SOLENOID COIL WITH COOLING STRUCTURE AND SOLENOID VALVE WITH SUCH A SOLENOID COIL

Description

[0001] The invention relates to a magnetic coil according to the preamble of patent claim 1 and a solenoid valve with such a magnetic coil.

[0002] Solenoid coils can be used to convert electrical energy into magnetic energy. To do this, they contain a conductive wire arranged in a multitude of superimposed turns. The electrical energy supplied to the solenoid coil generates a magnetic field in the conductive wire, thereby exciting the solenoid. The wound conductive wire often encloses an iron core, which amplifies the magnetic field generated in the conductive wire. The resulting magnetic field can be used to attract and move separate components from the solenoid coil.

[0003] This mechanism is used, among other things, in the switching of solenoid valves. A solenoid valve can be switched / operated using a solenoid coil. To do this, an electrical connection of a solenoid coil is connected to a power source. With the help of the electrical energy supplied by the power source (usually in the form of a 24V voltage), the solenoid coil generates a magnetic field and thus converts the electrical energy into magnetic energy. A piston arranged in the solenoid valve is moved (attracted) by the magnetic field generated by the solenoid coil in such a way that a media inlet and a media outlet of the solenoid valve are connected to each other. In this way, the solenoid valve is opened and a medium can flow through.If the solenoid coil is no longer supplied with energy, it no longer generates a magnetic field, so the piston is no longer attracted to the solenoid coil and returns to its original position. This separates the media inlet and outlet of the solenoid valve. In this case, the solenoid valve is closed, and no medium can flow through it.

[0004] Such solenoid valves, which are switched by a magnetic coil, can serve, for example, as actuators for driving a valve body of an injection nozzle, as described, among others, in DE 10 2007 000 358 A1.

[0005] Further solenoid coils and solenoid valves are explained, among others, in CN 208 090 045 U, DE 10 2007 048 461 A1, US 5 375 738 A, JP S52-57 964 A, US 3 818 398 A, CN 212 718 297 U or DE 10 2009 054 374 A1.

[0006] DE 10 2019 004 597 A1 discloses a solenoid coil for switching a solenoid valve according to the preamble of claims 1 and 2.

[0007] It has been shown in practice that the average service life of a conventional solenoid coil is often shortened compared to its maximum achievable service life.

[0008] If the solenoid valve is switched less frequently or for shorter periods, this has a positive effect on the service life of the solenoid coil. Therefore, reducing the energy consumption of the solenoid valve is helpful in extending the service life of the solenoid coil.

[0009] For example, an amplifier with pulse width modulation can be connected to the solenoid valve. The amplifier significantly shortens the switching time of the solenoid valve. This means that the solenoid coil needs to be energized for less time. This significantly reduces the energy consumption of the solenoid coil or solenoid valve and can also extend the service life of the solenoid coil. However, this method for extending the service life of the solenoid coil is complex and expensive.

[0010] In contrast, the invention is based on the object of providing a solenoid coil whose service life can be (further) extended. In particular, the service life of the solenoid coil is to be extended in a simple and cost-effective manner.

[0011] This object is achieved with regard to the solenoid coil by the combination of features of claim 1 or 2 and with regard to the solenoid valve by the combination of features of claim 5.

[0012] Further advantageous embodiments of the invention are described in the dependent claims.

[0013] The claimed solenoid coil is designed to actuate / switch / change a valve position of a solenoid valve. The solenoid coil has a substantially cylindrical outer surface. The outer surface of the solenoid coil has a cooling structure that enlarges the outer surface.

[0014] In practice, it has been shown that the energized solenoid coil heats up due to the electrical energy supply, and this heating of the solenoid coil has a negative impact on its service life. By providing the coil's outer surface with a cooling structure, the heat generated by the solenoid coil can be easily and simply dissipated into the environment. Thus, the heating effect of the solenoid coil with a cooling structure on its outer surface is significantly reduced compared to a solenoid coil without a cooling structure. Thus, the service life of the solenoid coil with a cooling structure on its outer surface can be significantly extended compared to that of conventional solenoid coils.

[0015] In a preferred embodiment, the cooling structure is provided as a passive heat sink with cooling fins, formed separately from the outer surface of the magnetic coil.

[0016] A passive heat sink with cooling fins is simple and inexpensive to manufacture. When attached to the solenoid coil, the passive heat sink increases its surface area and dissipates the heat generated by the solenoid coil to the surroundings via its cooling fins. Because the heat sink is separate from the solenoid coil, it can be attached to or removed from the solenoid coil as needed, for example, if the area surrounding the solenoid coil does not provide sufficient space for the heat sink. The heat sink is also easy to replace.

[0017] The invention provides that the passive heat sink has a hollow cylindrical shape and the cooling fins arranged on the heat sink outer surface extend in the heat sink circumferential direction, in particular parallel to one another, and are spaced apart from one another in the heat sink longitudinal direction, in particular always at the same distance, and are interrupted by at least one longitudinal slot, in particular by two diametrically opposed longitudinal slots.

[0018] According to the invention, a first longitudinal slot is provided continuously in the radial direction, so that the heat sink wall surface is continuously interrupted in the longitudinal direction at this point. A second longitudinal slot, diametrically opposite the first longitudinal slot, is not provided continuously in the radial direction, but is provided as a notch on the heat sink outer wall extending in the heat sink longitudinal direction, in particular over the entire heat sink length, and serves as a predetermined bending point. When the hollow cylindrical heat sink is arranged on the magnetic coil, the first longitudinal slot is widened and the heat sink is bent open at the predetermined bending point defined by the second longitudinal slot. Once the heat sink is arranged on the magnetic coil, the heat sink returns to its original hollow cylindrical shape.

[0019] It is desirable for the cooling fins to be distributed across the entire height / length of the hollow cylindrical heat sink. This arrangement of the cooling fins on the passive heat sink allows for an optimal increase in the surface area for dissipating the heat generated by the magnetic coil.

[0020] Ideally, the height / length of the hollow cylindrical heat sink should be (approximately) the same as the height / length of the cylindrical solenoid coil. This allows the entire outer surface of the solenoid coil to be covered with cooling fins, ensuring optimal heat conduction via these cooling fins.

[0021] Furthermore, it is advantageous if the inner dimension of the hollow cylindrical passive heat sink is smaller than (undersized to) an outer dimension of the magnetic coil, so that the passive heat sink can be press-fitted onto the coil outer surface when arranged thereon and the at least one (the first) longitudinal slot widens in the process.

[0022] This means that the inner dimension, in particular the inner diameter, of the hollow-cylindrical heat sink, is at least slightly smaller than the outer dimension, in particular the outer diameter, of the cylindrical magnetic coil. Furthermore, the at least one longitudinal slot (and alternatively or additionally due to the material elasticity of the hollow-cylindrical heat sink) makes it possible to reversibly expand the heat sink for placement on the magnetic coil. Once the heat sink is positioned on the magnetic coil, the restoring force inherent in the heat sink material acts in such a way that the heat sink "encloses" the magnetic coil and is thus firmly attached to it. Due to these features, the heat sink can be easily and securely positioned on the magnetic coil.

[0023] In an alternative embodiment, the passive heat sink has a (semi-)circular arc shape, and the cooling fins arranged on the heat sink's outer surface extend in the heat sink's longitudinal direction and are spaced apart from one another in the heat sink's circumferential direction, in particular always at the same distance. The cooling fins are advantageously distributed over at least part of the heat sink's circumference.

[0024] Ideally, the cooling fins extend the entire height / length of the circular heat sink, but are only distributed over a portion of the heat sink's circumference. When this passive heat sink is positioned on the solenoid coil, the cooling fins' arrangement allows them to dissipate heat from the solenoid coil to its surroundings particularly effectively.

[0025] Ideally, the height / length of the circular heat sink is less than the height / length of the cylindrical solenoid coil. This means that the passive heat sink covers only a portion of the coil's outer surface. Such circular heat sinks can be sufficient for cooling the solenoid coil in certain applications and are more cost-effective and take up less space than, for example, a passive hollow-cylindrical heat sink, which covers the entire outer surface of the coil.

[0026] It can be advantageous for the circular-arc passive heat sink to have no cooling fins in its circumferential end regions. In this case, these end regions can be more easily gripped and positioned on the magnetic coil.

[0027] Furthermore, according to the invention, the inner dimension of the (semi-)circular arc-shaped passive heat sink is smaller than (undersized to) an outer dimension of the magnetic coil, so that the passive heat sink can be press-fitted onto the coil outer surface when arranged thereon.

[0028] This means that the inner dimensions, in particular the inner radius of the (semi-)circular heat sink, are at least slightly smaller than the outer dimensions, in particular the outer radius, of the cylindrical magnetic coil. Due to the material elasticity of the (semi-)circular heat sink, the heat sink can be reversibly expanded for placement on the magnetic coil. Once the heat sink is positioned on the magnetic coil, the restoring force inherent in the heat sink material acts in such a way that the heat sink "encloses" the magnetic coil and is thus firmly attached to it. Due to these features, the heat sink can be easily and securely positioned on the magnetic coil.

[0029] In particular, the hollow cylindrical heat sink covering the entire outer surface of the coil as well as the circular arc-shaped heat sink covering only part of the outer surface of the coil are made of metal.

[0030] Another example provides that the cooling structure is designed as an externally powered heat sink that is actively ventilated (actively cooled) separately from the outer surface of the magnetic coil.

[0031] If the heat sink mounted on the solenoid coil is actively ventilated (hereinafter also referred to simply as an active heat sink), it can dissipate more heat from the solenoid coil to the environment than a passive heat sink. Installing an active heat sink on the solenoid coil is particularly useful when excessive heating of the solenoid coil is a concern.

[0032] It is further conceivable that the actively ventilated, externally powered heat sink comprises a fan which is supplied with energy from an energy source which is formed at least separately from the magnetic coil.

[0033] If the active heat sink has a fan, the active heat sink can cool the magnetic coil particularly effectively.

[0034] In a particularly preferred example, the cooling structure is designed as an energy-self-supplying heat sink that is actively ventilated separately from the outer surface of the magnetic coil.

[0035] Energy self-sufficient here means that the active heat sink arranged on the magnetic coil receives its energy from the magnetic coil.

[0036] It is preferred if the actively ventilated, self-powered heat sink has a fan that is supplied with lost energy, particularly in the form of (waste) heat, from the magnetic coil. Thus, the thermal energy from the magnetic coil can be used to drive the fan of the active heat sink. Such a self-powered active heat sink is therefore extremely energy-efficient, and no power supply from an external energy source is required.

[0037] Preferably, the actively ventilated, self-powered heat sink (particularly its fan) is supplied with a power signal from the solenoid coil. This means that the solenoid valve or solenoid coil and the actively ventilated, self-powered heat sink (or its fan) are simultaneously activated via a control signal, which places the solenoid valve in an active / switching state.

[0038] It is advantageous if a thermocouple or a thermoelectric generator is arranged between the magnetic coil and the heat sink, in particular between the magnetic coil and the fan, which converts the lost energy from the magnetic coil into an energy form, in particular into an electrical voltage, which is fed to the fan of the heat sink.

[0039] With the help of the thermocouple or the thermoelectric generator, electrical energy (voltage) can be generated from the waste heat of the magnetic coil, which is then fed to the active, energy-self-sufficient heat sink to drive its fan.

[0040] In principle, it is conceivable that the actively ventilated (externally powered or self-powered) heat sink, especially its fan, is only active (the fan rotates) when the solenoid valve or solenoid coil is active. However, it is equally possible that the actively ventilated (externally powered or self-powered) heat sink also cools when the solenoid valve or solenoid coil is inactive. Thus, it is possible for the actively ventilated heat sink to only cool when the solenoid valve is active, and for the actively ventilated heat sink to cool (continuously) regardless of the solenoid valve's activity state.

[0041] A further embodiment provides that the outer surface of the magnetic coil itself is at least partially, in particular completely, designed as a cooling structure in the form of cooling fins.

[0042] This has the advantage that the cooling structure is integrated into the solenoid coil from the outset and therefore does not have to be placed on the solenoid coil in an additional assembly step.

[0043] Advantageously, the magnetic coil is designed as a hollow cylinder, which integrally comprises, on its outer surface, in particular over the entire outer surface, a plurality of cooling fins extending in the longitudinal direction of the hollow cylinder, in particular parallel to one another, and projecting outward from the outer surface of the casing. The cooling fins are spaced apart from one another in the circumferential direction, in particular always at the same distance from one another.

[0044] This design of the outer surface of the magnetic coil is very advantageous with regard to heat dissipation.

[0045] Alternatively, it is conceivable that the cooling fins, which are part of (integral with) the outer surface of the magnetic coil, run in the circumferential direction of the substantially cylindrical magnetic coil and are spaced apart from one another in its longitudinal direction.

[0046] The solenoid valve according to the invention has a previously described solenoid coil. Furthermore, the solenoid valve has at least one valve body, a valve seat, and a closing element. The solenoid coil brings the closing element into contact with the valve seat and terminates contact between the closing element and the valve seat to actuate the solenoid valve at least between a closed and an open position.

[0047] Because the solenoid coil has a cooling structure on its outer surface that enlarges the surface, at least the majority of the (waste) heat generated by the solenoid coil is dissipated into the environment, and the solenoid coil barely heats up. Thus, the service life of this solenoid coil is increased compared to one without a cooling structure, and the solenoid coil according to the invention can reliably switch the solenoid valve according to the invention.

[0048] Several embodiments of a magnetic coil according to the invention and of a solenoid valve with such a magnetic coil are shown in the figures.

[0049] They show: Fig. 1 a perspective view of a magnetic coil; Fig. 2 a plan view of a base of the magnetic coil; Fig. 3 a perspective view of a passive heat sink according to a first embodiment; Fig. 4 a perspective view of a passive heat sink according to a second embodiment; Fig. 5 a perspective view of an actively ventilated heat sink according to a third embodiment; Fig. 6 a plan view of a heat conversion element arranged between a magnetic coil and the heat sink according to the third embodiment; Fig. 7 a perspective view of a magnetic coil whose outer surface is designed as a cooling structure; and Fig. 8 a perspective view of a solenoid valve connected to two solenoid coils.

[0050] Fig. 1 is a perspective view of a solenoid coil 1. The solenoid coil 1 is designed here as a hollow cylinder. The solenoid coil 1 has an outer surface 2, to which a heat sink can be attached, enlarging this outer surface 2, or which itself can be designed as a cooling structure enlarging its surface. An electrical connection 4 protrudes from the outer surface 2. Via the electrical connection 4, the solenoid coil 1 can be connected to an (electrical) energy source that can excite the solenoid coil 1. On one base surface of the hollow cylindrical solenoid coil 1, which is closer to the electrical connection 4, a pin / mandrel 6 is formed. The solenoid coil 1 can be connected to a solenoid valve via the mandrel 6. The solenoid coil 1 is in Fig. 1 shown without cooling structure.

[0051] Fig. 2 is a plan view of the base of the solenoid coil 1, which has the pin / mandrel 6. The electrical connection 4 is covered with a protective cap 8, which is intended to prevent damage / deformation of the electrical connection 4. The protective cap 8 is removed before the electrical connection 4 is connected to a power source.

[0052] Fig. 3 is a perspective view of a passive heat sink 10 according to a first embodiment. This heat sink 10 is designed as a hollow cylinder, the inner diameter of which is dimensioned such that it can be slipped over the magnetic coil 1 and clamped onto it. Thus, a force-fit connection exists between the heat sink 10 and the magnetic coil 1.

[0053] The heat sink 10 is formed separately from the magnetic coil 1. The heat sink 10 is designed as a passive cooling structure and has a plurality of cooling fins 12. The cooling fins 12 are formed as part of the outer surface of the heat sink 10 and run parallel to one another in its circumferential direction. The cooling fins 12 are arranged at a distance from one another in the circumferential direction over the entire height of the hollow cylindrical heat sink 10. Two diametrically opposed first and second longitudinal slots 13a and 13b, which extend over the entire height of the heat sink 10, interrupt the cooling fins 12. The first longitudinal slot 13a is continuous in the radial direction, so that it breaks through the heat sink wall. The second longitudinal slot 13b is provided in the radial direction as a notch in the heat sink outer wall and defines a predetermined bending point of the heat sink 10.The first longitudinal slot 13 widens when the heat sink 10 is arranged on the magnetic coil 1, and the heat sink 10 bends at the predetermined bending point, increasing its radius, to facilitate the arrangement of the heat sink 10 on the magnetic coil 1. In addition, the first and second longitudinal slots 13a, 13b serve to save material on the heat sink 10 and make the heat sink 10 lighter.

[0054] If the heat sink 10 is arranged around the magnetic coil 1 and the magnetic coil 1 becomes warm, the heat is conducted outward via the cooling fins 12 and dissipated into the environment. Thus, the magnetic coil 1 is passively cooled by conduction with the help of the heat sink 10. It is advantageous if the heat sink 10 has a recess (not shown) that is dimensioned to at least partially surround the electrical connection 4 of the magnetic coil 1 when the heat sink 10 is arranged on the outer surface 2 of the magnetic coil 1. The height of the heat sink 10 advantageously corresponds to the height of the magnetic coil 1.

[0055] Fig. 4 is a perspective view of a passive heat sink 14 according to a second exemplary embodiment. This heat sink 14 is designed as an (extruded) circular arc, wherein the radius of the circular arc is dimensioned such that the heat sink 14 can be arranged on the magnetic coil 10, in particular can be clamped onto it. A plurality of cooling fins 16 protrude outward from the outer surface of the heat sink 14 and extend over the entire height of the heat sink 14 in its vertical direction. The cooling fins 16 are spaced apart from one another in a circumferential direction by a predetermined distance, optionally always by the same distance, and are distributed over the circumference of the heat sink 14. However, the cooling fins 16 are arranged only on a part of the outer circumferential surface of the heat sink 14 and not distributed over its entire outer circumferential surface. The cooling fins 16 preferably all have the same dimensions.With its cooling fins 16, the heat sink 14 is designed as a passive cooling structure and, when placed on the magnetic coil 1, dissipates heat from the magnetic coil 1 to the outside. The heat sink 14 is dimensioned such that it covers only a portion of the outer surface 2 of the magnetic coil 1. In particular, the height of the heat sink 14 is less than the height of the magnetic coil 1.

[0056] Furthermore, Fig. 5 A perspective view of an actively ventilated heat sink 18 according to a third exemplary embodiment. The heat sink 18 has a lower and an upper component 20, 22. The lower component 20 is constructed similarly to the heat sink 14 according to the second exemplary embodiment. However, here the cooling fins 21 of the lower component 20 have different depths from one another and are designed such that they form a type of flat plateau. The upper component 22, which is designed as a fan, is arranged on this plateau. The lower and upper components 20, 22 can be connected to one another via a clamping connection, i.e., in a force-fitting manner. Alternatively, the lower and upper components can also be connected to one another in a form-fitting or material-fitting manner. The fan 22 is powered by energy and has a propeller element (not shown here).If energy is supplied to the fan 22, the propeller element is set in motion, in particular in a rotational movement, and thereby generates an air movement.

[0057] The heat sink 18 is arranged above the lower component 20 on the outer surface 2 of the magnetic coil 1. The inner radius of the lower component 20 is dimensioned such that the lower component 20 can be arranged on the outer surface 2 of the magnetic coil 1, in particular can be clamped onto it (according to the same principle as the passive, circular-arc-shaped heat sink 14). A force-locking connection thus exists between the heat sink 18 and the magnetic coil 1. If the heat sink 18 is arranged on the outer surface 2 of the magnetic coil 1 and the magnetic coil 1 or its outer surface 2 becomes warm, the lower component 20 conducts the heat from the magnetic coil 1 via the cooling fins 21 to the fan 22. The propeller element in the fan 22 moves (rotates) and thus distributes the warm air to the environment. The heat sink 18 thus acts as an actively ventilated heat sink that can dissipate the heat generated by the magnetic coil 1 by convection.

[0058] The fan 22 may also have a frame structure 23. This is connected to the fan 22 in a form-fitting manner (via fastening means, e.g., screws). The frame structure 23 increases the stability of the fan 22 and protects it from impacts, etc.

[0059] The heat sink 18 has an electrical connection (not shown here) through which the fan 22 receives energy. In one embodiment, the fan 22 can receive energy from an external energy source. In another embodiment, a heat conversion element can convert the (waste) heat from the magnetic coil 1 into energy, in particular electrical energy, that can be used by the fan 22. In this case, the fan 22 receives the energy required for moving its propeller element directly from the magnetic coil 1 via its electrical connection. If a heat conversion element is provided on the magnetic coil 1 and / or the heat sink 18, the cooling structure according to the invention is accordingly designed as a heat sink 18 that is actively ventilated separately from the outer surface 2 of the magnetic coil 1 and is self-sufficient in terms of energy.

[0060] Fig. 6 is a plan view of a heat conversion element, which here is embodied as a thermocouple 24. The thermocouple 24 comprises a metal. However, the heat conversion element can alternatively be embodied as a thermoelectric generator, which comprises semiconductor materials (similar to a Peltier element) instead of a metal.

[0061] The thermocouple 24 is arranged between the magnetic coil 1 and the heat sink 18 according to the third exemplary embodiment. As already described above, the thermocouple 24 receives the heat (energy) from the magnetic coil 1 and converts it into electrical energy. The thermocouple 24 has an electrical connection 25. This is connected to the electrical connection of the heat sink 18 so that the heat sink 18 can receive the electrical energy converted by the thermocouple 24. This electrical energy can then be used to operate the fan 22. In an advantageous embodiment (not shown here), the thermocouple 24 is arranged on the plateau between the lower component 20 and the fan 22.

[0062] Fig. 7 is a perspective view of a magnetic coil 1, the outer surface 2 of which is itself designed as a cooling structure. The outer surface 2 is designed as a plurality of cooling fins 26 that extend along the height direction of the magnetic coil 1 over its entire height. The cooling fins 26 are arranged circumferentially at, in particular, the same distances from one another and are evenly distributed over the entire outer circumference of the magnetic coil 1.

[0063] Fig. 8 is a perspective view of a solenoid valve 28 connected to two solenoid coils 1. The solenoid valve 28 is designed as a cuboid and has a solenoid coil 1 on each of its two short end faces. The solenoid coils 1 do not have a cooling structure in this illustration. However, it is conceivable that one of the heat sinks 10, 14, or 18 according to the first, second, or third embodiment can be connected to the solenoid coil 1. Alternatively, the outer surface 2 of the solenoid coils 1 itself could be designed as a passive cooling structure, as shown in Fig. 7 is shown.

[0064] The electrical connections 4 of the two solenoid coils 1 are not shown here as being connected to a power source. However, if the solenoid valve is to be operated / actuated / switched, the electrical connection 4 of each solenoid coil 1 is connected to a power source. The electrical energy supplied by the power source causes the solenoid coil 1 to generate a magnetic field / be excited, thereby converting the electrical energy into magnetic energy. A piston (not shown) arranged in the solenoid valve 28 is moved by the magnetic field generated by the solenoid coil such that a media inlet and a media outlet (both not shown) of the solenoid valve 28 are connected to one another. In this case, the solenoid valve 28 is open and a medium can flow through.If no more energy is supplied to the solenoid coil 1, the solenoid coil 1 no longer generates a magnetic field, so the piston returns to its original position, separating the media inlet and outlet of the solenoid valve 28 from each other again. In this case, the solenoid valve 28 is closed, and no medium can flow through the solenoid valve 28.

[0065] The solenoid coils 1 can be inserted via the pin / mandrel 6 into a corresponding recess (not shown) provided on the solenoid valve 28 and thus connected to it. Fig. 8The solenoid coils 1 also each have an auxiliary actuation device 30. The auxiliary actuation device 30 is provided at the free end of the solenoid coil 1. The auxiliary actuation device 30 allows the solenoid valve 28 to be switched even when the solenoid coil 1 is not energized / does not generate a magnetic field. The solenoid valve 28 can therefore be switched directly manually via the auxiliary actuation device 30.

[0066] In an alternative embodiment, the solenoid valve 28 is connected to only one solenoid coil 1. List of reference symbols:

[0067] 1Solenoid coil 2Outer surface (of the solenoid coil) 4Electrical connection (of the solenoid coil) 6Pin / mandrel 8Protective cap 10Heat sink 12Cooling fins 13aFirst longitudinal slot 13bSecond longitudinal slot 14Heat sink 16Cooling fins 18Heat sink 20Lower component 21Cooling fins 22Upper component / fan 23Frame structure 24Thermocouple / thermoelectric generator 25Electrical connection (of the thermocouple / thermoelectric generator) 26Cooling fins 28Solenoid valve 30Auxiliary override

Claims

1. Magnetic coil (1) for switching a solenoid valve, having a substantially cylindrical coil outer surface (2), wherein the magnetic coil (1) on its outer surface (2) has a cooling structure which enlarges the outer surface, the cooling structure is provided as a passive heat sink (10) which has cooling fins (12) and is formed separately from the outer surface (2) of the magnetic coil (1), the passive heat sink (10) has a hollow cylindrical shape and the cooling fins (12) disposed on the outer surface of the heat sink extend in the circumferential direction of the heat sink and are mutually spaced apart in the longitudinal direction of the heat sink and are interrupted by at least one longitudinal slot (13a), in particular by two diametrically disposed longitudinal slots (13a, 13b), characterized in that the inner dimension of the hollow-cylindrical passive heat sink (10) is smaller than an outer dimension of the magnetic coil (1), so that the passive heat sink (10) during disposal on the coil outer surface (2) can be press-fitted onto the latter, and the at least one longitudinal slot (13a) widens in the process.

2. Magnetic coil (1) for switching a solenoid valve, having a substantially cylindrical coil outer surface (2), wherein the magnetic coil (1) on its outer surface (2) has a cooling structure which enlarges the outer surface, the cooling structure is provided as a passive heat sink (10) which has cooling fins (16) and is formed separately from the outer surface (2) of the magnetic coil (1), characterized in that the passive heat sink (14) has an arcuate shape and the cooling fins (16) disposed on the outer surface of the heat sink extend in the longitudinal direction of the heat sink and are mutually spaced apart in the circumferential direction of the heat sink, and in that the inner dimension of the arcuate passive heat sink (14) is smaller than an outer dimension of the magnetic coil (1), so that the passive heat sink (14) during disposal on the coil outer surface (2) can be press-fitted onto the latter.

3. Magnetic coil (1) according to Claim 1 or 2, characterized in that the outer surface (2) of the magnetic coil (1) per se is designed at least partially, in particular completely, as a cooling structure in the form of cooling fins.

4. Magnetic coil (1) according to Claim 3, characterized in that the magnetic coil (1) is designed as a hollow cylinder, which has on its shell outer surface (2), in particular on the entire shell outer surface (2), a multiplicity of integral cooling fins (26) which extend in the longitudinal direction of the hollow cylinder and are mutually spaced apart in the circumferential direction of the hollow cylinder and protrude outwards from the shell outer surface (2).

5. Solenoid valve (28) having at least one valve body, a valve seat, a locking element and a magnetic coil (1) according to one of the preceding claims, the latter bringing the locking element into contact with the valve seat and terminating a contact between the locking element and the valve seat, so as to activate the solenoid valve (28) at least between a closed and an opened position.