel injection valve. It is also possible, however, for the fuel inlet to be provided, for instance, in the region of the fuel injection valve that in FIG. 1 is the central, upper region denoted by 14 From the fuel inlet 12, a central fuel channel 16 extends through a tube 17 to a fuel outlet 18. A valve arrangement 20 is provided at the end of the central fuel channel 16, in order to discharge the fuel into the combustion chamber of the internal combustion engine in a controlled manner via the fuel outlet 18.
The valve arrangement 20 is constituted by a valve element 20a, which is provided in the central fuel channel 16 and tapers conically towards the fuel outlet 18, and by a valve seat 20b which cooperates with the valve element 20a and is shaped to correspond to the form of the valve element 20a.
The valve element 20a is connected, through an actuating rod 22, to an actuating device 24 which can be electrically activated, in order to move the valve element 20a between an open position and a closed position (up and down in FIG. 1). Pressurized fuel, coming from the fuel inlet 12 and flowing through the central fuel channel 16, is thereby ejected through the fuel outlet 18 into the combustion chamber in a controlled manner.
The actuating device 24 is constituted by a solenoid arrangement 24a, a magnetically soft magnet yoke arrangement 24b which cooperates therewith, and by a magnetically soft magnet armature arrangement 24c which cooperates therewith. In this case, the magnetically soft magnet yoke arrangement 24b is constituted by two shell halves 24b′ and 24b″ which are joined at approximately the level of the line of cut II-II and have recesses 26a, 26b. In the case of the embodiment according to FIG. 1, in plan view the recesses 26a, 26b have the longitudinal extent shown in FIGS. 4 and 5, and are delimited by pole webs 25a, 25b which likewise have the form of a trapezoid or parallelogram. The recesses 26a, 26b accommodate a respective solenoid arrangement 24a′ and 24a″, which end flush with the respective end faces 27a, 27b of the shell halves 24b′ and 24b″.
The end faces 27a, 27b of the shell halves 24b′ and 24b″ delimit a cavity 28 in which the magnet armature arrangement 24c is accommodated so as to be movable along the central axis M.
In the arrangement shown in FIG. 1, the solenoid arrangements and the magnet yoke arrangement have the configuration shown in FIG. 4, in which the pole webs 25a, 25b are of substantially rectangular shape and are disposed next to one another, so as to form intermediate spaces for accommodating the solenoid arrangements 24a′, 24a″. In this case, the pole webs 25a, 25b are preferably disposed in parallel to one to another. The magnet yoke arrangement in this case may be made from single-piece soft iron, from which the pole webs, and the intermediate spaces, are formed. Openings in the form of slots or oblong holes, which are filled with electrically insulating material, can be worked into such a single-piece soft-iron preform. It is also possible, however, for the magnet yoke arrangement to be produced as a preform from sintered iron powder, or to be assembled from a plurality of sub-sections, that are insulated from one another if necessary, and, for example, to be bonded together.
FIG. 2 shows the magnetically soft magnet armature arrangement 24c. It has a magnetically soft armature disc 24c, which is disposed around the central axis M. In order to keep the eddy currents induced in the armature disc 24c as small as possible during operation of the fuel injection valve, the armature disc 24c is provided with radially oriented openings 36. These openings have the form of slots 36 extending to the edge 30 of the armature disc 24c. There are thereby created radially oriented strips 25, which are connected to one another in the centre of the disc 24c.
FIG. 3 shows the magnetically soft magnet yoke arrangement 24b in cross-section. In order to keep the eddy currents induced in the magnet yoke arrangement 24b as small as possible during operation of the fuel injection valve, the magnet yoke arrangement 24b is provided with a multiplicity of radially oriented vertical openings 36 in the form of slots. In order to render the fuel injection valve of a fluid-tight design, a material web 38 is provided at the outer wall, between the slots 36, said material web effecting a closed circumferential surface. Alternatively, the closed circumferential surface may also be disposed at the radially inner ends of the slots 36. This also has the advantage of possibly improving dissipation of heat out of the magnet yoke. In this case, both shell halves 24b′ and 24b″ of the magnet yoke arrangement 24b are provided with the slots 36.
It becomes evident from the above that the solenoid arrangement 24a and the radially oriented strips 25 of the magnetically soft armature disc 24c may be oriented substantially orthogonally in relation to one another. It is understood that this may be realized either in the form described above, with radially oriented strips 25 of the armature arrangement 24b and a spiral-shaped solenoid arrangement 24a or magnet yoke arrangement 24b, or vice versa. It is also possible, however, for the actuating device 24 to be realized with concentric armature parts and a solenoid arrangement shaped in the form of a star.
The magnet armature arrangement 24c is a circular iron-containing disc of a shape described in detail below. The solenoid arrangement 24a and the magnet armature arrangement 24c overlap in the radial direction in relation to the central axis (M). As shown in FIG. 1, the solenoid arrangement 24a has a smaller outer diameter than the armature disc 24c, such that the magnetic flux originating from the solenoid arrangement 24a enters the armature disc 24c virtually without appreciable stray losses. There is thus realized a particularly efficient magnetic circuit, which allows very short valve opening/closing times and high holding forces.
Irrespective of the design of the magnet yoke and solenoid arrangement, the armature disc 24c may also be a closed circular disc of soft iron, provided that design of the magnet yoke and solenoid arrangement described above ensures that the stray losses or eddy current losses are small enough for the respective application.
As illustrated in FIG. 1, the armature disc 24c is rigidly connected to the actuating rod 22, and accommodated, so as to be moveable longitudinally along the central axis M and guided in the tube 17, in an armature space 34 which is delimited by the shell halves 24b′ and 24b″ of the magnet yoke arrangement 24b. In this case, the armature disc 24c with the actuating rod 22 is subjected to load by a helical spring 40 disposed coaxially in relation to the central axis M, such that the valve element 20a present at the end of the actuating rod 22 sits in a fluid-tight manner in the valve seat 20b, i.e. is forced into its closed position. When one of the coils (for example 24a′) of the solenoid arrangement 24a is energized, there is induced in the magnet yoke arrangement 24b a magnetic field which has a low eddy-current content and draws the armature disc 24c with the actuating rod 22 in the direction of the respective shell-half 24b′ in which the energized coil is located. The valve element 20a thus moves away from the valve seat 20b, into its open position. When the other coil (for example 24a″) of the solenoid arrangement 24a is energized, the valve element 20a moves into the respectively other position, towards the valve seat 20b, into its closed position. A helical spring 40, which is at the end of the actuating lever 22 distant from the valve element 20a and which acts upon said actuating lever, holds the valve element 20a in its closed position when the solenoid arrangement 24a is not energized.
A development of the invention consists in coupling a plurality of armature discs 24c (two or more) to the valve element 20a via the actuating rod 22, a coil yoke arrangement acting upon said armature discs from one or both sides in each case. In addition, the coil arrangement 24a may in each case be realized in multiple parts on both sides of the magnetically soft magnet armature arrangement 24c. In this case, there are respectively provided two or more solenoid arrangements 24a′, 24a″, which end substantially flush with the respective end faces 27a, 27b of the shell halves 24b′ and 24b″. This embodiment can have an increased magnetic field density for an equal structural volume, and thus also have an increased valve-element holding force and valve-element actuating speed. In this case, current directed in opposite directions flows alternately through the individual coils on one side (above or below) of the respective magnet armature arrangement 24c. In this case, the yoke iron between the individual coils 24a of one side may be constituted by iron plates which are insulated from each other.
The two embodiments are shown with actuating devices 24 which can be electrically activated, in which a central actuating rod 22 is moved by a disc-shaped magnet armature arrangement 24c. Instead of the central actuating rod 22, it is also possible to provide a tube, the magnet armature being disposed on its end face. In the case of the embodiment of the magnet yoke and the solenoids according to FIG. 4, each individual pole web is surrounded by a separate winding. To provide a better overview, not all pole webs are shown provided with solenoid arrangements in FIG. 4. In this case, all solenoid arrangements 24a′ and 24a″ are either wound in opposite directions and energized in the same direction, or are wound in the same direction and energized in opposite directions, in order for respectively oppositely directed electric current to be taken past opposing flanks 25a′, 25a″ of the pole webs 25a, 25b.
Alternatively, it is also possible for the solenoid arrangement to be realized in the configuration shown in FIG. 5, in which one (or more) winding(s) is (are) inserted in the form of a meander into the recesses 26a, 26b between the pole webs 25a, 25b of the magnet yoke arrangement. Here, likewise, respectively oppositely directed electric current is taken past opposing flanks 25a′, 25a″ of each of the pole webs 25a, 25b. In the case of all embodiments, it is evident that the pole webs 25a, 25b (and also the recesses 26a 26) are of a shape which is substantially asymmetrical in relation to the central longitudinal axis M of the fuel injection valve, at least one solenoid arrangement 24a′, 24a″ at least partly enclosing pole webs of non-circular shape in such a way that oppositely directed electric current is taken past the flanks of said pole webs.
The embodiment of a solenoid arrangement 24a shown in FIGS. 6 and 7 is produced in an integrated manner with the magnetically soft magnet yoke arrangement 24b which cooperates therewith. For this purpose, an elongated yoke plate 50 containing soft iron is surrounded on both sides by a conductor strip 52, in that the latter is bent around a longitudinal edge 50′—which in the subsequent, finished state is on the inside—of the yoke plate 50. Disposed next to the conductor strip 52 is a plate band 54 which contains soft iron, is just as thick as the conductor strip 52 and is likewise bent around the longitudinal edge 50′—which in the finished state is on the inside—of the yoke plate 50. The plate band 54 next to the conductor strip 52, together with the portion of the yoke plate 50 on which it bears flatly, serves—in the finished state —to constitute the back of the magnet yoke. The conductor strip 52 projects beyond the lateral longitudinal edge 50″—which in the finished state is on the outside—of the yoke plate 50 at both ends, for the purpose of electrical contacting. A second layer of an elongated yoke plate 56 containing a soft iron is then is then laid against said conductor strip, so as to produce a layer structure consisting of the first yoke plate 50, the conductor strip 52 and the plate band 54, and the second yoke plate 56. This layer structure is then rolled together in the form of a spiral, in the manner shown in FIG. 6, in order to obtain the overall structure consisting of a coil and a yoke. After having been rolled together in the form of a spiral, the first and second yoke plates 50, 56 lie close to one another, and the overall structure is a cylindrical winding body. It is understood that the conductor strip 52 is electrically insulated against the soft-iron parts 50, 54, 56.
The air gap, shown in FIG. 1, between the magnet yoke arrangement 24b and the magnet armature arrangement 24c, said air gap being coaxial in relation to the central longitudinal axis M and being formed when the actuating device 24 is in its neutral position, is approximately 10 times larger than the grid dimension of the pole webs. In the case of this embodiment, the grid dimension is the transverse dimension of the pole webs. In the case of the embodiment of the magnet yoke arrangement 24b according to FIGS. 6, 7, the grid dimension is the thickness of the yoke plate 40. Other geometries of the pole webs are also possible. Determinant for the grid dimension are the smallest structures of the pole webs, i.e. their longitudinal dimensions, transverse dimensions, thickness, etc., that result in a small-sized shape of the poles of the magnet yoke which act upon the magnet armature. This small grid dimension results in a high magnetic flux density, and consequently in high attractive or holding forces of the valve arrangement and also in a low switching time, since the electric and magnetic losses, or the induced counterforces, are very small.
FIG. 8 shows a further alternative for a development of the armature arrangement. In this case, the armature disc 24c is of a multilayer structure. In order to increase the mechanical solidity, a ceramic layer 24c″ is disposed between two soft-iron layers 24c′ which are relatively thin—and therefore have a low eddy-current content—and attached to the valve rod 22. It is understood that the two soft-iron layers 24c′ may be either complete armature discs or discs which have been recessed in the manner described above. A plurality of such armature arrangements may also be distributed along the valve rod 22.
FIG. 9 shows a partial view of a further development of the magnet yoke arrangement 24b according to the invention, in which respectively two partial yokes 125a of substantially semicircular disc shape are joined together to form a yoke disc 125 of the magnet yoke arrangement 24b. In the centre of each yoke disc 125 composed of two partial yokes 125a of semicircular disc shape is a semi-cylindrical recess 125′ (see FIG. 10), which accommodates a bearing bushing 126 for the valve rod 22. Each yoke disc is thus composed of at least two partial yokes which contain soft iron and surround an actuating rod which supports the magnet armature arrangement. The respective partial yokes of a yoke disc are bonded to each other.
The two faces 128, 130 of each yoke disc 125 of the magnet yoke arrangement—apart from the yoke discs at the two ends of the yoke-disc stack in FIG. 9—have a respective pole web 25a, 25b, which together with the solenoid arrangement 24a′, 24a″ acts upon the magnet armature arrangement 24c. In this case the magnet armature arrangement 24c is constituted by a corresponding number of soft-iron discs which are welded onto the valve actuating rod 22 and are provided with a multiplicity of bores through which the fuel can flow when the magnet armature arrangement 24c moves between its end positions.
In the region of its outer circumferential surface, each partial yoke 125a has an integrally formed spacer 130 which concomitantly determines the dimension X of the cavity 28 between the two yoke discs 125, In addition, electrical connecting pieces 132 for the solenoid arrangement 24a′, 24a″ are disposed in the region of the outer circumferential surface of the yoke disc 125. Solenoid arrangements 24a′, 24a″ facing respectively the same side of the magnet armature arrangements 24c are thus connected for co-phasal electrical activation in series or parallel connection.
The magnet armature arrangements 24c disposed on the actuating rod 22 thus constitute a sub-assembly, which is to be assembled with the two further sub-assemblies constituted by stacked partial yokes that are held apart.
A pressure-proof housing surrounds the actuating device 24 and the valve arrangement 20, electrical connections being routed outwards from said housing, by means is of glass bushings, from the electrical connecting pieces 132 for the solenoid arrangements 24a′, 24a″.
The solenoid arrangements 24a′, 24a″ are realized as copper-containing preforms which are electrically insulated by means of aluminium oxide coating or the like. These preforms are mounted around the pole webs 25a, 25b and, following joining together of the sub-assembly constituted by individual stacked partial yokes that are held apart, are connected to the electrical connections Finally, the solenoid arrangements 24a′, 24a″ are embedded in the recesses of the partial yokes.
Patent Application
20080092854
