Magnet assembly for a magnet valve

State of the art

p0001The invention relates to a magnetic module for a magnetic valve according to the preamble of claim 1.

p0002For example, a solenoid valve is used to control the opening and closing movement of an injector member of a fuel injector. The solenoid valve comprises a magnetic module.

p0003Through the <patcit id="pcit0001" dnum="DE19712591A1"><text>DE 197 12 591 A1</text></patcit> A magnetic assembly for a solenoid valve is known. This includes an inner pole and an outer pole as well as a coil. The coil is arranged between the inner pole and the outer pole and surrounds the inner pole. The electrical insulation between the coil and the inner pole is not detailed in the simplified depiction and thus obviously executed as standard. This results in a coil carrier made of electrically insulating material, in which the coil is received. The magnet assembly is undesirably radially increased by the coil carrier.

p0004The disadvantage of the magnetic assembly, as is known from the prior art, is its large installation space, especially for use in fuel injectors. The magnetic assembly is diametrical for the solenoid valve. In addition, due to the winding carrier made of insulating material, a limited thermal conductivity results. This can lead to overheating of the coil, especially in the case of fast-switching solenoid valves. In addition, only a small number of turns is possible due to the desired small installation space and the dimensions of the bobbin carrier. An increase in the number of windings would require a larger diameter of the coil and thus lead to a larger magnet assembly.

Disclosure of the invention

p0005In a magnet assembly according to the invention for a magnetic valve comprising an inner pole, an outer pole and a coil, the coil being arranged between the inner pole and the outer pole, the coil is wound directly onto the inner pole. By winding the coil directly onto the inner pole , The space occupied by the bobbin carriers in the solutions known from the prior art is saved. As a result, the mounting space of the magnetic module can be reduced. Moreover, in order to increase the magnetic force, it is possible to apply a larger number of windings with the same installation space.

p0006In order to prevent a short circuit being produced, when the inner pole is made of an electrically conductive material, the inner pole is coated with an electrically insulating coating on the side facing the coil. The coating is preferably a parylene coating. This is an inert, hydrophobic, optically transparent, polymer coating, which ensures very good electrical insulation with high dielectric strength and low dielectric constant. The coating is microporous free from a layer thickness of 0.2 μm. The coating is generally applied in vacuo by condensation from the gas phase. This also achieves regions and structures which can not be coated with liquid-based processes. The layer thickness applied according to the invention to the inner pole is preferably approximately 10 μm. The coil is then wound directly onto the coating of the inner pole. Due to the small thickness of the coating, the heat generated during the switching of the magnetic valve can be dissipated via the inner pole.

p0007An outwardly projecting extension, which is pressed into the outer pole, is preferably formed on the inner pole. The outer diameter of the outwardly extending enlargement is thereby greater than the outer diameter of the coil so that a gap is formed between the coil and the outer pole when the magnetic assembly is mounted. This prevents a short circuit between the coil and the outer pole.

p0008In order to connect the coil to a voltage source, contact lugs are preferably formed on the coil. In a preferred embodiment, in order that the contact lugs can be connected to the voltage source, a recess is formed in the outwardly projecting widening at the inner pole, through which the contact lugs are guided. In this case, it is possible to provide a single recess for each contact flap or to guide all contact strips through the same recess. It is only necessary to ensure that the contact strips do not come into contact with the inner pole, the outer pole or with each other.

p0009The contact lugs are preferably connected in each case to a contact pin, by means of which the magnetic module group can be contacted with the voltage source. The contact pins are preferably electrically insulated from each other in a pin holder which is accommodated in the recess of the outwardly projecting extension of the inner pole. The electrical insulation is preferably achieved in that the rod holder is made of an electrically insulating material. If the rod holder is not made of an electrically insulating material, the latter is preferably provided with an electrically insulating coating.

p0010The magnet module according to the invention is preferably used for actuating a closing element in a magnetic valve. In a particularly preferred embodiment, the magnetic valve with the magnetic module configured according to the invention is used in a fuel injector.

drawing

p0011The invention is explained in more detail below with reference to the drawing.

p0012It shows:<dl id="dl0001"><dt>FIG</dt><dd>4 is a section through a magnetic module according to the prior art,</dd><dt>FIG</dt><dd>A perspective view of an inner pole,</dd><dt>FIG</dt><dd>4 shows a section through a magnet module according to the invention,</dd><dt>FIG</dt><dd>A plan view of an inner pole with coil and contact pins,</dd><dt>FIG</dt><dd>A perspective detail view of the electrical connection of the coil,</dd><dt>FIG</dt><dd>A perspective illustration of a wound inner pole with contact pins,</dd><dt>FIG</dt><dd>4 shows a perspective illustration of a mounted magnetic module.</dd></dl>

EXEMPLARY EMBODIMENTS

p0013<figref idrefs="f0001">FIG</figref> Shows a magnetic assembly according to the prior art.

p0014A magnetic assembly 1 according to the prior art comprises a magnetic core 2 in which a groove 3 is formed. A reel 4 is accommodated in the groove 3 and is wound on a reel carrier 5. The coil carrier 5 is preferably made from an electrically insulating material so that no electrical connection is produced between the coil 4 and the magnetic core 2. A gap 6 is formed on the outer circumference between the coil 4 and the wall of the groove 3. The gap prevents a short circuit between the coil 4 and the magnetic core 2. The voltage supply of the coil 4 is effected via contact pins 7. The contact pins 7 are connected to the coil 4 by means of contact lugs 8, which are each wound around the contact pin 7. A welding sleeve 9 is arranged around the contact strip 7 around the contact pin 7. The welding sleeve 9 prevents the contact tab 8 from being released from the contact pin 7.

p0015Additional space in the magnetic module 1 is required by the coil carrier 5 on which the coil 4 is wound. As a result, the necessary diameter of the magnetic module group 1 is increased. This is particularly disadvantageous when solenoid valves have to be used whose construction space is as small as possible.

p0016In <figref idrefs="f0002">FIG</figref> An inner pole designed according to the invention is shown in perspective.

p0017An expansion 12 which projects outwards is formed on an inner pole 11 constructed according to the invention. A recess 13 is formed in the outwardly projecting extension 12. Furthermore, the inner pole 11 comprises a cylindrical body 14,<figref idrefs="f0002">FIG</figref> Not shown coil. In order to avoid a short circuit between the coil and the cylindrical body 14, the cylindrical body 14 is coated. The coating is preferably carried out with parylene. As a result, a coating with a thickness of approximately 10 μm is already sufficient to ensure sufficient electrical insulation. Due to the small thickness of the coating, however, the thermal insulation effect is only very small so that the heat generated during operation of the magnetic module in the coil can be dissipated via the internal pole. In the interior of the cylindrical body 14, a bore 15 is provided, in which, for example, a valve spring can be guided when the magnetic module is used for actuating a magnetic valve.

p0018<figref idrefs="f0003">FIG</figref> Shows a section through a magnetic module according to the invention.

p0019A magnet assembly 20 according to the invention comprises the inner pole 11, on whose coated cylindrical body 14 a coil 21 is wound. The diameter of the coil 21 is thereby smaller than the outer diameter of the extension 12 extending outwards. In this way, a gap 23 is formed between the coil 21 and the outer pole 22 after the outer pole 22 has been pressed onto the outwardly extending enlargement 12.

p0020The coil 21 is supplied with voltage via a contact lug 24 which is connected to a contact pin 25. In order to connect the contact lug 24 to the contact pin 25, the contact lug 24 is wound around the contact pin 25 and then enclosed with a welding sleeve 26. A tight fit of the welding sleeve 26 is achieved in that it is fastened, for example, by resistance welding to the winding with which the contact flag 24 is fastened to the contact pin 25. However, any other type of fastening of the welding sleeve is also conceivable. For example, this can also be fixed by crimping. The contact pin 25 is accommodated in a pin holder 27. In order to prevent current from flowing from the contact pin 25 to the inner pole 11 or to the outer pole 22, the pin holder 27 is preferably made of an insulating material. Preferred material is plastic. However, it is also possible to form the stator holder 27 from an electrically conductive material, which is then provided with an insulating coating.

p0021In the <figref idrefs="f0003">FIG</figref> The height h of the inner pole is less than the height H of the outer pole. This makes it possible to adjust a residual air gap between the cylindrical body 14 of the inner pole 11 and an armature, which is not shown here, without the total height of the magnet assembly becoming greater than the height H of the outer pole 22.

p0022<figref idrefs="f0003">FIG</figref> Shows a plan view of an inner pole with coil and contact pins according to the invention.

p0023In the <figref idrefs="f0003">FIG</figref> It can be seen that the outer diameter d of the outwardly projecting widening 12 of the inner pole 11 is greater than the outer diameter D of the coil 21. The width of the gap 23 results from the difference between the outer diameter d of the outwardly extending widening 12 and The outer diameter D of the coil 21.

p0024Further, in the embodiment shown in FIG <figref idrefs="f0003">FIG</figref> Can be seen, that two contact pins 25 are provided for the voltage supply to the coil 21. The two contact pins 25 are accommodated in the pin holder 27. To contact the coil 21 with the contact pins 25, the contact vanes 24 are wound around the contact pins 25 and are then enclosed with the welding sleeves 26. The welding sleeves 26 are welded, for example, by resistance welding around the wound contact strips 24 to achieve a stable connection.

p0025<figref idrefs="f0004">FIG</figref> 10 shows a perspective view of the stylus holder with contact pins and contact lugs.

p0026<figref idrefs="f0004">FIG</figref> It can be seen how the contact lugs 24 are wound around the contact pins 25. By wrapping the contact pins 25 with the contact lugs 24, these are pre-fixed before the actual material or form-fitting connection. A stable electrical connection is then preferably achieved by resistance welding.

p0027In the embodiment shown here, the contact pins 25 are held in receptacles 28 in the pin holder 27. The diameter of the receptacles 28 is thereby smaller than the diameter of the contact pins 25, so that they are jammed in the receptacle 28. Tabs 29 are formed on the receptacles 28, in which the contact pins 25 are guided. At the same time, the tabs 29 serve for electrical insulation against the outer pole 22.

p0028The pin holder 27 is accommodated in the recess 13 of the extension 12 which projects outwards. To the inner pole 11 in the outer pole 22,<figref idrefs="f0004">FIG</figref> Is not shown, care must be taken that the outer surface 30 has a maximum diameter which is the same as the outwardly extending extension 12.

p0029<figref idrefs="f0005">FIG</figref> 10 shows a perspective view of an inner pole with coil and contact pins according to the invention.

p0030In the <figref idrefs="f0005">FIG</figref> It can be seen that the outer surface 30 of the rod holder 27 does not project beyond the extension 12 of the inner pole 11 projecting outwards. However, it is possible to project the outer surface 30 over the outer diameter of the coil 21 to the same extent as the outwardly extending extension 12.

p0031In the <figref idrefs="f0005">FIG</figref> The contact vanes 24 wound around the contact pins 25 are enclosed by the welding sleeves 26. As<figref idrefs="f0005">FIG</figref> The welding sleeves 26 are mounted over the windings of the contact lugs 24 so as to achieve a stable connection.

p0032<figref idrefs="f0005">FIG</figref> Shows a fully assembled magnetic assembly.

p0033In the case of the completely assembled magnetic module 20, the inner pole 11, on which the coil 21 is wound, is pressed into the outer pole 22 with the extension 12 extending outwards. By pressing the outwardly projecting extension 12 into the outer pole 22, a stable connection is achieved.

p0034To produce the magnet assembly 20 according to the invention, an inner pole 11 of a highly permeable, resistive material, preferably a soft-magnetic powder composite material, is preferably produced by pressing. In a next step, the inner pole 11 is provided with an electrically insulating coating. Parylene is preferably used for this purpose. After coating, the outwardly extending extension 12 is ground to its outer diameter d. Finally, the coil 21 is wound onto the cylindrical body 14 of the inner pole 11. After winding the coil, it is contacted with the contact pins 25, which are accommodated in the pin holder 27.

p0035The outer pole 22 is ground in a first step on the inner diameter and the abutment and stop surfaces to fit the inner pole 11. Subsequently, in a further step, the stop surface can be chromium-plated. Finally, the inner pole 11 is pressed into the outer pole 22.

p0036In a preferred embodiment, after assembling the inner pole 11 with coil 21 and contact pins 25 with the outer pole 22, the entire magnetic assembly 20 is extrusion coated with a plastic, preferably a thermoplastic, or cast with a reaction resin.