Magnetic field sensor and method for manufacturing a magnetic field sensor

Abstract

Magnetic field sensor and method of manufacturing a magnetic field sensor This magnetic field sensor comprises a sensor head, the sensor head having a printed circuit board terminal portion (18) of a printed circuit board (12) as well as a Hall element (22) and a ring magnet (16) on the printed circuit board terminal portion (18). The ring magnet (16) surrounds the printed circuit board end portion (18), and the Hall element (22) is partially arranged inside the ring magnet (16). The printed circuit board end portion (18), comprising the ring magnet (16) and the Hall element (22), is arranged in an encapsulation housing (14) made as an injection-molded plastic part. The encapsulation housing (14) permanently fixes the ring magnet (16) relative to the Hall element (22). (See Figure 7 for abbreviations.)

Description

Title of the invention: Magnetic field sensor and method for manufacturing a magnetic field sensor

[0001] Magnetic field sensor and method for manufacturing a magnetic field sensor

[0002] The invention relates to a magnetic field sensor comprising a sensor head, the sensor head having a printed circuit board terminal portion, as well as a Hall effect sensor and a ring magnet on the printed circuit board terminal portion. The invention further relates to a method for manufacturing a magnetic field sensor.

[0003] A magnetic field sensor of the aforementioned type is known, for example, as a speed sensor for a speed recorder in a motor vehicle, particularly in a commercial vehicle. The magnetic field sensor is screwed into a transmission housing in the vehicle's drivetrain and detects the movement of a gear in the transmission using its sensor head. For accurate operation of the magnetic field sensor, precise positioning of the sensor head, in particular the Hall effect element and the ring magnet of the sensor head, relative to the transmission gear is required. To ensure this, a very precise arrangement of the Hall effect element and the ring magnet in the sensor head is necessary during the manufacturing of the magnetic field sensor.

[0004] The object of the invention is to provide a magnetic field sensor of the aforementioned type, which can be manufactured in a simplified manner and exhibits high measurement accuracy. The object of the invention is further to provide a method for manufacturing a magnetic field sensor that allows for simplified manufacturing of a magnetic field sensor exhibiting high measurement accuracy.

[0005] The first objective is achieved according to the invention using a magnetic field sensor of the aforementioned type, the ring magnet surrounding the terminal part of the printed circuit board and the Hall element being arranged at least partially inside the ring magnet, and the terminal part of the printed circuit board comprising the ring magnet and the Hall element being arranged in an encapsulation housing made in the form of an injection-molded plastic part, the encapsulation housing fixing the ring magnet in a non-removable manner relative to the Hall element.

[0006] Thanks to the invention, it is advantageously possible, particularly in the case of high-volume production, which occurs regularly, for example, in the construction of motor vehicles, to manufacture the magnetic field sensor very precisely and with very high process reliability due to the special arrangement according to the invention of the printed circuit board end portion, the Hall effect sensor, the ring magnet, and the encapsulation housing. It is important in this case that the Hall effect sensor be arranged together with the ring magnet and the printed circuit board end portion inside the encapsulation housing.This ensures a permanently reliable connection between the Hall effect sensor and the ring magnet, guaranteeing exceptionally high measurement accuracy even during extended use of the magnetic field sensor. The encapsulation housing, an injection-molded plastic part, is made of a plastic material, preferably a thermosetting material.

[0007] According to the invention, it is particularly advantageous, for example, that a special clamping piece, which would otherwise have to be attached during the manufacturing of the magnetic field sensor in an additional bonding process step, is not required and can be saved. Advantageously, again according to the invention, for example, no additional positioning sleeve for the ring magnet is necessary. Furthermore, the invention advantageously allows for the manufacture of magnetic field sensors of different lengths without requiring a different tool for manufacturing these sensors.

[0008] The printed circuit board is preferably an elongated printed circuit board, that is, a printed circuit board with a longitudinal extension. The magnetic field sensor is, in particular, a bar-shaped magnetic field sensor. A longitudinal axis of the magnetic field sensor and a longitudinal axis of the printed circuit board preferably coincide.

[0009] The Hall element can, for example, be a surface-mountable component. Consequently, simultaneous mounting and soldering of the Hall element along with other electronic components on the printed circuit board is possible. The Hall element can, for example, be a Hall effect integrated circuit. In a particular embodiment, the Hall element can also be a Hall effect integrated circuit. The ring magnet can preferably be a permanent magnet. In a particular embodiment, the ring magnet can also be a permanent magnet.

[0010] The magnetic field sensor preferably has a sensor housing in which is arranged a sensor structural unit having the part The sensor assembly consists of a printed circuit board terminal, a Hall effect sensor, a ring magnet, and an encapsulation housing. The sensor housing is typically cylindrical. Preferably, the sensor housing is pot-shaped, especially in the area of ​​the sensor head. Furthermore, the sensor assembly may include not only the printed circuit board terminal but also the printed circuit board itself.

[0011] The sensor housing preferably fully encloses the printed circuit board, i.e., along its entire length, so that the printed circuit board and, consequently, the components mounted on and within it, are particularly well protected within the magnetic field sensor. Preferably, the sensor housing is filled with a sealing compound, at least in the region of the sensor head. The sealing compound may, for example, be an encapsulation or an encapsulating compound.

[0012] Particularly advantageously, according to the invention, an extremely robust embodiment, especially of the sensor head, can be obtained. Furthermore, the use of a surface-mountable Hall effect sensor is made possible, so that the entire assembly of the printed circuit board components can be carried out in a single process step. Moreover, even with different sensor length variants of the magnetic field sensor, it is possible to use only one plastic injection molding tool for all length variants of the magnetic field sensor.

[0013] The plastic encapsulation housing, particularly when the plastic is a thermosetting material, can exhibit a high insulating effect, so that the magnetic field sensor can have high ESD resistance, i.e., high safety against electrostatic discharge (ESD). For example, tests have shown that a layer thickness of just 0.7 mm of the plastic material can withstand 15 kV.Since, in the magnetic field sensor according to the invention, the encapsulation housing provides the desired or required ESD resistance, and therefore ESD protection, for the magnetic field sensor, it is not absolutely necessary for the sealing compound to fill the sensor housing in the region of the sensor head without bubbles, i.e., in particular without air pockets, and consequently to surround the encapsulation housing comprising the printed circuit board terminal and the Hall effect sensor. In this context, it is also possible, in the magnetic field sensor according to the invention, to provide in the region of the sensor head an increased wall thickness (in the direction of the longitudinal axis of the sensor, i.e., within the interior of the magnetic field sensor) of the sensor housing, so that the mechanical stability of the sensor housing can be increased and consequently... that a less robust housing material can be used, for example, for the sensor housing, which is usually made of metal.

[0014] The magnetic field sensor according to the invention is particularly suitable for use as a speed detector for a speed recorder of a motor vehicle, especially a commercial vehicle, for example, a heavy goods vehicle. Such a speed recorder may also be called a tachograph. The magnetic field sensor is connected to the tachograph and serves to provide the tachograph with a motion signal, in particular a vehicle speed signal.

[0015] Further advantageous improvements of the invention are indicated below.

[0016] According to an advantageous improvement of the invention, the printed circuit board end piece, the Hall effect sensor, and the ring magnet are injection-molded into the encapsulation housing. In this way, due to the complete encapsulation of the Hall effect sensor, the ring magnet, and the printed circuit board end piece, in addition to a particularly reliable attachment, special protection is also obtained, particularly for the Hall effect sensor and the ring magnet. The printed circuit board end piece, including any electronic components mounted on it, the Hall effect sensor, and the ring magnet can be completely embedded in the encapsulation housing, i.e., the plastic material of the encapsulation housing, so that no free space, filled for example with air, is present inside the encapsulation housing.

[0017] According to another advantageous improvement of the invention, the printed circuit board is made of an epoxy material, the plastic body of the Hall element is made of an epoxy material, and the encapsulation housing is made of a thermosetting material. Advantageously, the printed circuit board, the plastic body of the Hall element, and the encapsulation housing can thus be given similar coefficients of thermal expansion. Possible damage, particularly during the manufacturing of the magnetic field sensor, can therefore be avoided.Advantageously, thanks to this improvement of the invention, good compensation of the thermal expansion coefficients of the printed circuit board, the Hall element, and the encapsulation housing is possible, so that the magnetic field sensor can exhibit good robustness against temperature variations, for example, during the manufacturing of the magnetic field sensor. The epoxy material can, for example, be an epoxy resin. The plastic body of the Hall element can, in particular, be a plastic body of a Hall element implemented as a Hall effect integrated circuit.

[0018] For the possibility of manufacturing the magnetic field sensor in a plastic injection mold suitable for manufacturing magnetic field sensors of different sensor lengths, it is advantageous that, according to another improvement of the invention, the printed circuit board has at least one through-hole for receiving a means for attaching a plastic injection mold. The through-hole is preferably oriented perpendicular to a surface of the printed circuit board and may, in particular, be a receiving bore for the attachment means. The attachment means is, for example, a receiving pin. Such a receiving pin may also be called a positioning pin.

[0019] According to another advantageous improvement of the invention, the printed circuit board has a lateral cavity at one end of the encapsulation housing, which end of the encapsulation housing is opposite one end of the printed circuit board. The lateral cavity is particularly arranged in the region where the printed circuit board exits the encapsulation housing. The cavity is arranged at an edge or lateral surface of the printed circuit board and is preferably shaped like an arc. Preferably, a corresponding cavity is located at the respective opposite edges or lateral surfaces of the printed circuit board.Advantageously, during the manufacture of the magnetic field sensor, clamping or crushing ribs, arranged in a plastic injection molding tool used to manufacture the magnetic field sensor, which serve to correctly position the printed circuit board in the tool and / or to seal between the printed circuit board and the plastic injection molding tool to prevent plastic material from escaping during overmolding of the end portion of the printed circuit board, can engage in the lateral cavities.

[0020] According to another advantageous improvement of the invention, the Hall element is a component that can, in particular, be surface-mounted on a printed circuit board and has a Hall effect integrated circuit. Preferably, the Hall element is a Hall effect integrated circuit, and therefore, in particular, a surface-mountable Hall effect integrated circuit. Preferably, the Hall element is a surface-mountable component, in particular a surface-mountable component on the terminal portion of a printed circuit board. A surface-mountable component is also called an SMD (surface-mount device). The Hall effect integrated circuit is an integrated circuit (IC).

[0021] According to another advantageous improvement of the invention, the encapsulation housing is substantially cylindrical, with the housing's surface having at least one flattening or recess arranged parallel to the printed circuit board. Thanks to the substantially cylindrical shape of the encapsulation housing, it can advantageously correspond to the outer contour of the ring magnet, thus obtaining a particularly compact encapsulation housing. The ring magnet is preferably a hollow cylinder. The flattening or recess in the housing's surface allows for the flow of sealing compound from the encapsulation housing into a sensor housing during the manufacturing of the magnetic field sensor.The flattening or hollowing of the envelope surface therefore forms an overflow channel for the sealing mass at the level of the encapsulation housing.

[0022] The second objective above is achieved according to the invention by a method of manufacturing a magnetic field sensor, in particular a magnetic field sensor as described above, a Hall element being mounted on a printed circuit board surface of an end portion of a printed circuit board in an SMD process; a ring magnet is threaded onto the end portion of the printed circuit board having the Hall element; the printed circuit board having the Hall element and the ring magnet is inserted into a plastic injection molding tool having an injection molding mold;and the printed circuit board end portion comprising the Hall element and the ring magnet is overmolded with a plastic material in the injection mold, such that the plastic material forms an encapsulating housing surrounding the printed circuit board end portion comprising the Hall element and the ring magnet and permanently fixing the ring magnet relative to the Hall element. The indicated process steps are preferably carried out sequentially and in the order indicated.

[0023] Mounting the Hall element in an SMD process means that the Hall element is a surface-mountable component and is mounted in a process, namely the SMD process, suitable for mounting such a component on the printed circuit board. Preferably, the printed circuit board is fully equipped—that is, not only the end portion of the printed circuit board but also all other areas of the printed circuit board to be equipped—with the components intended for mounting, and is then inserted into the plastic injection molding tool, and the end portion of the printed circuit board is overmolded with the plastic material. Thus, complete assembly of the printed circuit board can be carried out in a single process step.

[0024] Thanks to the process according to the invention, a magnetic field sensor can be manufactured with particular reliability, even in large quantities. This magnetic field sensor has an encapsulation housing that permanently fixes a ring magnet relative to a Hall element. The plastic material forming the encapsulation housing surrounds the printed circuit board end portion comprising the Hall element and the ring magnet. After consolidation, in particular hardening, of the plastic material, the encapsulation housing fixes the ring magnet relative to the Hall element.

[0025] Advantageously, the printed circuit board is not completely overmolded, but only partially overmolded, namely only in the region of the end portion of the printed circuit board on the sensor head side. This partial overmolding forms the encapsulation housing. Due to this partial overmolding, the manufacturing process can be simplified and the plastic material used for overmolding can be saved. The injection mold of the plastic injection molding tool predefines the external shape of the encapsulation housing.

[0026] According to an advantageous improvement of the invention, a sealing pad that provides a seal between the injection mold and the printed circuit board is inserted into the plastic injection molding tool. Consequently, tolerances in the dimensions of the printed circuit board, particularly in its height (also called its thickness), can be reliably compensated for. The sealing pad can, for example, be a silicone pad. Two sealing pads can be provided, arranged on opposite sides of the printed circuit board between the plastic injection molding tool and the respective printed circuit board surface.Using the sealing pad(s), a seal can be achieved between the printed circuit board and the plastic injection molding tool to prevent plastic material from passing through during the overmolding of the end portion of the printed circuit board.

[0027] According to another advantageous improvement of the invention, the printed circuit board is optically detected before being inserted into the plastic injection molding tool. Optical detection of the printed circuit board may, for example, be a scan of the printed circuit board using a scanning device. Preferably, optical detection of the printed circuit board may be provided such that a production installation including the plastic injection molding tool receives information relating to the size, in particular the length, of The printed circuit board and therefore also related to the size, in particular the length, of the magnetic field sensor to be manufactured using the printed circuit board. Because of this information, the production facility knows, for example, which insertion position of the printed circuit board in the plastic injection mold must be used, and the receiving pins, necessary for securing the printed circuit board to the plastic injection mold, can be extended and the unnecessary receiving pins retracted.

[0028] According to another advantageous improvement of the invention, the ring magnet is supported, particularly laterally, in the plastic injection mold by means of a V-shaped support element. The V-shaped support element can, for example, be a V-shaped prism. The lateral support of the ring magnet can also be called a lateral support. Due to the V-shaped design of the support element, precise orientation of the ring magnet relative to the Hall element is simplified. Precise orientation of the ring magnet is necessary to prevent the ring magnet from tilting relative to the Hall element during the manufacturing of the magnetic field sensor and thus to ensure high measurement quality of the magnetic field sensor.A spring-loaded pin can also be incorporated into the plastic injection mold to press the ring magnet into the V-shaped support element, thereby preventing misalignment of the ring magnet. Overall, the V-shaped support element, and possibly the spring-loaded pin, facilitate the insertion and orientation of the ring magnet within the injection mold.

[0029] According to another advantageous improvement of the invention, the ring magnet is supported in the plastic injection molding tool by means of a forked contour at a front annular surface and at a rear annular surface in the longitudinal direction of the ring magnet. The front annular surface of the ring magnet is the annular surface facing one end of the printed circuit board, and the rear annular surface of the ring magnet is the annular surface of the ring magnet that is opposite the end of the printed circuit board in an assembled state of the magnetic field sensor.Support in the longitudinal direction of the ring magnet means support along the longitudinal axis of the printed circuit board and therefore also along the longitudinal axis of the magnetic field sensor. Support using a fork-shaped contour can advantageously ensure a distance, necessary for reliable operation of the sensor. magnetic field, of the front annular surface, i.e. the front front side, of the annular magnet to the Hall element can be maintained precisely.

[0030] According to another advantageous improvement of the invention, the ring magnet is supported vertically within the plastic injection molding tool by means of a pin in the plastic injection molding tool. The pin providing vertical support for the ring magnet can preferably be a spring pin, and in particular, it is a pin arranged within the plastic injection molding tool. Vertical support for the ring magnet means that it is a vertical support, as opposed to lateral support or support in the longitudinal direction. Preferably, the pin providing vertical support for the ring magnet presses the ring magnet against a bearing surface, particularly when the plastic injection molding tool is closed. The bearing surface is, in particular, a bearing surface of the plastic injection molding tool.In this way, production tolerances of the printed circuit board and / or the ring magnet can be compensated for, and when closing the plastic injection molding tool, damage to the ring magnet, especially if made from a fragile material, can be avoided.

[0031] According to another advantageous improvement of the invention, a sensor structural unit comprising the printed circuit board end portion, the Hall effect sensor, the ring magnet, and the encapsulation housing is inserted into a sensor housing. The sensor structural unit may, in particular, comprise the entire printed circuit board and not just the printed circuit board end portion. A sealing compound may preferably be introduced into the sensor housing either before or after the sensor structural unit is inserted into the sensor housing. If the sealing compound is introduced into the sensor housing before the sensor structural unit is inserted, the sensor structural unit must be inserted before the sealing compound consolidates, for example, by cross-linking.

[0032] According to another advantageous improvement of the invention, the sensor housing is closed at a second end opposite the first end of the sensor housing which has the Hall element. This results in particularly high protection of the components arranged in the sensor housing, especially components arranged on and at the printed circuit board, such as the Hall element and the ring magnet, and thus makes it difficult to tamper with the magnetic field sensor. The sensor housing can be closed, for example, using a plug-in socket which simultaneously allows a connection to an electrical connection line to a tachograph. The first end of the sensor housing is specifically part of a sensor head.

[0033] The invention also includes combinations of individual features of the embodiments described. The invention also relates to variants of the method according to the invention for manufacturing a magnetic field sensor that have characteristics as described above in relation to the variants of the magnetic field sensor according to the invention and vice versa.

[0034] Examples of embodiments of the invention are described in more detail below with the help of the schematic representations and sketches in the drawing.

[0035] In the figures:

[0036] [Fig-1] [Fig.1] illustrates a magnetic field sensor in a side view in perspective,

[0037] [Fig.2] [Fig.2] illustrates an exploded view of a magnetic field sensor assembly,

[0038] [Fig.3] [Fig.3] illustrates the entire [Fig.2] in an assembled state in a side view,

[0039] [Fig.4] [Fig.4] illustrates a first cross-sectional view of the assembly according to [Fig.3],

[0040] [Fig.5] [Fig.5] illustrates a second cross-sectional view of the assembly according to [Fig.3],

[0041] [Fig.6] [Fig.6] illustrates another cross-sectional view of the assembly according to [Fig.3],

[0042] [Fig.7] [Fig.7] illustrates an enlarged view of a cross-section of the assembly along the [Fig.3],

[0043] [Fig.8] ; [Fig.9] ; [Fig. 10] ; [Fig.11] Figures 8 to 11 illustrate the assembly according to Figures 3 and 7 in different states of production,

[0044] [Fig. 12] [Fig. 12] illustrates three assemblies comprising printed circuit boards of different lengths for magnetic field sensors of different sensor lengths and

[0045] [Fig. 13] [Fig. 13] illustrates the assemblies comprising printed circuit boards according to [Fig. 12] in a different representation.

[0046] Corresponding elements are respectively given the same reference symbols in all figures.

[0047] Fig. 1 illustrates in a perspective side view a magnetic field sensor 1 having a sensor head 2 at a first end of a sensor housing 4 and having a plug-in base 6 at a second end of a sensor housing 8, opposite the first end of the sensor housing 4, of a sensor housing 5 of the magnetic field sensor 1. The magnetic field sensor 1 is made in the shape of a bar and has a longitudinal sensor axis S.

[0048] Figure 2 illustrates in an exploded view an assembly 10 which is arranged inside a magnetic field sensor, for example a field sensor magnetic 1 as illustrated in [Fig. 1]. The assembly 10, which can also be called the sensor structural unit, comprises a printed circuit board 12, an encapsulation housing 14, and a ring magnet 16. In addition, a Hall element 22, for example a Hall effect integrated circuit, is arranged in the assembly 10 on a printed circuit board surface 20 of a printed circuit board terminal portion 18 of the printed circuit board 12.

[0049] The printed circuit board 12 is an elongated printed circuit board, having a longitudinal extent, having a longitudinal printed circuit board axis L. The printed circuit board end portion 18 of the printed circuit board 12 forms part of the sensor head 2 together with the encapsulation housing 14 and the ring magnet 16 as well as the Hall element 22 in an assembled state of the magnetic field sensor 1. The corresponding portion of the sensor housing 5 at the first end of the sensor housing 4 (see [Fig. 1]) also belongs to the sensor head 2. This portion of the sensor housing 5, which forms part of the sensor head 2, has an external thread 7 for fixing the magnetic field sensor 1, for example, in a transmission housing in a drivetrain of a motor vehicle.

[0050] For greater clarity, the assembly 10 shown in an exploded view in [Fig. 2] is shown in [Fig. 3] in a side view in an assembled state. [Fig. 4], which shows a first cross-sectional view of the assembly 10 along [Fig. 3] in a section along line DD, and [Fig. 5], which shows a second cross-sectional view of the assembly 10 along [Fig. 3] in a section through the encapsulation housing 14 and perpendicular to the longitudinal axis of the printed circuit board L (see [Fig. 2]), show that the ring magnet 16 surrounds the end portion of the printed circuit board 18 and the Hall element 22 is arranged at least partially inside the ring magnet 16.

[0051] By means of a pin not shown here, in particular a spring-loaded one, for example a downward retaining element, the ring magnet 16 can be supported vertically in a plastic injection molding tool during the manufacture of the magnetic field sensor 1. The pin can act on an upper surface FL. Opposite, on the ring magnet 16, there is, by way of example, a lower rigid bearing surface F2.

[0052] Lateral support surfaces F3, F4 on the ring magnet 16 can serve as V-shaped lateral support for the ring magnet 16 during the manufacture of the magnetic field sensor 1. In this case, the ring magnet 16 can be supported in the plastic injection molding tool by means of a V-shaped support element. Furthermore, the ring magnet 16 can be supported during the manufacture of the magnetic field sensor 1 in the plastic injection molding tool. plastic using a fork-shaped contour at the level of a front annular surface FV and at the level of a rear annular surface FH (cf. [Fig.4]) in the longitudinal direction of the annular magnet 16.

[0053] The terminal part of the printed circuit board 18 comprising the ring magnet 16 and the Hall element 22 is arranged in the encapsulation housing 14 which is made in the form of an injection molded part in plastic material. Figure 6 illustrates another side view of the assembly 10 according to Figure 3, which shows that the encapsulation housing 14 is completely closed at the level of a front side 24 (see Figure 4) of the assembly 10. The encapsulation housing 14, which permanently fixes the ring magnet 16 relative to the Hall element 22, is formed by an overmolding of the printed circuit board end portion 18, as well as the Hall element 22 arranged on the printed circuit board end portion 18 and the ring magnet 16 also arranged on the printed circuit board end portion 18.

[0054] The encapsulation housing 14 is substantially cylindrical (see [Fig. 2]). In the embodiment illustrated here, one surface of the encapsulation housing 14 has three flattened areas 21, 23, 27 arranged parallel to the printed circuit board 12, as well as a recess 25 arranged parallel to the printed circuit board 12. The flattened areas 21, 23, 27 and the recess 25 form overflow channels for a sealing compound during the manufacture of the magnetic field sensor 1.

[0055] The printed circuit board end portion 18, the Hall element 22 and the ring magnet 16 are injection-molded into the encapsulation housing 14. This means that the representation according to [Fig.2] is only an illustration of the essential components of the assembly 10, namely the printed circuit board 12 comprising the Hall element 22, the ring magnet 16 and the encapsulation housing 14, and does not illustrate individual elements before their assembly, since the encapsulation housing 14 is formed in an injection molding operation only after assembly of the Hall element 22, the printed circuit board 12 and the ring magnet 16.

[0056] The printed circuit board 12 has a through-hole 26, which may, for example, be a receiving bore, used to receive a means for attaching a plastic injection molding tool during the manufacture of the magnetic field sensor 1. Furthermore, the printed circuit board 12 has two lateral cavities 32, 33 at one end of the encapsulation housing 28 of the encapsulation housing 14, which end of the encapsulation housing 28 is opposite one end of the printed circuit board 30 of the printed circuit board terminal portion 18. The cavities 32, 33 are arranged respectively opposite each other at a printed circuit board edge, more precisely at a the lateral surface of the printed circuit board 12 and are made in the shape of an arc of a circle.

[0057] During the manufacture of the magnetic field sensor 1, clamping or crushing ribs, optionally arranged in the plastic injection molding tool, serving to correctly position the printed circuit board 12 in the plastic injection molding tool and / or, acting then as sealing ribs, serving to seal between the printed circuit board 12 and the plastic injection molding tool to prevent plastic material from escaping during overmolding of the printed circuit board end portion 18, overmolding during which the encapsulation housing 14 is produced, may engage in the lateral cavities 32, 33. Preferably, the through recess 26 and the cavities 32, 33 may be drilled in a clamping device during the manufacture of the magnetic field sensor 1.

[0058] Fig. 7 illustrates an enlarged view of a cross-section of assembly 10 according to Fig. 3, The encapsulation housing 14 is represented by dotted lines to illustrate the position and arrangement of the encapsulation housing 14 with respect to the components located inside the encapsulation housing 14, namely the ring magnet 16, the Hall element 22 and the printed circuit board terminal portion 18. The Hall element 22 is a surface-mountable component on the printed circuit board 12 and features a Hall effect integrated circuit.

[0059] A method for manufacturing a magnetic field sensor 1 is described below with reference to Figures 8 to 11. During manufacturing, a Hall effect element 22, in particular a Hall effect element 22 made in the form of a Hall effect integrated circuit, is first mounted on a printed circuit board surface 20 of a printed circuit board end portion 18 of a printed circuit board 12 in a surface-mount technology (SMT) process (see [Fig. 8]). Then, a ring magnet 16 is threaded onto the printed circuit board end portion 18 bearing the Hall effect element 22 (see [Fig. 9]). The ring magnet 16 can be freely cantilevered, and positioning of the ring magnet 16 in a plastic injection molding tool is possible.

[0060] Then the printed circuit board 12 comprising the Hall element 22 and the ring magnet 16 is inserted into a plastic injection molding tool, not shown here, having an injection mold. Next, the end portion of the printed circuit board 18 comprising the Hall element 22 and the ring magnet 16 is overmolded with a plastic material in the injection mold, so that the plastic material forms, after consolidation, in particular hardening, an encapsulation housing 14 surrounding the end portion of the printed circuit board 18 comprising the element of Hall 22 and the ring magnet 16 and fixing the ring magnet 16 in a non-removable manner with respect to the Hall element 22 (cf. [Fig. 10]).

[0061] Overall, using the encapsulation housing 14, the components, namely the printed circuit board end portion 18, the Hall element 22, and the ring magnet 16, are fixed relative to each other. To illustrate in particular the components arranged inside the encapsulation housing 14, the arrangement of [Fig. 10] is shown in [Fig. 11] by an encapsulation housing 14 represented by dashed lines, the components, namely the Hall element 22, the ring magnet 16, and the printed circuit board end portion 18, which are arranged inside the encapsulation housing 14, also being visible.

[0062] Figure 12 illustrates side by side three different assemblies 10, 10', 10" comprising printed circuit boards 12, 12', 12" of different lengths for magnetic field sensors of different sensor lengths. In this case, the assembly 10 shown on the left in Figure 12 corresponds to the assembly shown in Figure 3. The assembly 10' shown in the center and the assembly 10" shown on the right differ from the first assembly 10 only in terms of the differences in lengths of the respective printed circuit boards 12, 12', 12". In all the length variants shown, the respective encapsulation housing 14, 14', 14" is at the same height, which shows that it corresponds to the arrangement during the manufacture of the respective magnetic field sensor, regardless of its sensor length, in a single plastic injection mold.

[0063] In order to be able to manufacture magnetic field sensors of different sensor lengths in a single plastic injection molding tool, the printed circuit boards 12, 12', 12" respectively have, in a first variant A, at a corresponding location in a printed circuit board region which is arranged near a respective printed circuit board terminal part 18, a forward through recess 34, 34', 34" in particular a receiving bore, serving to receive a receiving pin of the plastic injection molding tool. The respective position of the through-hole 34, 34', 34" in the printed circuit boards 12, 12', 12" is in this case coincident, that is to say that the position of the through-holes 34, 34', 34" relative to the plastic injection molding tool is the same.

[0064] In a second alternative variant B, which is also shown in the representation illustrated in [Fig. 12] for clarity and for comparison, corresponding lateral through recesses 26, 26', 26" in particular receiving bores are arranged in different positions in the printed circuit boards 12, 12', 12".

[0065] Figure 13 illustrates the assemblies 10, 10', 10" comprising printed circuit boards 12, 12', 12" according to Figure 12 in a different representation. In this representation, in which the printed circuit boards 12, 12', 12" are shown superimposed, corresponding to a respective position of the respective printed circuit board 12, 12', 12" in the plastic injection mold, the difference with respect to the plastic injection mold not shown here is particularly evident. In the first variant A, the through-hole 34, 34', 34" in front of the respective printed circuit board 12, 12', 12" is arranged in the same position with respect to the plastic injection mold not shown here.In all length variants, the respective through recess 34, 34', 34" in particular the receiving bore, in the first variant A has the same distance to a hollow of the plastic injection molding tool, so that only a corresponding receiving pin, arranged here centrally, of the plastic injection molding tool is required.

[0066] In contrast, in the second variant B, the respective lateral through-hole 26, 26', 26" of the respective printed circuit board 12, 12', 12" is arranged in a different position relative to the plastic injection molding tool, so that the latter must, in the second variant B, have different receiving pins, each associated with a specific length of printed circuit board. During the manufacture of the respective magnetic field sensor, the receiving pins must penetrate the plastic injection molding tool according to the length variant; only the required receiving pin(s) may protrude.

Claims

Demands

1. A magnetic field sensor (1) comprising a sensor head (2), the sensor head (2) having a printed circuit board end portion (18) of a printed circuit board (12) and a Hall element (22) and a ring magnet (16) on the printed circuit board end portion (18), characterized in that the ring magnet (16) surrounds the printed circuit board end portion (18) and the Hall element (22) is arranged at least partially inside the ring magnet (16), and in that the printed circuit board end portion (18) comprising the ring magnet (16) and the Hall element (22) is arranged in an encapsulation housing (14) made as an injection-molded plastic part, the encapsulation housing (14) permanently fixing the ring magnet (16) in relation to Hall's element (22).

2. Magnetic field sensor (1) according to claim 1, characterized in that the printed circuit board terminal part (18), the Hall element (22) and the ring magnet (16) are injection-encapsulated in the encapsulation housing (14).

3. Magnetic field sensor (1) according to claim 1 or 2, characterized in that the printed circuit board (12) has an epoxy material, a plastic body of the Hall element (22) has an epoxy material and the encapsulation housing (14) has a thermosetting material.

4. Magnetic field sensor (1) according to any one of the preceding claims, characterized in that the printed circuit board (12) has at least one through recess (26; 34) for receiving a means for attaching a plastic injection molding tool.

5. Magnetic field sensor (1) according to any one of the preceding claims, characterized in that the printed circuit board (12) has a lateral cavity (32) at one end of the encapsulation housing (28) of the encapsulation housing (14), which end of the encapsulation housing (28) is opposite one end of the printed circuit board (30) of the printed circuit board terminal portion (18).

6. Magnetic field sensor (1) according to any one of the preceding claims, characterized in that the Hall element (22) is an SMD type component and has a Hall effect integrated circuit.

7. Magnetic field sensor (1) according to any one of the preceding claims, characterized in that the encapsulation housing (14) is made in a substantially cylindrical manner, an envelope surface of the encapsulation housing (14) having at least one flattening (21) or recess (25) arranged parallel to the printed circuit board (12).

8. A method for manufacturing a magnetic field sensor (1), in particular a magnetic field sensor according to any one of the preceding claims, characterized in that - a Hall element (22) is mounted on a printed circuit board surface (20) of an end portion (18) of a printed circuit board (12) in an SMD process, - a ring magnet (16) is threaded onto the end portion of the printed circuit board (18) having the Hall element (22), - the printed circuit board (12) having the Hall element (22) and the ring magnet (16) is inserted into a plastic injection molding tool having an injection mold, - the end portion of the printed circuit board (18) having the Hall element (22) and the ring magnet (16) is overmolded with a plastic material in the injection mold,so that the plastic material forms an encapsulation housing (14) surrounding the terminal portion of the printed circuit board (18) comprising the Hall element (22) and the ring magnet (16), and permanently fixing the ring magnet (16) relative to the Hall element (22).

9. Method according to claim 8, characterized in that a sealing cushion achieving the sealing of the injection mold with respect to the printed circuit board (12) is inserted into the plastic injection molding tool.

10. A method according to any one of claims 8 or 9, characterized in that the printed circuit board (12) is optically detected before the printed circuit board (12) is inserted into the plastic injection molding tool.

11. A method according to any one of claims 8 to 10, characterized in that the ring magnet (16) is supported in the plastic injection molding tool by means of a V-shaped support element.

12. A method according to any one of claims 8 to 11, characterized in that the ring magnet (16) is supported in the plastic injection molding tool by means of a fork-shaped contour at the level of a front ring surface (FV) and at the level of a rear ring surface (FH) in the longitudinal direction of the ring magnet (16).

13. A method according to any one of claims 8 to 12, characterized in that the ring magnet (16) is supported vertically in the plastic injection molding tool by means of a pin of the plastic injection molding tool.

14. A method according to any one of claims 8 to 13, characterized in that a sensor structural unit having the printed circuit board terminal part (18), the Hall element (22), the ring magnet (16) and the encapsulation housing (14) is inserted into a sensor housing (5).

15. Method according to claim 14, characterized in that the sensor housing (5) is closed at a second sensor housing end (8) opposite the first sensor housing end (4) having the Hall element (22).

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