Title of Invention	"A SOLENOID UNIT FOR A SOLENOID VALUE AND THE METHOD OF MANUFACTURING THE SOLENOID UNIT"
Abstract	The invention relates to a solenoid unit for a solenoid valve, including a magnet coil (10) and a ferromagnetic circuit which surrounds the magnet coil (10) and comprises a stationary magnet housing, a movable magnet armature (14) and, if required, an armature antipole (16), the magnet housing being assembled of a cover (18), a shell (22) and a bottom (20) in the form of multilayer transformer sheet metal parts. The invention further relates to a method of manufacturing such a solenoid unit and to a method of manufacturing a magnet housing for such a solenoid unit.

Title of Invention

"A SOLENOID UNIT FOR A SOLENOID VALUE AND THE METHOD OF MANUFACTURING THE SOLENOID UNIT"

Abstract

The invention relates to a solenoid unit for a solenoid valve, including a magnet coil (10) and a ferromagnetic circuit which surrounds the magnet coil (10) and comprises a stationary magnet housing, a movable magnet armature (14) and, if required, an armature antipole (16), the magnet housing being assembled of a cover (18), a shell (22) and a bottom (20) in the form of multilayer transformer sheet metal parts. The invention further relates to a method of manufacturing such a solenoid unit and to a method of manufacturing a magnet housing for such a solenoid unit.

Full Text	B 4561 WO Solenoid Unit and Methods of Manufacturing such Solenoid Unit and of Manufacturing a Magnet Housing for such Solenoid Unit The present invention relates to a solenoid unit for a solenoid valve, comprising a magnet coil and a ferromagnetic circuit which surrounds the magnet coil and includes a stationary magnet housing and a movable magnet armature. The invention further relates to a method of manufacturing such a solenoid unit and to a method of manufacturing a magnet housing for such a solenoid unit. Electromagnetically driven valves have a magnet coil, a magnet armature for opening and closing the valve, and a magnet housing. In the case of simple designs, the magnet housing is made up of a solid sheet metal part bent into a U- shape. These designs are preferably suitable for a direct current control. In the case of an alternating current control, these designs produce heavy eddy current losses. Bearing in mind the permissible heating, a lower amount of effective power and, hence, less magnetic force is thus available. In addition, it is known from the generic document DE 198 60 631 A1, for example, to produce the magnet housing in one piece from a sheet metal strip which is first punched out and subsequently rolled or bent. There are, however, only limited possibilities of shaping here. Other alternating current operated solenoid valves are provided with magnet housings made of sintered ferrite material to avoid eddy currents. While these housings are also suitable for direct voltage operation, two valve configurations are fabricated for reasons of cost-saving. In contrast to an alternating current operated valve, no expensive special material such as sintered ferrite is used for the magnet housing of a direct current operated valve, but reasonably priced sheet steel. The invention provides a solenoid unit for a solenoid valve, in which the magnet housing is assembled of a cover, a shell and a bottom in the form of multilayer transformer sheet metal parts. One advantage resides in the favorable shape of the magnet housing, because it encloses the magnet coil. Furthermore, thin sheet metal layers can be shaped for a precise fit without great effort, and -2- the electrical resistance at the layer boundaries is already sufficient to reduce eddy current effects to an acceptable degree. Accordingly, it is no longer necessary to manufacture two valve types, for direct current and for alternating current, for cost reasons. Transformer sheets are especially suitable because, in addition to the appropriate magnetic properties, they have a low thickness of a few tenths of a millimeter. Moreover, transformer sheets are mass-produced on an industrial scale and, hence, are available for use at low cost. In addition, they are also available with an electrically insulating coating, which is of advantage for an even greater reduction of the eddy currents. In one embodiment, the transformer sheet metal parts are punched and, if required, bent. Since the sheet metal parts used are of a low thickness, these machining steps can be carried out simply and at low cost. The transformer sheet metal parts have a plurality of layers, it being possible that these layers are connected to each other. This increases the stability of the transformer sheet metal parts and reduces the gap width between the individual layers. Suitable connecting methods include packing of laminations, gluing or riveting, for example. The bottom and/or the cover may have a central opening. This allows a simple assembly of the solenoid unit, by simply axially inserting the armature, the armature antipole and/or a core guide tube. In this embodiment, a radial slot is preferably provided in the cover and/or in the bottom, the slot being continuous from the central opening up to the outer periphery. This slot reduces an occurrence of eddy currents in the peripheral direction of the cover and the bottom. In the assembled condition, the bottom and/or the cover may be caulked to the shell. This is a particularly reasonably priced and reliable type of attachment. Prior to connecting the sheet metal parts, the magnet coil may be introduced into the shell without problems, so that by the caulking process a preassembled unit consisting of the bottom, the cover, the shell and the magnet coil is provided in a very simple manner. -3- ln a further embodiment, the shell of the magnet housing has at least one aperture, and the magnet coil is potted or is coated or encased by injection- molding. A liquid plastic mass is introduced through this aperture into the magnet housing, so that the magnet coil is embedded in plastic material. After the curing of the plastic mass, any gaps or cavities are closed off, and the sheet metal parts of the magnet housing and also the magnet coil are fixed in place such that any rattling noises in the operation of the valve can no longer occur. The shell may have a thickness that is lower than that of the bottom, and the bottom may have a thickness that is greater than that of the cover. This compensates for increased magnetic reluctances, which appear primarily at the bottom due to the non-magnetic core guide tube and the air gap to the movable magnet armature, by greater sheet metal part thicknesses. Owing to the multilayer structure of the sheet metal parts, the sheet metal part thickness can be varied very easily by varying the number of layers. The stacked sheet metal parts of the cover, the shell and the bottom may differ with respect to the thickness and the characteristics of the individual metal sheets, e.g. they may or may not be insulated. In one embodiment, the cover comprises an inner cover part and an outer cover part, the outer contour of the inner cover part being complementary to the inner contour of the outer cover part, so that the cover parts can be assembled with an interlocking fit. In this context, it is not a single transformer sheet of the cover that is referred to as a cover part, but a sheet stack built up of a plurality of transformer sheets. This structure made up of two cover parts offers the advantage that the inner cover part, which is comparatively more complicated to produce, can be identically constructed and made use of even with covers of different sizes, and the required adaptation is effected by the outer cover part, which is less complicated to produce. Because of the interlocking connection, the cover, which is composed of the inner and outer cover parts, essentially gives the impression of being a one-piece cover (although built up of a plurality of sheet metal layers), so that the magnetic flux in the plane of the cover is not impaired. Preferably, the outer cover part is formed in the shape of a U. In this way, the protective ground conductor connection of the inner cover part, which is -4- substantially responsible for the increased manufacturing expense of the inner cover part, is well accessible, whatever the size of the cover. Furthermore, the cover may have a covering part which covers the cover parts in the assembled condition. In the case of larger covers, by means of this covering part, firstly the sheet metal part thickness of the stack of sheets is increased and secondly the base area of the cover is not separated across its entire thickness by a joint between the inner and outer cover parts. Both factors contribute to a reduction in the magnetic reluctance. The invention further comprises a method of manufacturing a magnet housing of a solenoid unit for a solenoid valve, comprising the following steps: A) punching of metal sheets of a ferromagnetic material; B) stacking the metal sheets to form sheet stacks which are used for the shell, the bottom or the cover or a cover part of a magnet housing of the solenoid unit; C) assembling the magnet housing by producing an interlocking connection between the cover and the shell and between the bottom and the shell. This method results in a simple and reasonably priced manufacture of a magnet housing for a solenoid unit which is suitable both for direct current control and alternating current control. In some embodiments, the cover is assembled from an inner cover part and an outer cover part before assembling the magnet housing, the outer contour of the inner cover part being complementary to the inner contour of the outer cover part. Preferably, the cover parts are then connected with an interlocking fit and/or with a frictional fit. The interlocking connection, but also a possible frictional engagement perpendicular to the plane of the cover provide for an unimpeded magnetic flux in the cover plane and are simple to produce. The cover parts having the complementary contours are preferably punched; the frictional connection may be obtained by means of a press fit between the cover parts, for example. When the U-shaped cover part is connected to the inner cover part with an interlocking fit, its legs may be slightly pressed apart and deformed, so that, when the connecting process is completed, the legs clamp the inner cover part in -5- place and prevent a relative movement between the cover parts perpendicularly to the cover plane. Subsequent to assembling the inner and outer cover parts, a covering part may additionally be mounted to the inner and/or to the outer cover part. As the surface area of the cover increases, the thickness of the cover may also be adjusted, i.e. enlarged, very easily by means of such a covering part which, just like the inner and outer cover parts, is composed of transformer sheets. The covering part is caulked to the inner and/or to the outer cover part, for example. In addition, the invention comprises a method of manufacturing a solenoid unit for a solenoid valve, which includes the following steps: A) punching of metal sheets of a ferromagnetic material; B) stacking the metal sheets to form sheet stacks which are used for the shell, the bottom or the cover or a cover part of a magnet housing of the solenoid unit; C) shaping the shell such that it can at least partially surround a magnet coil; D) inserting the magnet coil into the shell; E) assembling the magnet housing by producing an interlocking connection between the cover and the shell and between the bottom and the shell. In one variant of the method, the assembling of the magnet housing starts already prior to inserting the magnet coil into the shell by already producing an interlocking connection between the bottom and the shell or between the cover and the shell. Accordingly, this partial step is omitted in step E. By means of this method, the magnet housing and the magnet coil are produced as a preassembled unit right away, with the magnet coil being located protected in the interior of the preassembled unit. After fitting a fixed armature antipole and a core guide tube having a movable magnet armature, the solenoid unit is complete. Subsequent to assembling the magnet housing, a liquid plastic mass is preferably introduced into the assembled magnet housing through an aperture -6- provided in the magnet housing, for embedding the magnet coil. The aperture is produced e.g. by punching before or after the stacking of the metal sheets. After the plastic mass has been introduced and has cured, the sheet metal parts of the magnet housing and the magnet coil are fixed in place, so that no rattling noises can occur. Further features and advantages of the invention will be apparent from the description below of a preferred embodiment with reference to the drawings, in which: - Figure 1 shows a diagrammatic section through a solenoid unit; - Figure 2 shows a perspective view of a cover, a bottom and a shell of a solenoid unit according to the invention; - Figure 3 shows a perspective view of an inner cover part and an outer cover part; - Figure 4 shows a perspective view of a cover for a solenoid unit according to the invention, the cover being assembled of the inner and outer cover parts according to Figure 3; and - Figure 5 shows a perspective exploded view of a magnet housing for a solenoid unit according to the invention, including a multipart cover. Figure 1 shows a solenoid unit for actuating a solenoid valve, including a magnet coil 10 determining a coil axis A and having a winding that is received by a bobbin 12. Further illustrated is a ferromagnetic circuit which in Figure 1 comprises a stationary magnet housing, a movable magnet armature 14 and a stationary armature antipole 16. In the present case, the magnet housing has a cover 18, a bottom 20 and a shell 22. In addition, a non-magnetic core guide tube 24 is provided which extends inside the magnet coil 10 between the bobbin 12 and the magnet armature 14 and armature antipole 16. The power supply to the magnet coil 10 is effected via connections 26 led through axially, which are likewise illustrated diagrammatically. When the magnet coil 10 is in the de-energized condition, the magnet armature 14 generally is biased by a spring (not shown) such that the solenoid valve is in a desired position (opened or closed). When a current is fed to the -7- magnet coil 10, an axially oriented magnetic field develops inside the magnet coil. The magnet armature 14, the armature antipole 16 and the magnet housing (to be more precise, the cover 18, the bottom 20 and the shell 22) form a ferromagnetic circuit which is decisive for the force exerted on the magnet armature 14. An axial air gap 28 exists between the magnet armature 14 and the armature antipole 16, so that the magnet armature 14 is attracted towards the armature antipole 16. The axial extent of the air gap 28 is equivalent to a driving lift of the solenoid valve. Figure 2 shows an especially advantageous embodiment of the magnet housing, consisting of the cover 18, the bottom 20 and the shell 22. It can be seen that the sheet metal parts of the magnet housing are built up of multiple layers of transformer sheet metal, the cover 18 and the bottom 20 having a plurality of layers in the axial direction and the shell 22 in the radial direction. The orientation of the sheet stacks, that is, the axial lamination for the cover 18 and the bottom 20 and the radial lamination of the shell 22, is selected to correspond to the course of the magnetic flux lines, with the eddy current paths which run perpendicularly to the magnetic flux lines being however interrupted at the layer boundaries. In the present embodiment, the individual layers consist of transformer sheet metal which has a thickness of about 1 mm and may be coated with an electrically insulating coating. As a rule, however, a mere lamination of non- insulated transformer sheets is sufficient to largely eliminate the eddy currents as a result of the increased electrical resistance at the layer boundaries. Figure 2 shows, by way of example, some layers for the respective housing components, which are however only symbolic of a multilayer structure. With layer thicknesses of 1 to 1.2 mm, the individual components preferably comprise 2 to 9 layers. For the purpose of increasing the stability and reducing the gaps, the layers of the components may be connected with each other, e.g. by packing of laminations, gluing or riveting. The thickness of the sheet metal parts of the magnet housing may be appropriately selected very easily by varying the number of layers. As a rule, the bottom 20, for example, includes more layers than the cover 18 or the shell 22, in order to at least partly compensate for the increased magnetic reluctance in the -8- region of the bottom 20 caused by the non-magnetic core guide tube 24 and the air gap between the core guide tube 24 and the movable magnet armature 14. Tabs 32 on the shell 22 may be inserted into recesses 30 provided in the cover 18 and the bottom 20. The cover 18 and the bottom 20 are each connected with the shell 22 by assembling the parts and by caulking the tabs 32. The magnet coil 10 may be inserted axially without problems prior to the assembly of the magnet housing and is enclosed inside the magnet housing after caulking of the tabs 32. According to another embodiment, the cover 18 and/or the bottom 20 are welded or screwed to the shell 22, Figure 2 shows that the shell 22 is provided with a plurality of apertures 36 through which a liquid plastic mass is introduced after insertion of the magnet coil 10 and assembly of the magnet housing, in order to embed the magnet coil 10 and fix it in place. Commonly used methods of embedding the magnet coil 10 include encasing or coating by injection-molding, or potting. The apertures 36 are preferably provided at places where the effect of the ferromagnetic circuit is least impaired. The cover 18 or the bottom 20 may, of course, also have apertures for this purpose. The cover 18 and the bottom 20 each have a central opening for insertion of the core guide tube 24 with the magnet armature 14 or of the armature antipole 16. Furthermore, the cover 18 and the bottom 20 each have a radial slot 34 which is continuous from the central opening as far as to the outer periphery, the slot reducing formation of eddy currents in the peripheral direction of the cover 18 and the bottom 20. Depending on the respective production series of the solenoid valve, the individual sheet metal parts of the magnet housing may exhibit special features. For example, in Figure 2 the substantially circular cover 18 is cut off along a chord so as to make it easier for the connections 26 of the magnet coil 10 to be led through axially. The extent of the shell 22 in the peripheral direction is essentially dependent on the production series of the valve and merely needs to ensure sufficient magnetic flux. Preferably, however, the multilayer shell 22 surrounds at least half of the magnet coil 10 and, in an extreme case, encloses it entirely, but in the latter case at least one axially extending slot should be provided to reduce an occurrence of eddy currents in the peripheral direction. -9- Figures 3 and 4 show an inner cover part 38 and an outer, U-shaped cover part 40 and, respectively, a cover 18 assembled of these cover parts 38, 40. For the sake of simplicity, only a cover 18 or cover parts 38, 40 are mentioned below, but, of course, the bottom 20 may also be a multi-piece part, assembled of appropriate bottom parts. The method of manufacturing the multi-piece cover 18 will now be explained with reference to Figures 3 and 4. First, the inner and outer cover parts 38,40 are produced in a similar manner to the bottom 20 and the shell 22 by punching, stacking and combining ferromagnetic transformer sheets, the outer contour of the inner cover part 38 being complementary to the inner contour of the outer cover part 40. To form a protective ground conductor connection 42 on one side of the inner cover part 38, some of the transformer sheets are provided with recesses and others with projections across the height of the cover 18, resulting in a complex contour the manufacturing of which involves increased tool costs. Because of this higher manufacturing expense, all the embodiments use an identically constructed inner cover part 38 with the protective ground conductor connection 42. In the case of small magnet housings, the inner cover part 38 constitutes the whole cover 18, whereas in the case of larger magnet housings, the U-shaped outer cover part 40, which is simple to produce, is connected with the inner cover part 38 with an interlocking and/or a frictional fit. In that case, the recesses 30 of the inner cover part 38 serve for the interlocking connection with corresponding projections 44 of the outer cover part 40, rather than for a connection with the shell 22 (cf. Figure 2). For an improved interlocking and/or frictional connection between the cover parts 38, 40, additional cooperating grooves and projections may be provided, which are illustrated in dashed lines in Figure 4. Figure 5 shows an exploded view of a magnet housing having a cover 18 made up of multiple pieces. In order to be able to also adjust the sheet metal part thickness of the cover 18 in the case of larger covers 18, a covering part 46 is provided; this covering part 46 covers the cover parts 38, 40, i.e. the base area of the covering part 46 is the same as the base area of the inner and outer cover parts 38, 40 when in the assembled condition. In this case the shell 22, the outer cover part 40 and the covering part 46 are caulked to each other using the tabs 32 of the shell 22 which, in comparison with those in Figure 2, are somewhat -10- longer. In addition, the covering part 46 may also be firmly connected with the inner cover part 38. To reduce eddy currents in the peripheral direction of the cover 18, the covering part 46 is likewise provided with a radial slot 34. -11 - Claims 1. A solenoid unit for a solenoid valve, comprising a magnet coil (10) and a ferromagnetic circuit which surrounds the magnet coil (10) and includes a stationary magnet housing and a movable magnet armature (14), characterized in that the magnet housing is assembled of a cover (18), a shell (22) and a bottom (20) in the form of multilayer transformer sheet metal parts. 2. The solenoid unit according to claim 1, characterized in that the transformer sheet metal parts are punched and, if required, bent. 3. The solenoid unit according to either of the preceding claims, characterized in that the transformer sheet metal parts have a plurality of layers, these layers being connected to each other. 4. The solenoid unit according to any of the preceding claims, characterized in that the cover (18) and/or the bottom (20) have/has a central opening. 5. The solenoid unit according to claim 4, characterized in that the cover (18) and/or the bottom (20) have/has a radial slot (34) that is continuous from the central opening up to the outer periphery. 6. The solenoid unit according to any of the preceding claims, characterized in that in the assembled condition, the cover (18) and/or the bottom (20) are/is caulked to the shell (22). 7. The solenoid unit according to any of the preceding claims, characterized in that the shell (22) has at least one aperture (36) and the magnet coil is potted or is coated or encased by injection-molding. 8. The solenoid unit according to any of the preceding claims, characterized in that the shell (22) has a thickness that is lower than that of the bottom (20). 9. The solenoid unit according to claim 8, characterized in that the bottom (20) has a thickness that is greater than that of the cover (18). 10. The solenoid unit according to any of the preceding claims, characterized in that the cover (18) comprises an inner cover part (38) and an outer cover part (40), the outer contour of the inner cover part (38) being complementary to the -12- inner contour of the outer cover part (40), so that the cover parts (38, 40) can be assembled with an interlocking fit. 11. The solenoid unit according to claim 10, characterized in that the outer cover part (40) is formed in the shape of a U. 12. The solenoid unit according to claim 10 or 11, characterized in that the cover (18) has a covering part (46) which covers the cover parts (38, 40) in the assembled condition. 13. A method of manufacturing a magnet housing of a solenoid unit for a solenoid valve, comprising the following steps: punching of metal sheets of a ferromagnetic material; stacking the metal sheets to form sheet stacks which are used for the shell (22), the bottom (20) or the cover (18) or a cover part of a magnet housing of the solenoid unit; assembling the magnet housing by producing an interlocking connection between the cover (18) and the shell (22) and between the bottom (20) and the shell (22). 14. The method according to claim 13, characterized in that prior to step C), the cover (18) is assembled from an inner cover part (38) and an outer cover part (40), the outer contour of the inner cover part (38) being complementary to the inner contour of the outer cover part (40). 15. The method according to claim 14, characterized in that the cover parts (38, 40) are connected with an interlocking fit and/or with a frictional fit. 16. The method according to claim 14 or 15, characterized in that subsequent to assembling the inner and outer cover parts (38, 40), a covering part (46) is mounted to the inner and/or to the outer cover part (38, 40). 17. A method of manufacturing a solenoid unit for a solenoid valve, comprising the following steps: A) punching of metal sheets of a ferromagnetic material; -13- B) stacking the metal sheets to form sheet stacks which are used for the shell (22), the bottom (20) or the cover (18) or a cover part of a magnet housing of the solenoid unit; C) shaping the shell (22) such that it can at least partially surround a magnet coil (10); D) inserting the magnet coil (10) into the shell (22); E) assembling the magnet housing by producing an interlocking connection between the cover (18) and the shell (22) and between the bottom (20) and the shell (22). 18. The method according to claim 17, characterized in that the assembling of the magnet housing starts already prior to inserting the magnet coil (10) into the shell (22) by producing an interlocking connection between the bottom (20) and the shell (22) or between the cover (18) and the shell (22). 19. The method according to claim 17 or 18, characterized in that subsequent to step E), a liquid plastic mass is introduced into the assembled magnet housing through an aperture (36) provided in the magnet housing, for embedding the magnet coil (10). The invention relates to a solenoid unit for a solenoid valve, including a magnet coil (10) and a ferromagnetic circuit which surrounds the magnet coil (10) and comprises a stationary magnet housing, a movable magnet armature (14) and, if required, an armature antipole (16), the magnet housing being assembled of a cover (18), a shell (22) and a bottom (20) in the form of multilayer transformer sheet metal parts. The invention further relates to a method of manufacturing such a solenoid unit and to a method of manufacturing a magnet housing for such a solenoid unit.

Full Text

B 4561 WO
Solenoid Unit and Methods of Manufacturing such
Solenoid Unit and of Manufacturing a Magnet Housing
for such Solenoid Unit
The present invention relates to a solenoid unit for a solenoid valve,
comprising a magnet coil and a ferromagnetic circuit which surrounds the magnet
coil and includes a stationary magnet housing and a movable magnet armature.
The invention further relates to a method of manufacturing such a solenoid unit
and to a method of manufacturing a magnet housing for such a solenoid unit.
Electromagnetically driven valves have a magnet coil, a magnet armature for
opening and closing the valve, and a magnet housing. In the case of simple
designs, the magnet housing is made up of a solid sheet metal part bent into a U-
shape. These designs are preferably suitable for a direct current control. In the
case of an alternating current control, these designs produce heavy eddy current
losses. Bearing in mind the permissible heating, a lower amount of effective
power and, hence, less magnetic force is thus available. In addition, it is known
from the generic document DE 198 60 631 A1, for example, to produce the
magnet housing in one piece from a sheet metal strip which is first punched out
and subsequently rolled or bent. There are, however, only limited possibilities of
shaping here.
Other alternating current operated solenoid valves are provided with magnet
housings made of sintered ferrite material to avoid eddy currents. While these
housings are also suitable for direct voltage operation, two valve configurations
are fabricated for reasons of cost-saving. In contrast to an alternating current
operated valve, no expensive special material such as sintered ferrite is used for
the magnet housing of a direct current operated valve, but reasonably priced
sheet steel.
The invention provides a solenoid unit for a solenoid valve, in which the
magnet housing is assembled of a cover, a shell and a bottom in the form of
multilayer transformer sheet metal parts. One advantage resides in the favorable
shape of the magnet housing, because it encloses the magnet coil. Furthermore,
thin sheet metal layers can be shaped for a precise fit without great effort, and

-2-
the electrical resistance at the layer boundaries is already sufficient to reduce
eddy current effects to an acceptable degree. Accordingly, it is no longer
necessary to manufacture two valve types, for direct current and for alternating
current, for cost reasons.
Transformer sheets are especially suitable because, in addition to the
appropriate magnetic properties, they have a low thickness of a few tenths of a
millimeter. Moreover, transformer sheets are mass-produced on an industrial
scale and, hence, are available for use at low cost. In addition, they are also
available with an electrically insulating coating, which is of advantage for an even
greater reduction of the eddy currents.
In one embodiment, the transformer sheet metal parts are punched and, if
required, bent. Since the sheet metal parts used are of a low thickness, these
machining steps can be carried out simply and at low cost.
The transformer sheet metal parts have a plurality of layers, it being possible
that these layers are connected to each other. This increases the stability of the
transformer sheet metal parts and reduces the gap width between the individual
layers. Suitable connecting methods include packing of laminations, gluing or
riveting, for example.
The bottom and/or the cover may have a central opening. This allows a
simple assembly of the solenoid unit, by simply axially inserting the armature, the
armature antipole and/or a core guide tube.
In this embodiment, a radial slot is preferably provided in the cover and/or in
the bottom, the slot being continuous from the central opening up to the outer
periphery. This slot reduces an occurrence of eddy currents in the peripheral
direction of the cover and the bottom.
In the assembled condition, the bottom and/or the cover may be caulked to
the shell. This is a particularly reasonably priced and reliable type of attachment.
Prior to connecting the sheet metal parts, the magnet coil may be introduced into
the shell without problems, so that by the caulking process a preassembled unit
consisting of the bottom, the cover, the shell and the magnet coil is provided in a
very simple manner.

-3-
ln a further embodiment, the shell of the magnet housing has at least one
aperture, and the magnet coil is potted or is coated or encased by injection-
molding. A liquid plastic mass is introduced through this aperture into the magnet
housing, so that the magnet coil is embedded in plastic material. After the curing
of the plastic mass, any gaps or cavities are closed off, and the sheet metal parts
of the magnet housing and also the magnet coil are fixed in place such that any
rattling noises in the operation of the valve can no longer occur.
The shell may have a thickness that is lower than that of the bottom, and the
bottom may have a thickness that is greater than that of the cover. This
compensates for increased magnetic reluctances, which appear primarily at the
bottom due to the non-magnetic core guide tube and the air gap to the movable
magnet armature, by greater sheet metal part thicknesses. Owing to the
multilayer structure of the sheet metal parts, the sheet metal part thickness can
be varied very easily by varying the number of layers. The stacked sheet metal
parts of the cover, the shell and the bottom may differ with respect to the
thickness and the characteristics of the individual metal sheets, e.g. they may or
may not be insulated.
In one embodiment, the cover comprises an inner cover part and an outer
cover part, the outer contour of the inner cover part being complementary to the
inner contour of the outer cover part, so that the cover parts can be assembled
with an interlocking fit. In this context, it is not a single transformer sheet of the
cover that is referred to as a cover part, but a sheet stack built up of a plurality of
transformer sheets. This structure made up of two cover parts offers the
advantage that the inner cover part, which is comparatively more complicated to
produce, can be identically constructed and made use of even with covers of
different sizes, and the required adaptation is effected by the outer cover part,
which is less complicated to produce. Because of the interlocking connection, the
cover, which is composed of the inner and outer cover parts, essentially gives the
impression of being a one-piece cover (although built up of a plurality of sheet
metal layers), so that the magnetic flux in the plane of the cover is not impaired.
Preferably, the outer cover part is formed in the shape of a U. In this way, the
protective ground conductor connection of the inner cover part, which is

-4-
substantially responsible for the increased manufacturing expense of the inner
cover part, is well accessible, whatever the size of the cover.
Furthermore, the cover may have a covering part which covers the cover
parts in the assembled condition. In the case of larger covers, by means of this
covering part, firstly the sheet metal part thickness of the stack of sheets is
increased and secondly the base area of the cover is not separated across its
entire thickness by a joint between the inner and outer cover parts. Both factors
contribute to a reduction in the magnetic reluctance.
The invention further comprises a method of manufacturing a magnet housing
of a solenoid unit for a solenoid valve, comprising the following steps:
A) punching of metal sheets of a ferromagnetic material;
B) stacking the metal sheets to form sheet stacks which are used for
the shell, the bottom or the cover or a cover part of a magnet
housing of the solenoid unit;
C) assembling the magnet housing by producing an interlocking
connection between the cover and the shell and between the bottom
and the shell.
This method results in a simple and reasonably priced manufacture of a
magnet housing for a solenoid unit which is suitable both for direct current control
and alternating current control.
In some embodiments, the cover is assembled from an inner cover part and
an outer cover part before assembling the magnet housing, the outer contour of
the inner cover part being complementary to the inner contour of the outer cover
part. Preferably, the cover parts are then connected with an interlocking fit and/or
with a frictional fit. The interlocking connection, but also a possible frictional
engagement perpendicular to the plane of the cover provide for an unimpeded
magnetic flux in the cover plane and are simple to produce. The cover parts
having the complementary contours are preferably punched; the frictional
connection may be obtained by means of a press fit between the cover parts, for
example. When the U-shaped cover part is connected to the inner cover part with
an interlocking fit, its legs may be slightly pressed apart and deformed, so that,
when the connecting process is completed, the legs clamp the inner cover part in

-5-
place and prevent a relative movement between the cover parts perpendicularly
to the cover plane.
Subsequent to assembling the inner and outer cover parts, a covering part
may additionally be mounted to the inner and/or to the outer cover part. As the
surface area of the cover increases, the thickness of the cover may also be
adjusted, i.e. enlarged, very easily by means of such a covering part which, just
like the inner and outer cover parts, is composed of transformer sheets. The
covering part is caulked to the inner and/or to the outer cover part, for example.
In addition, the invention comprises a method of manufacturing a solenoid
unit for a solenoid valve, which includes the following steps:
A) punching of metal sheets of a ferromagnetic material;
B) stacking the metal sheets to form sheet stacks which are used for
the shell, the bottom or the cover or a cover part of a magnet
housing of the solenoid unit;
C) shaping the shell such that it can at least partially surround a magnet
coil;
D) inserting the magnet coil into the shell;
E) assembling the magnet housing by producing an interlocking
connection between the cover and the shell and between the bottom
and the shell.
In one variant of the method, the assembling of the magnet housing starts
already prior to inserting the magnet coil into the shell by already producing an
interlocking connection between the bottom and the shell or between the cover
and the shell. Accordingly, this partial step is omitted in step E.
By means of this method, the magnet housing and the magnet coil are
produced as a preassembled unit right away, with the magnet coil being located
protected in the interior of the preassembled unit. After fitting a fixed armature
antipole and a core guide tube having a movable magnet armature, the solenoid
unit is complete.
Subsequent to assembling the magnet housing, a liquid plastic mass is
preferably introduced into the assembled magnet housing through an aperture

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provided in the magnet housing, for embedding the magnet coil. The aperture is
produced e.g. by punching before or after the stacking of the metal sheets. After
the plastic mass has been introduced and has cured, the sheet metal parts of the
magnet housing and the magnet coil are fixed in place, so that no rattling noises
can occur.
Further features and advantages of the invention will be apparent from the
description below of a preferred embodiment with reference to the drawings, in
which:
- Figure 1 shows a diagrammatic section through a solenoid unit;
- Figure 2 shows a perspective view of a cover, a bottom and a shell of a
solenoid unit according to the invention;
- Figure 3 shows a perspective view of an inner cover part and an outer cover
part;
- Figure 4 shows a perspective view of a cover for a solenoid unit according to
the invention, the cover being assembled of the inner and outer cover parts
according to Figure 3; and
- Figure 5 shows a perspective exploded view of a magnet housing for a
solenoid unit according to the invention, including a multipart cover.
Figure 1 shows a solenoid unit for actuating a solenoid valve, including a
magnet coil 10 determining a coil axis A and having a winding that is received by
a bobbin 12. Further illustrated is a ferromagnetic circuit which in Figure 1
comprises a stationary magnet housing, a movable magnet armature 14 and a
stationary armature antipole 16. In the present case, the magnet housing has a
cover 18, a bottom 20 and a shell 22. In addition, a non-magnetic core guide tube
24 is provided which extends inside the magnet coil 10 between the bobbin 12
and the magnet armature 14 and armature antipole 16. The power supply to the
magnet coil 10 is effected via connections 26 led through axially, which are
likewise illustrated diagrammatically.
When the magnet coil 10 is in the de-energized condition, the magnet
armature 14 generally is biased by a spring (not shown) such that the solenoid
valve is in a desired position (opened or closed). When a current is fed to the

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magnet coil 10, an axially oriented magnetic field develops inside the magnet coil.
The magnet armature 14, the armature antipole 16 and the magnet housing (to
be more precise, the cover 18, the bottom 20 and the shell 22) form a
ferromagnetic circuit which is decisive for the force exerted on the magnet
armature 14. An axial air gap 28 exists between the magnet armature 14 and the
armature antipole 16, so that the magnet armature 14 is attracted towards the
armature antipole 16. The axial extent of the air gap 28 is equivalent to a driving
lift of the solenoid valve.
Figure 2 shows an especially advantageous embodiment of the magnet
housing, consisting of the cover 18, the bottom 20 and the shell 22. It can be
seen that the sheet metal parts of the magnet housing are built up of multiple
layers of transformer sheet metal, the cover 18 and the bottom 20 having a
plurality of layers in the axial direction and the shell 22 in the radial direction. The
orientation of the sheet stacks, that is, the axial lamination for the cover 18 and
the bottom 20 and the radial lamination of the shell 22, is selected to correspond
to the course of the magnetic flux lines, with the eddy current paths which run
perpendicularly to the magnetic flux lines being however interrupted at the layer
boundaries.
In the present embodiment, the individual layers consist of transformer sheet
metal which has a thickness of about 1 mm and may be coated with an
electrically insulating coating. As a rule, however, a mere lamination of non-
insulated transformer sheets is sufficient to largely eliminate the eddy currents as
a result of the increased electrical resistance at the layer boundaries. Figure 2
shows, by way of example, some layers for the respective housing components,
which are however only symbolic of a multilayer structure. With layer thicknesses
of 1 to 1.2 mm, the individual components preferably comprise 2 to 9 layers. For
the purpose of increasing the stability and reducing the gaps, the layers of the
components may be connected with each other, e.g. by packing of laminations,
gluing or riveting.
The thickness of the sheet metal parts of the magnet housing may be
appropriately selected very easily by varying the number of layers. As a rule, the
bottom 20, for example, includes more layers than the cover 18 or the shell 22, in
order to at least partly compensate for the increased magnetic reluctance in the

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region of the bottom 20 caused by the non-magnetic core guide tube 24 and the
air gap between the core guide tube 24 and the movable magnet armature 14.
Tabs 32 on the shell 22 may be inserted into recesses 30 provided in the
cover 18 and the bottom 20. The cover 18 and the bottom 20 are each connected
with the shell 22 by assembling the parts and by caulking the tabs 32. The
magnet coil 10 may be inserted axially without problems prior to the assembly of
the magnet housing and is enclosed inside the magnet housing after caulking of
the tabs 32. According to another embodiment, the cover 18 and/or the bottom 20
are welded or screwed to the shell 22,
Figure 2 shows that the shell 22 is provided with a plurality of apertures 36
through which a liquid plastic mass is introduced after insertion of the magnet coil
10 and assembly of the magnet housing, in order to embed the magnet coil 10
and fix it in place. Commonly used methods of embedding the magnet coil 10
include encasing or coating by injection-molding, or potting. The apertures 36 are
preferably provided at places where the effect of the ferromagnetic circuit is least
impaired. The cover 18 or the bottom 20 may, of course, also have apertures for
this purpose.
The cover 18 and the bottom 20 each have a central opening for insertion of
the core guide tube 24 with the magnet armature 14 or of the armature antipole
16. Furthermore, the cover 18 and the bottom 20 each have a radial slot 34 which
is continuous from the central opening as far as to the outer periphery, the slot
reducing formation of eddy currents in the peripheral direction of the cover 18 and
the bottom 20.
Depending on the respective production series of the solenoid valve, the
individual sheet metal parts of the magnet housing may exhibit special features.
For example, in Figure 2 the substantially circular cover 18 is cut off along a
chord so as to make it easier for the connections 26 of the magnet coil 10 to be
led through axially. The extent of the shell 22 in the peripheral direction is
essentially dependent on the production series of the valve and merely needs to
ensure sufficient magnetic flux. Preferably, however, the multilayer shell 22
surrounds at least half of the magnet coil 10 and, in an extreme case, encloses it
entirely, but in the latter case at least one axially extending slot should be
provided to reduce an occurrence of eddy currents in the peripheral direction.

-9-
Figures 3 and 4 show an inner cover part 38 and an outer, U-shaped cover
part 40 and, respectively, a cover 18 assembled of these cover parts 38, 40. For
the sake of simplicity, only a cover 18 or cover parts 38, 40 are mentioned below,
but, of course, the bottom 20 may also be a multi-piece part, assembled of
appropriate bottom parts.
The method of manufacturing the multi-piece cover 18 will now be explained
with reference to Figures 3 and 4. First, the inner and outer cover parts 38,40 are
produced in a similar manner to the bottom 20 and the shell 22 by punching,
stacking and combining ferromagnetic transformer sheets, the outer contour of
the inner cover part 38 being complementary to the inner contour of the outer
cover part 40. To form a protective ground conductor connection 42 on one side
of the inner cover part 38, some of the transformer sheets are provided with
recesses and others with projections across the height of the cover 18, resulting
in a complex contour the manufacturing of which involves increased tool costs.
Because of this higher manufacturing expense, all the embodiments use an
identically constructed inner cover part 38 with the protective ground conductor
connection 42. In the case of small magnet housings, the inner cover part 38
constitutes the whole cover 18, whereas in the case of larger magnet housings,
the U-shaped outer cover part 40, which is simple to produce, is connected with
the inner cover part 38 with an interlocking and/or a frictional fit. In that case, the
recesses 30 of the inner cover part 38 serve for the interlocking connection with
corresponding projections 44 of the outer cover part 40, rather than for a
connection with the shell 22 (cf. Figure 2). For an improved interlocking and/or
frictional connection between the cover parts 38, 40, additional cooperating
grooves and projections may be provided, which are illustrated in dashed lines in
Figure 4.
Figure 5 shows an exploded view of a magnet housing having a cover 18
made up of multiple pieces. In order to be able to also adjust the sheet metal part
thickness of the cover 18 in the case of larger covers 18, a covering part 46 is
provided; this covering part 46 covers the cover parts 38, 40, i.e. the base area of
the covering part 46 is the same as the base area of the inner and outer cover
parts 38, 40 when in the assembled condition. In this case the shell 22, the outer
cover part 40 and the covering part 46 are caulked to each other using the tabs
32 of the shell 22 which, in comparison with those in Figure 2, are somewhat

-10-
longer. In addition, the covering part 46 may also be firmly connected with the
inner cover part 38. To reduce eddy currents in the peripheral direction of the
cover 18, the covering part 46 is likewise provided with a radial slot 34.

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Claims
1. A solenoid unit for a solenoid valve, comprising a magnet coil (10) and a
ferromagnetic circuit which surrounds the magnet coil (10) and includes a
stationary magnet housing and a movable magnet armature (14), characterized
in that the magnet housing is assembled of a cover (18), a shell (22) and a
bottom (20) in the form of multilayer transformer sheet metal parts.
2. The solenoid unit according to claim 1, characterized in that the
transformer sheet metal parts are punched and, if required, bent.

3. The solenoid unit according to either of the preceding claims,
characterized in that the transformer sheet metal parts have a plurality of layers,
these layers being connected to each other.
4. The solenoid unit according to any of the preceding claims, characterized
in that the cover (18) and/or the bottom (20) have/has a central opening.
5. The solenoid unit according to claim 4, characterized in that the cover (18)
and/or the bottom (20) have/has a radial slot (34) that is continuous from the
central opening up to the outer periphery.
6. The solenoid unit according to any of the preceding claims, characterized
in that in the assembled condition, the cover (18) and/or the bottom (20) are/is
caulked to the shell (22).
7. The solenoid unit according to any of the preceding claims, characterized
in that the shell (22) has at least one aperture (36) and the magnet coil is potted
or is coated or encased by injection-molding.
8. The solenoid unit according to any of the preceding claims, characterized
in that the shell (22) has a thickness that is lower than that of the bottom (20).
9. The solenoid unit according to claim 8, characterized in that the bottom
(20) has a thickness that is greater than that of the cover (18).
10. The solenoid unit according to any of the preceding claims, characterized
in that the cover (18) comprises an inner cover part (38) and an outer cover part
(40), the outer contour of the inner cover part (38) being complementary to the

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inner contour of the outer cover part (40), so that the cover parts (38, 40) can be
assembled with an interlocking fit.
11. The solenoid unit according to claim 10, characterized in that the outer
cover part (40) is formed in the shape of a U.
12. The solenoid unit according to claim 10 or 11, characterized in that the
cover (18) has a covering part (46) which covers the cover parts (38, 40) in the
assembled condition.
13. A method of manufacturing a magnet housing of a solenoid unit for a
solenoid valve, comprising the following steps:
punching of metal sheets of a ferromagnetic material;
stacking the metal sheets to form sheet stacks which are used for the shell
(22), the bottom (20) or the cover (18) or a cover part of a magnet housing of the
solenoid unit;
assembling the magnet housing by producing an interlocking connection
between the cover (18) and the shell (22) and between the bottom (20) and the
shell (22).
14. The method according to claim 13, characterized in that prior to step C),
the cover (18) is assembled from an inner cover part (38) and an outer cover part
(40), the outer contour of the inner cover part (38) being complementary to the
inner contour of the outer cover part (40).
15. The method according to claim 14, characterized in that the cover parts
(38, 40) are connected with an interlocking fit and/or with a frictional fit.
16. The method according to claim 14 or 15, characterized in that subsequent
to assembling the inner and outer cover parts (38, 40), a covering part (46) is
mounted to the inner and/or to the outer cover part (38, 40).
17. A method of manufacturing a solenoid unit for a solenoid valve,
comprising the following steps:
A) punching of metal sheets of a ferromagnetic material;

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B) stacking the metal sheets to form sheet stacks which are used for
the shell (22), the bottom (20) or the cover (18) or a cover part of a
magnet housing of the solenoid unit;
C) shaping the shell (22) such that it can at least partially surround a
magnet coil (10);
D) inserting the magnet coil (10) into the shell (22);
E) assembling the magnet housing by producing an interlocking
connection between the cover (18) and the shell (22) and between
the bottom (20) and the shell (22).
18. The method according to claim 17, characterized in that the assembling of
the magnet housing starts already prior to inserting the magnet coil (10) into the
shell (22) by producing an interlocking connection between the bottom (20) and
the shell (22) or between the cover (18) and the shell (22).
19. The method according to claim 17 or 18, characterized in that subsequent
to step E), a liquid plastic mass is introduced into the assembled magnet housing
through an aperture (36) provided in the magnet housing, for embedding the
magnet coil (10).

The invention relates to a solenoid unit for a solenoid valve, including a
magnet coil (10) and a ferromagnetic circuit which surrounds the magnet coil (10)
and comprises a stationary magnet housing, a movable magnet armature (14)
and, if required, an armature antipole (16), the magnet housing being assembled
of a cover (18), a shell (22) and a bottom (20) in the form of multilayer
transformer sheet metal parts.
The invention further relates to a method of manufacturing such a solenoid
unit and to a method of manufacturing a magnet housing for such a solenoid unit.

"A SOLENOID UNIT FOR A SOLENOID VALUE AND THE METHOD OF MANUFACTURING THE SOLENOID UNIT"

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