Sensor, main body of a sensor and method for producing a sensor

Abstract

With regard to safe and fast production of a sensor using means of simple design, a sensor, in particular an inductive sensor, for detecting the distance to a measurement object, having a main body (1) for arranging a sensor element (2) on the main body (1), is designed and developed in such a way that the main body (1) has at least one positioning element (3, 4) for predefined radial or concentric and for predefined axial positioning of the main body (1) in a housing or installation space. A main body (1) of a sensor and a corresponding method for producing such a sensor are also specified.

Description

[0001] SENSOR, BASIC BODY OF A SENSOR AND METHOD FOR MANUFACTURING A SENSOR

[0002] The invention relates to a sensor, in particular an inductive sensor for detecting the distance to a measuring object, with a base body for arranging a sensor element on the base body.

[0003] Furthermore, the invention relates to a base body of a sensor.

[0004] Furthermore, the present invention relates to a method for manufacturing a sensor, wherein the sensor comprises a base body, a sensor element arranged on the base body and a partial encapsulation or overmolding of the base body, comprising the following steps:

[0005] Providing the basic body;

[0006] Arranging the sensor element on the base body; and section by section encasing or overmolding the base body.

[0007] Sensors of the type mentioned above, as well as corresponding manufacturing processes, are known from practice and exist in different embodiments.

[0008] For example, inductive sensors based on current-carrying coils are known, and these inductive sensors can be used as non-contact distance sensors. Such sensors are considered particularly robust and extremely precise and are therefore often used in industrial environments where high accuracy is required. These sensors are especially suitable for use under pressure and high temperatures, and in environments where they are exposed to oil and dirt.

[0009] The basic structure of inductive sensors is based on a wound coil, usually a copper coil, as the sensing element. The coil is wound onto a base, which can be called a coil former, that holds or supports the coil. The coil former also extends the ends of a coil wire to a point where contact can be made with a sensor cable or connector. The wound coil former is then inserted into or overmolded in a housing, for example, made of aluminum, stainless steel, or plastic. In addition to other mechanical fixing methods and adhesives, a potting compound can be used to secure the coil former within the housing. After the potting compound has cured, the coil former and housing form a solid unit.

[0010] These types of sensors are considered extremely precise and are also used for measurements with sub-micrometer accuracy. This high accuracy requires high precision in the manufacturing process. It is crucial that the coil former is always correctly positioned within the housing. This position must remain unchanged throughout the sensor's lifespan. Any improper installation, resulting in a change in the coil or sensor element's position within the housing, will lead to inaccurate measurements.

[0011] Besides encapsulating a coil former in a housing, other manufacturing processes are known. For example, DE 10 2018 132 709 A1, entitled “Inductive speed sensor and a method for its manufacture”, describes a multi-part injection molding process. In this process, a wound base body or coil former 100 is subsequently overmolded or encased with a plastic material using a further injection molding process to form a sheath 200. The coil former has several fixing elements. These fixing elements can include additional anti-rotation devices 150, which prevent the coil former 100 from rotating relative to the mold during the formation of the sheath 200. Consequently, the anti-rotation devices 150 ensure correct positioning within and relative to the mold.

[0012] The anti-rotation features 150 project at least partially from the outer casing 200 or extend at least to a surface of the outer casing 200 and can become part of a rib 230 or a plateau 240, with both the rib 230 and the plateau 240 being subsequently formed as part of the outer casing 200 during the overmolding process. These ribs 230 and plateaus 240 serve to fix a sleeve or housing to the outer casing 200, for example by crimping.

[0013] As explained above, a multi-stage injection molding process for manufacturing sensors of the type mentioned above, such as inductive sensors, is state of the art, particularly for lower price segments. However, during the production of such a sensor, for example, through two injection molding steps to produce the base body and the subsequent overmolding, there is a risk that the outer geometry or the casing will be incorrectly executed during the subsequent overmolding. The above-mentioned patent application describes the correct positioning of the base body or coil former in the injection mold using an anti-rotation device 150. However, errors in the formation of the casing itself, such as tolerances arising therein, are not taken into account.This means that, with the known manufacturing process, the exact position of the coil former or coil within the casing or within a housing containing the coil former cannot be determined after the second injection molding process. This is because, for example, tolerances introduced during the forming of the casing lead to tolerances in the positioning of the coil former or coil within the housing. Therefore, considering high precision requirements and the need to reliably achieve correspondingly high-quality measurement results, calibration of the sensors after their manufacture is necessary, which takes time and thus incurs costs.

[0014] The present invention is therefore based on the objective of providing a sensor, a sensor body and a method for manufacturing such a sensor, whereby a safe and fast manufacture of a sensor is made possible with structurally simple means.

[0015] According to the invention, the foregoing problem is solved by a sensor having the features of claim 1, a base body according to claim 12 and by a method for manufacturing a sensor having the features of claim 13.

[0016] According to claim 1, the sensor is designed and further developed such that the base body has at least one positioning element for a predetermined radial or concentric and for a predetermined axial positioning of the base body in a housing or installation space.

[0017] Furthermore, according to claim 13, the method for manufacturing a sensor is designed and further developed such that the base body has at least one positioning element not covered by the casing or overmolding for a predetermined radial or concentric and for a predetermined axial positioning of the base body in a housing or installation space.

[0018] In accordance with the invention, it has first been recognized that the aforementioned problem is solved in a surprisingly simple manner through a clever design of the base body. In a further aspect of the invention, the base body has at least one positioning element for a predetermined radial or concentric and for a predetermined axial positioning of the base body in a housing or installation space. With one or more such positioning elements, it is possible to define the final positioning of the base body in a housing or installation space at the end of the sensor manufacturing process. This is achieved independently of any further manufacturing steps, such as encasing or overmolding the base body before its placement in a housing or installation space.It is only necessary to ensure that the at least one positioning element remains uncovered by any coating or overmolding, so that direct contact between the at least one positioning element and a housing is guaranteed in the finished state of the sensor. It is essential that the base body according to the invention ensures not only radial or concentric positioning of the base body, but also axial positioning of the base body within a housing or installation space. Tolerances introduced during overmolding or coating are no longer relevant, since the position of the base body within the housing or installation space is predetermined by the at least one positioning element. Therefore, calibration of the sensors after their manufacture is no longer necessary, thus saving time and costs during production.

[0019] The prior art makes no mention of such a predetermined radial, concentric, or axial positioning. It focuses solely on the secure fixing of a housing.

[0020] The method according to the invention is specifically implemented such that the base body retains at least one positioning element, not covered by the casing or overmolding, for a predetermined radial or concentric and for a predetermined axial positioning of the base body in a housing or installation space during manufacturing. The casing or overmolding thus does not conceal or cover the at least one positioning element, so that in the manufactured state of the sensor, there is direct contact between the at least one positioning element and a housing or installation space. The result is a precisely predetermined positioning of the base body in a housing or installation space.

[0021] Consequently, the sensor, the base body and the method according to the invention provide a sensor, a base body and a method according to which a safe and fast manufacture of a sensor is made possible with structurally simple means.

[0022] In a specific embodiment, the base body can be partially encased or overmolded. Such an encasement or overmolding, which can cover at least part of a sensor element, does not, however, conceal the at least one positioning element.

[0023] In another specific embodiment, the sensor can have a housing such that at least part of the encased or overmolded base body and / or at least part of a sensor element can be arranged in the housing or in another installation space. In a structurally simple design, the housing can have a substantially cylindrical cross-section or be cylindrical in shape. However, other housing shapes are also possible. The housing can be adapted to the shape of the base body, enabling a particularly precise arrangement of the base body within the housing.

[0024] The base body and / or the housing can, in principle, take on a variety of different shapes, which can be tailored to a specific application. The base body and / or the housing can have a longitudinal axis for radial or concentric and axial positioning, so that the specified radial or concentric and axial positioning is defined relative to this longitudinal axis.

[0025] The at least one positioning element can be designed as a single element that provides both the specified radial or concentric and axial positioning. Alternatively, at least one positioning element can be designed or implemented for radial or concentric positioning and at least one further positioning element for axial positioning. In this latter case, different positioning elements are provided for radial or concentric positioning and for axial positioning, whereby multiple positioning elements for radial or concentric positioning and multiple positioning elements for axial positioning can be implemented.

[0026] With a view to ensuring particularly secure positioning of the base body in a housing or installation space, the at least one positioning element can be designed as a radial or axial positioning surface. This allows for a particularly stable and secure planar contact between the positioning element and the housing or installation space, so that a predetermined positioning can be reliably maintained even over long periods of sensor operation. In exemplary embodiments of the sensor or base body according to the invention, the at least one positioning surface can serve as or be designated as a reference surface. In a specific and simple embodiment, the base body can be manufactured as a one-piece casting, in particular as an injection-molded part.

[0027] Furthermore, with a view to a simple and cost-effective embodiment, the base body and / or the casing or overmolding can be made of plastic, preferably of a thermoset or a thermoplastic.

[0028] In principle, the sensor can be based on different operating principles. Specifically, the sensor can be designed as an inductive or capacitive sensor.

[0029] In a further specific embodiment, particularly in the realization of an inductive sensor, the base body can have or be a coil former, and / or the sensor element can have a coil. Such a coil can be wound onto the base body or coil former.

[0030] For easy and secure mounting of a sensor cable connected to a sensor element, the base body can have a passage for the sensor cable. When the sensor is mounted, the sensor cable can thus extend through the base body into the interior of the housing.

[0031] Fundamentally, for an accurate measurement with an embodiment of the sensor according to the invention, the correct positioning of the sensor element, for example a coil, is essential. With embodiments of the sensor according to the invention, it can be ensured that the base body or coil body is always reproducibly positioned in the predetermined position in the housing or installation space.

[0032] Exemplary embodiments of the sensor according to the invention show, for example, a base body or coil body made of plastic, preferably thermoset, located inside a housing or installation space, which has one or more positioning elements or one or more reference surfaces that guarantee that the base body or coil body, which is encased in a second process step, is correctly positioned during assembly in the housing or installation space.

[0033] There are now various ways to advantageously develop and further refine the teaching of the present invention. For this purpose, reference is made, on the one hand, to the dependent claims and, on the other hand, to the following explanation of preferred embodiments of the sensor, the base body, and the method according to the invention with reference to the drawing. In conjunction with the explanation of the preferred embodiments with reference to the drawing, generally preferred embodiments and further developments of the teaching are also explained. The drawing shows

[0034] Fig. 1 shows a perspective view of an embodiment of a base body of the sensor according to the invention.

[0035] Figs. 2-4 show the embodiment from Fig. 1 in various side views.

[0036] Fig. 5 shows a front view of the embodiment from Fig. 1 ,

[0037] Fig. 6 shows a further front view of the embodiment from Fig. 1 in an overmolded state,

[0038] Fig. 7 shows a cutaway view of the embodiment from Fig. 1 in the overmolded state with a sensor element in the form of a coil and

[0039] Fig. 8 shows a further perspective view of the embodiment from Fig. 1 in the overmolded state.

[0040] Fig. 1 shows a perspective view of an embodiment of a base body 1 of a sensor according to the invention. The base body 1 is suitable for an inductive sensor for detecting the distance to a measuring object. A sensor element 2 in the form of a coil, shown in Fig. 7, can be arranged in the front region of the base body 1. For particularly precise and reliable positioning of the base body 1 in a housing or installation space, the base body 1 has several positioning elements 3 for a predetermined radial or concentric positioning of the base body 1 and several positioning elements 4 for a predetermined axial positioning of the base body 1 in a housing or installation space.

[0041] In the manufacture of the sensor, the base body 1 is typically provided with an overmolding 5 as shown in Figures 6 to 8. This overmolding 5 is arranged section by section on the base body 1.

[0042] The base body 1 has a longitudinal axis 6, shown particularly in Figures 2 to 4, which each depict a side view of the base body 1. The radial or concentric and axial positioning is referenced to this axis. The positioning elements 3 each have a radial positioning surface 7, which, when mounted in a housing or installation space, comes into direct contact with the housing or installation space. Furthermore, the positioning elements 4 each have an axial positioning surface 8 for direct contact with the housing or installation space. This means that an overmolding 5 must be designed such that the positioning elements 3 and 4 with the positioning surfaces 7 and 8 are not covered by the overmolding 5 during the overmolding process, but remain free and uncovered to ensure direct contact with a housing or installation space. The base body 1 also has two contact pins 9.

[0043] The production of an exemplary embodiment of a sensor can essentially comprise four process steps. Already in the first process step, the production of the inner base body 1 or coil former, the positioning elements 3 and 4 with the positioning surfaces 7 and 8, which can also be referred to as reference surfaces, are manufactured for the correct positioning of the sensor in the housing or installation space at a measuring point. Such a base body 1 is shown in Fig. 1. The positioning surfaces 7 and 8, shown particularly in Fig. 1, are also present after the second injection molding process, the overmolding or coating to produce the overmolding 5, and thus ensure the correct concentric positioning in the housing or installation space of the sensor. For clarification, a front view of the base body 1 or coil former is shown in Fig. 5.Positioning elements 3 and 4 with positioning surfaces 7 and 8 in the form of positioning lugs can be seen, which center a sensor element 2 together with the base body 1 in the housing or installation space, for example a bore.

[0044] Fig. 6 shows a front view of an overmolded base body 1 or coil body of the inductive sensor. The positioning surfaces 7 and 8 or reference surfaces produced in the first injection molding process step, together with the overmolding 5 added in the second injection molding process step, now form the outer contour of the sensor containing the sensor element 2.

[0045] The positioning surfaces 7 or reference surfaces of the base body 1 or coil former described in Figures 5 and 6 ensure radially or concentrically correct positioning. Here, four radial positioning surfaces 7 are implemented at a distance of approximately 90° from each other. However, fewer or more than four positioning surfaces 7 can also be implemented, as long as reliable radial or concentric positioning is ensured. The radial positioning surfaces 7 prevent the inductive sensor from tilting in the housing or installation space and ensure radial or concentric centering.

[0046] Additionally, positioning in the axial direction is essential for a correct measurement task. For this purpose, the inner base body 1 or coil body has three further positioning surfaces 8 or reference surfaces, which are also shown in Figures 5 and 6.

[0047] The lower positioning element 3, 4 shown in Fig. 5 has a dual function in the form of a radial or concentric positioning element 3 with a positioning surface 7 and an axial positioning element 4 with a positioning surface 8. As such a positioning element 3, 4, which can also be described as a nose, it thus fulfills two tasks. The surface of the nose parallel to the plane of Fig. 5 forms the positioning surface 8 or reference surface for axial positioning, and the surface perpendicular to the plane of Fig. 5 forms the positioning surface 7 or reference surface for radial concentric positioning. This dual function is particularly evident in Fig. 7, which shows a cutaway view of the embodiment from Fig. 1 in the overmolded state with a sensor element 2 in the form of a coil.The inner base body 1 or coil body is shown with triple hatching and the overmolding 5 or sheathing with single hatching.

[0048] The inner base body 1, or coil former, therefore has positioning surfaces 7, 8, or reference surfaces for axial and radial positioning, which are also present in the outer contour of the finished sensor after overmolding / encasing to form the overmolding 5, i.e., after the second injection molding process step. Consequently, the base body 1, or coil former, and thus the sensor, can be correctly positioned in a housing or installation space. Only the tolerances of the coil former are effective; the tolerances of the overmolding are not, since the crucial reference surfaces of the coil former are not overmolded.

[0049] Fig. 8 shows a further perspective view of the embodiment from Fig. 1 in the overmolded and thus finished state of the sensor. In this state, the sensor can be precisely arranged in a housing or installation space.

[0050] The base body 1 can have elements or lugs for correctly positioning it in an injection mold. These can be additional elements or lugs. However, positioning elements 3 and 4 can also be used for a dual function to ensure correct positioning in the injection mold. These elements, lugs, or positioning elements 3 and 4 can also act as an anti-rotation device.

[0051] The described manufacturing method allows for a reduction in the production costs of sensors, particularly inductive sensors, compared to previous methods. Furthermore, a lower reject rate and thus an increase in quality can be expected due to the particularly precise and accurate positioning of a base body 1 or coil former, especially an overmolded one, within a housing or installation space. A thermoset is preferably used as the material for the injection molding process. However, other plastics, such as thermoplastics, are also conceivable. Thermosets offer several advantages. For example, the injection pressure is lower than with thermoplastics. This allows for a simpler design of the injection mold, as lower forces are involved. In addition, no complex components such as hot runner nozzles are required.Additionally, the lower injection pressure reduces the risk of damaging the coil or connecting wires. Besides the process advantages, thermosets themselves offer further benefits. Compared to thermoplastics, thermosets exhibit high temperature resistance. They are also comparatively resistant to chemicals.

[0052] In summary, the invention offers, among other things, the following advantages: Reproducible and precise positioning of the base body 1, and thus of the sensor element 2 or the sensor coil of an inductive sensor, which is manufactured using a cost-effective process, within a housing or installation space. The positioning surface 7 or 8, or reference surface, is located directly on the housing or installation space, so that the inductive sensor does not require subsequent calibration after installation. This results in savings of time and costs.

[0053] In an embodiment of the sensor according to the invention, a sensor or inductive sensor, each for detecting the distance to a measuring object, can be designed and further developed such that it has an internal base body 1 or coil body, which is produced by a first injection molding process step, wherein the internal base body 1 or coil body has one or more positioning elements or one or more positioning surfaces or reference surfaces for radial, concentric positioning and one or more positioning elements or one or more positioning surfaces or reference surfaces for axial positioning, wherein the positioning elements or positioning surfaces or reference surfaces are also present after the second injection molding process step, the overmolding 5 or encapsulation.

[0054] Regarding further advantageous embodiments of the sensor according to the invention-

[0055] For details of the basic body according to the invention and the method according to the invention, reference is made to the general part of the description and to the attached claims to avoid repetition.

[0056] Finally, it should be expressly pointed out that the aforementioned exemplary embodiments serve only to discuss the claimed teaching, but do not limit it to these exemplary embodiments.

[0057] Reference symbol list

[0058] 1 Basic body

[0059] 2 Sensor element

[0060] 3 Positioning element (radial, concentric)

[0061] 4 Positioning element (axial)

[0062] 5. Overmolding

[0063] 6 Longitudinal axis

[0064] 7 radial positioning surface

[0065] 8 axial positioning surfaces

[0066] 9 contact pin

Claims

Claims 1. Sensor, in particular an inductive sensor for detecting the distance to a measuring object, with a base body (1) for arranging a sensor element (2) on the base body (1), characterized in that the base body (1) has at least one positioning element (3, 4) for a predetermined radial or concentric and for a predetermined axial positioning of the base body (1) in a housing or installation space.

2. Sensor according to claim 1, characterized in that a sheathing or overmolding (5) of the base body (1) is arranged section by section on the base body (1).

3. Sensor according to claim 2, characterized in that at least a part of the encased or overmolded base body (1) and / or at least a part of a sensor element (2) are arranged in a housing or installation space.

4. Sensor according to claim 3, characterized in that the housing has a substantially cylindrical cross-section or is cylindrical in shape.

5. Sensor according to one of claims 1 to 4, characterized in that the base body (1) and / or the housing has or has a longitudinal axis (6) for radial and axial positioning.

6. Sensor according to one of claims 1 to 5, characterized in that at least one positioning element (3) is provided for radial or concentric positioning and at least one further positioning element (4) is provided for axial positioning.

7. Sensor according to one of claims 1 to 6, characterized in that the at least one positioning element (3, 4) is designed as a radial (7) or axial positioning surface (8).

8. Sensor according to one of claims 1 to 7, characterized in that the base body (1 ) is manufactured as a one-piece casting, in particular as an injection molded part.

9. Sensor according to one of claims 1 to 8, characterized in that the base body (1 ) and / or the casing or overmolding (5) is made of plastic, preferably of a thermoset or a thermoplastic.

10. Sensor according to one of claims 1 to 9, characterized in that the sensor is designed as an inductive or capacitive sensor.

11. Sensor according to one of claims 1 to 10, characterized in that the base body (1) has a coil body or is a coil body and / or that the sensor element (2) has a coil.

12. Base body (1) of a sensor according to one of claims 1 to 11.

13. Method for manufacturing a sensor, in particular a sensor according to one of claims 1 to 11, wherein the sensor comprises a base body (1), a sensor element (2) arranged on the base body (1), and a partial sheathing or overmolding (5) of the base body (1), comprising the following steps: Providing the basic body (1 ); Arranging the sensor element (2) on the base body (1); and sectionally encasing or overmolding the base body (1); characterized in that the base body (1) has at least one positioning element (3, 4) not covered by the encasing or overmolding (5) for a predetermined radial or concentric and for a predetermined axial positioning of the base body (1) in a housing or installation space.

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