Sensor and method for installing a sensor unit in a sensor housing of such a sensor

Abstract

In a sensor having a tubular sensor housing (100) and having a sensor unit (200) which can be fastened in the interior of the sensor housing (100), the sensor unit (200) can be fastened axially immovably in the sensor housing (100) by means of a retaining ring (400) which can be positioned on a sensor package (210), when the sensor unit (200) is installed in the sensor housing (100), the retaining ring finally rests in a retaining ring receptacle produced between the sensor package (210) and the sensor housing (100).

Description

Technical Field

[0001] This invention relates to a sensor of the type described in claim 1. The subject of this invention is also a method for mounting a sensor unit within a sensor housing of such a sensor. Background Technology

[0002] Modern sensors, especially miniature sensors, have electronic circuitry for evaluating sensor signals, setting sensor parameters, and so on. The electronic circuitry and the actual sensor element are often housed in very small, typically cylindrical, enclosures. These enclosures often have external threads, allowing them to be mounted like screws into machine parts, housings, etc.

[0003] In the case of known sensors, the electronic circuitry and sensor elements are typically embedded in a sensor package made of, for example, thermosetting materials, and secured to the interior of a tubular housing by means of adhesives or suitable flanges. However, adhesives or fillers, such as resins, foams, etc., are generally hazardous, not very environmentally friendly, or even toxic materials. Furthermore, they are difficult to handle, especially when it comes to transportation, storage, filling, curing time / temperature, etc.

[0004] Another fastening option known from existing technology is flanging. However, this requires special tools, flanging punches, presses, etc. Furthermore, tubular sensor housings are easily damaged under this type of fastening method.

[0005] One type of sensor known from the prior art is found, for example, in DE 20 2013 007 756 U1.

[0006] The present invention solves the problem of overcoming the aforementioned disadvantages and provides a sensor that is easy and quick to install, resistant to external influences, and in particular waterproof. Summary of the Invention

[0007] The sensor according to the invention has the advantages of easy and quick installation, resistance to external environmental influences, and, in particular, effective prevention of water ingress into the sensor housing. To this end, according to the invention, the sensor unit can be axially and immovably secured in the sensor housing by means of a retaining ring, which can be positioned on the sensor element and, when the sensor unit is installed in the sensor housing, ultimately rests in a retaining ring receptacle formed between the sensor unit and the sensor housing.

[0008] This fastening method allows for very quick and precise installation at the same time.

[0009] According to an advantageous aspect of the invention, the sensor is sealed using an O-ring, which, when the sensor unit is mounted in the sensor housing, ultimately rests in an O-ring receptacle formed between the sensor package of the sensor unit and the sensor housing. Thus, the entire sensor is sealed. The sensor element, embedded in the sensor package, is protected from external influences. Due to the O-ring between the sensor package, the sensor unit, and the sensor housing, substances, particularly water, are effectively prevented from entering the interior of the sensor housing.

[0010] To enable the installation of the O-ring to produce the seal described above to be performed simultaneously with the installation of the sensor unit in the sensor housing, a highly advantageous aspect of the invention proposes that the sensor housing has a radially inwardly projecting edge, and the sensor package of the sensor unit has a radially outwardly projecting stepped portion, such that when the sensor unit is installed in the sensor housing, the edge and the stepped portion can be spaced apart in a predefined manner in the radial direction of the sensor housing, thereby creating an annular circumferential cavity forming the O-ring housing. This edge and stepped portion position the O-ring in the O-ring housing during the installation of the sensor unit in the sensor housing by means of a retainer, as will be described in more detail below. In this case, it is particularly advantageous that the spacing between the edge and the stepped portion can be predefined based on the material properties of the O-ring, particularly its elasticity. The O-ring has a dual function. It is responsible for the waterproof seal of the connection and also provides an elastic preload to the connection. In this case, the O-ring housing is configured such that the O-ring is compressed at least in the axial direction, i.e., parallel to the axis of the tubular sensor housing, or in both the axial and radial directions.

[0011] An advantageous aspect of the invention proposes that the sensor housing has a first annular circumferential groove at a predetermined position in its inner wall, and the sensor package of the sensor unit has a second annular circumferential groove, the second groove being positioned such that when the sensor unit is mounted in the sensor housing, the first groove and the second groove are opposite each other, and the resulting annular circumferential cavity forms a retaining ring.

[0012] The retaining ring creates an interlocking connection between the sensor housing and the sensor package, and closes the force loop with respect to the O-ring. The retaining ring is configured to be compressed and stretched in the radial direction, i.e., perpendicular to the axis of the tubular sensor housing, to facilitate the mounting process described below. The retaining ring is rigid in the axial direction to ensure sufficient support to withstand the compressive forces of the O-ring. Depending on the stability requirements of the sensor element during temperature variations, the retaining ring can be made of either plastic or metal. For example, with a plastic retaining ring, the packaged sensor element can move ±15 µm over a temperature range of -50°C to 120°C. For a metal retaining ring, this movement can be reduced to ±2 µm.

[0013] A particularly advantageous aspect of the invention proposes that the retaining ring has a truncated conical chamfer pointing inwards from the sensor housing, wherein the axis of the truncated conical chamfer coincides with the axis of the sensor housing. This greatly facilitates the installation process, which will be described in more detail below.

[0014] To make the installation process easier, another advantageous aspect of the invention proposes that the sensor package has a truncated conical chamfer pointing inwards from the sensor housing, wherein the axis of the truncated conical chamfer coincides with the axis of the sensor housing.

[0015] According to the present invention, a method for mounting a sensor unit in a sensor housing of a sensor as described above is characterized by the following steps:

[0016] - Install the retaining ring in the second groove of the annular circumference of the sensor package;

[0017] - Push the sensor unit into the interior of the tubular sensor housing until the retaining ring expands into the first circumferential groove in the inner wall of the sensor housing.

[0018] According to another method for mounting a sensor unit in a sensor housing, the present invention provides the following steps:

[0019] - Install the retaining ring in the first annular circumferential groove in the inner wall of the sensor housing;

[0020] - Push the sensor unit into the interior of the tubular sensor housing until the retaining ring finally rests in the second groove of the annular circumference of the sensor package.

[0021] Both mounting methods utilize sensor encapsulation, which enables the sensor unit to be mounted in the sensor housing very quickly and accurately through the interaction of a first groove extending circumferentially in the inner wall of the sensor housing and a second groove extending circumferentially in the sensor encapsulation.

[0022] To achieve effective sealing of the sensor in both mounting methods, one inventive aspect of the mounting method proposes that, before or after installing the retaining ring in the second annular circumferential groove in the sensor package or the first annular circumferential groove in the inner wall of the sensor housing, an O-ring is installed on an outwardly projecting stepped portion of the sensor package. This is such that when the sensor unit slides into the sensor housing, the O-ring deforms to create a seal, and after the retaining ring has been positioned in its retaining ring housing, it finally rests in an O-ring housing formed between the sensor package and the sensor housing. In this case, as described above, the distance between the radially inwardly projecting edge of the sensor housing and the radially outwardly projecting stepped portion of the sensor package depends on the material properties of the O-ring to ensure the desired compression of the O-ring, allowing the O-ring to apply the desired force. Attached Figure Description

[0023] Exemplary embodiments of the present invention are illustrated in the accompanying drawings and explained in more detail in the following description.

[0024] Figure 1 A schematic cross-sectional view of the front portion of the sensor according to the present invention is shown;

[0025] Figure 2 An enlarged section of the front portion of the sensor according to the present invention is shown;

[0026] Figure 3a , Figure 3b The cross-sectional and plan views of the buckle are shown respectively;

[0027] Figure 4 The mounting of the retainer on the sensor package of the sensor unit is illustrated schematically;

[0028] Figures 5a to 5e The method steps of one configuration of the present invention for mounting a sensor unit in a sensor housing are shown;

[0029] Figures 6a to 6d The steps of another configuration of the method of the present invention for mounting a sensor unit in a sensor housing are shown. Detailed Implementation

[0030] Figure 1 A cross-sectional view of the front portion of a sensor according to the invention is schematically illustrated. The sensor includes a sensor housing 100, which may have, for example, external threads. A sensor unit 200 is secured inside the sensor housing. The sensor unit 200 has a circuit board 220 on which circuitry (not shown) for evaluating the signal of a sensor element 215 is arranged. The sensor element 215 is encapsulated in a potting compound, hereinafter referred to as sensor package 210. Figure 1As illustrated, the sensor unit 200 is secured inside the tubular sensor housing 100, specifically such that the front movable end face 202 of the sensor terminates flush with the front end of the sensor housing 100. In this case, the securing is achieved by means of a retaining ring 400 arranged in a retaining ring housing formed by two opposing annular circumferential grooves. A first annular circumferential groove 140 is arranged in the inner wall of the sensor housing 100, and a second annular circumferential groove 240 is arranged at a location in the sensor package 210 opposite to groove 140 when the sensor unit 200 is mounted in the sensor housing 100, thereby forming a retaining ring housing together with the groove. The retaining ring 400 itself has a truncated conical chamfer 410 pointing inwards from the sensor housing 100, wherein the axis of the truncated conical chamfer 410 coincides with the axis of the sensor housing 100. Figure 1 and Figure 2 As is clearly seen, when the sensor unit 200 is mounted in the sensor housing 100, the retaining ring 400 is located in the retaining ring receptacle formed by the grooves 140 and 240. Particularly important in this case is the overlap 490 between the front portion of the retaining ring and the groove wall of the groove 240. In this way, the sensor package 210 is securely held in the sensor housing 100 in the axial direction. The retaining ring 400 creates an interlocking connection between the sensor housing 100 and the sensor package 210, and closes the force loop regarding the compressive force of the O-ring 300. This compressive force is generated by the deformation of the O-ring 300. (As in...) Figure 1 and Figure 2 As illustrated, an O-ring 300 is arranged in an O-ring housing defined by a radially outwardly projecting stepped portion 230 of the sensor package 210 and a radially inwardly projecting edge 130 in the sensor housing. In the installed state, the radially outwardly projecting stepped portion 230 and the radially inwardly projecting edge 130 have a mutual spacing that can be predefined by the material properties of the O-ring 300, particularly its elasticity. Due to the deformation of the O-ring 300, a force is applied not only in the radial direction but also in the axial direction. In particular, the force applied in the axial direction interacts with the retaining ring 400 to securely fasten the sensor unit 200 axially within the sensor housing 100, and especially to seal the sensor unit 200 within the sensor housing 100. Figure 3a ), Figure 3bThe retaining ring, shown in plan and cross-sectional views, can be made of, for example, metal or plastic, depending on the required stability of the sensor element 215 during temperature variations. With respect to the plastic retaining ring 400, the encapsulated sensor element 215 can move ±15 µm. With respect to the metal retaining ring 400, this movement can be reduced to ±2 µm. It should be emphasized that both the O-ring housing formed by the stepped portion 230 and the edge 130 and the retaining ring housing formed by the grooves 240 and 140 need to be selected in terms of size such that, particularly with respect to the compression of the O-ring 300 and the associated force ratio described above, the sensor package 210, and thus the entire sensor unit 200, is securely fastened within the sensor housing 100.

[0031] Figure 4 The retaining ring 400 is schematically illustrated to be fastened to the sensor package 210. The retaining ring 400 is pushed sideways upward onto the sensor package 210 until it finally rests in the groove 240.

[0032] refer to Figure 5a )to Figure 5b A method for mounting a sensor unit 200, i.e., a sensor package 210, into a sensor housing 100 is schematically illustrated. The sensor unit 200, i.e., the sensor package 210, and the circuit board 220 connected thereto are pushed into the interior of the sensor housing 100 from the left side in the direction of the arrow marked R in FIG. 5. In this case, an O-ring 300 rests on the stepped portion 230 of the sensor package 210. A retaining ring 400 is positioned in a groove 240 as described above. The retaining ring 400 can be easily guided into the interior of the housing by means of a chamfer 410.

[0033] In this regard, it should be noted that, with Figure 4 Different from the option illustrated by mounting the retaining ring 400 onto the sensor package 210, it is also possible to push the retaining ring 400 axially from the printed circuit board 220 onto the sensor package 210. For this purpose, the sensor package 210 has a truncated taper chamfer 250 pointing inwards towards the sensor housing 100, the axis of which coincides with the axis of the sensor housing 100.

[0034] Figure 5b The following step illustrates the next installation procedure. If the outer diameter of the retaining ring 400 is larger than the inner diameter of the housing opening in the sensor housing 100, the chamfer 410 makes it easier for the retaining ring 400 to slide into the interior of the sensor housing 100. Figure 5b In the sensor housing 100, the buckle 400 slides completely into the interior of the sensor housing 100 and abuts against the inner wall of the sensor housing. Figure 5bThe image shows the state where the seal 300 finally abuts against the front opening of the sensor housing 100. The sensor unit 200 is further pushed into the interior of the sensor housing 100 along direction R, where the sensor unit now finally abuts against edge 130. Due to the chamfer 410, the retaining ring 400 deforms and slides across edge 130, as... Figure 5d As shown in the image. Figure 5c )and Figure 5d As shown, the O-ring 300 has been deformed, and due to the stepped portion 230, the O-ring moves along with the sensor package 210 when it is pushed into the interior of the sensor housing 100. Figure 5e This illustrates the final mounting state of sensor package 210 and therefore sensor unit 200 within sensor housing 100. The retaining ring 400 is now located in grooves 140 and 240, which together form a retaining ring receptacle. The O-ring 300 is deformed in a desired manner and is located in the space formed by the radially inwardly projecting edge 130 of sensor housing 100 and the radially outwardly projecting stepped portion 230 of sensor package 210. In this case, the edge 130 and the stepped portion 230 have a defined and desired mutual spacing. Figure 5e As shown, the overlap 490 between the retaining ring 400 and the sensor package 210 is used to securely fasten the sensor unit 200 to the sensor housing 100. It should be noted that the maximum diameter of the groove 140 in the inner wall of the sensor housing 100 is smaller than the outer diameter of the undeformed retaining ring 400, so that the retaining ring 400 still exhibits a certain amount of deformation after being engaged. This prevents the retaining ring 400 from moving radially after installation. The retaining ring 400 is effectively fixedly connected to the housing 100. The dimensions of the housing, particularly the dimensions of the groove 140 therein, and the inwardly projecting edge 130, the dimensions of the retaining ring 400 and the sensor package 210, particularly the outwardly projecting stepped portion 230 and the dimensions of the groove 240 in the sensor package 210, are selected such that the O-ring 300 is in a compressed state during installation. In this case, it can be said that the O-ring 300 attempts to push the packaged sensor element, i.e., the sensor package 210, out of the interior of the housing.

[0035] Figure 6a )to Figure 6d This illustrates another configuration of the mounting method according to the invention. In this case, in the first method step, the retaining ring 400 is not initially fastened to the sensor package 210, but rather fastened in the groove 140 of the sensor housing 100. This initial state is... Figure 6aAs illustrated in ( ). In this case, the retaining ring 400 has a chamfer 420 pointing in the opposite direction of the pushing direction R. The sensor package 210, i.e., the sensor unit 200, is pushed into the interior of the sensor housing 100 along the direction R. During this process, the O-ring 300 slides into the interior of the sensor housing 100. In step 6b), the chamfer 250 of the sensor package 210 abuts against the chamfer 420 of the retaining ring 400. The O-ring 300 has been pushed into the interior and deformed by means of the stepped portion 230. The sensor package 210 is further pushed into the interior of the sensor housing 100 along the direction R, and during this process, the retaining ring 400 slides into the groove 240 of the sensor package 210. In the final installed state ( Figure 6d The retaining ring 400 is located in a retaining ring housing formed by grooves 140 and 240, where, similarly, there should again be an overlap 495 between the end face of the retaining ring 400 opposite to the groove wall of groove 140 and the retaining ring 400. In this case, the O-ring 300 in the O-ring housing formed by the stepped portion 230 and the edge 130 is deformed again to the desired degree and a compressive force is applied, which can be said to attempt to remove the sensor unit 200 from the housing 100; however, this is not possible due to the retaining ring 400 and the mentioned overlap 495. This forms a secure axial connection between the sensor unit 200 and the sensor housing 100.

Claims

1. A sensor having a tubular sensor housing (100) and a sensor unit (200) that can be fastened inside the sensor housing (100), characterized in that, The sensor unit (200) can be axially and immovably secured in the sensor housing (100) by means of a retainer (400) which can be positioned on the sensor package (210) and, when the sensor unit (200) is installed in the sensor housing (100), the retainer is ultimately resting in a retainer receptacle formed between the sensor package (210) and the sensor housing (100).

2. The sensor according to claim 1, characterized in that, The sensor is sealed by means of an O-ring (300), and when the sensor unit (200) is installed in the sensor housing (100), the O-ring is finally placed in an O-ring holder between the sensor package (210) of the sensor unit (200) and the sensor housing (100).

3. The sensor according to claim 1 or 2, characterized in that, The sensor housing (100) has a radially inwardly projecting edge (130), and the sensor package (210) of the sensor unit (200) has a radially outwardly projecting stepped portion (230), such that when the sensor unit (200) is mounted in the sensor housing (100), the edge (130) and the stepped portion (230) are spaced apart in a predefined manner in the radial direction of the sensor housing (100), thereby creating an annular circumferential cavity forming the O-ring housing.

4. The sensor according to claim 3, characterized in that, The distance between the edge (130) and the stepped portion (230) can be pre-defined based on the material properties of the O-ring (300), particularly its elasticity.

5. The sensor according to claim 1, characterized in that, The sensor housing (100) has a first annular circumferential groove (140) at a predetermined position in the inner wall, and the sensor package (210) of the sensor unit (200) has a second annular circumferential groove (240) positioned such that when the sensor unit (200) is mounted in the sensor housing (100), the first groove (140) is opposite to the second groove (240), and the resulting annular circumferential cavity forms the retaining ring.

6. The sensor according to claim 1, characterized in that, The buckle (400) has a truncated tapered chamfer (410, 420) in the pushing direction (R) and / or against the pushing direction (R), wherein the axis of the at least one truncated tapered chamfer (410, 420) coincides with the axis of the sensor housing (100).

7. The sensor according to any one of the preceding claims, characterized in that, The buckle (400) is made of plastic or metal.

8. The sensor according to any one of the preceding claims, characterized in that, The sensor package (210) has a truncated conical chamfer (250) pointing toward the interior of the sensor housing (100) in the pushing direction (R), wherein the axis of the truncated conical chamfer (250) coincides with the axis of the sensor housing (100).

9. The sensor according to any one of the preceding claims, characterized in that, The sensor housing (100) has a chamfer (150) on its end face opening.

10. A method for mounting a sensor unit (200) in a sensor housing (100) of a sensor according to any one of claims 1 to 9, characterized in that, The following steps: - Install the retaining ring (400) in the second annular circumferential groove of the sensor package (210); - Push the sensor unit (200) into the interior of the tubular sensor housing (100) until the retainer (400) expands into the annular circumferential first groove (140) in the inner wall of the sensor housing (100).

11. A method for mounting a sensor unit (200) in a sensor housing (100) of a sensor according to any one of claims 1 to 9, characterized in that, The following steps: - Install the retaining ring (400) in the annular circumferential first groove in the inner wall of the sensor housing (100); - Push the sensor unit (200) into the interior of the tubular sensor housing (100) until it is finally placed in the second circumferential groove of the sensor package (210).

12. The method according to claim 10 or 11, characterized in that, Before or after mounting the retaining ring (400) in the second annular circumferential groove of the sensor package (210) or in the first annular circumferential groove in the inner wall of the sensor housing (100), the O-ring is mounted on the outwardly projecting stepped portion of the sensor package (210) such that when the sensor unit (200) is pushed into the sensor housing (100), the O-ring deforms to create a seal, and after the retaining ring (400) has been positioned in the retaining ring receptacle, it is finally placed in the O-ring receptacle formed between the sensor package (210) and the sensor housing (100).

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