CN113906526A

CN113906526A - Device for reducing mechanical loads below and in a functional component, such as a PTC element

Info

Publication number: CN113906526A
Application number: CN202080040223.4A
Authority: CN
Inventors: M·乌尔巴内克; T·施塔尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-05-31
Filing date: 2020-05-26
Publication date: 2022-01-07
Also published as: DE102019207983A1; KR20220016135A; WO2020239735A1

Abstract

The invention relates to a device for reducing mechanical loads below and in a functional component (22), in particular a PTC element. The functional component is arranged between the flow-guiding element (20) having the cover (14) on the one hand and the thermal mass (24) on the other hand. The fastening device (10) has a flat or concavely curved contact side (32) in the central section (12). The contact side acts on the upper side (18) of the cover (14) in the clamped state (30) of the fastening device (10). The first contact region (34) and the second contact region (36) are separated from one another by a bulge (38) in the material of the intermediate part (12) of the fastening device (10) designed as a spring clip. By forming the first contact region (34) and forming the second contact region (36), the holding force is distributed and the absolute height of the maximum value of the contact pressure is significantly reduced.

Description

Device for reducing mechanical loads below and in a functional component, such as a PTC element

Technical Field

The invention relates to a device for reducing mechanical loads below and in a functional component which is arranged between a flow-guiding element having a cover on the one hand and a thermal mass on the other hand. The invention further relates to the use of the device as a fastening device for at least one heating element for tempering or melting operating/auxiliary materials.

Background

In order to melt the operating/auxiliary material, for example a freezable aqueous urea solution, electrically operated heaters with positive temperature coefficient elements (PTC elements) are used, in particular in the field of exhaust gas aftertreatment. Such positive temperature coefficient elements are fixed in the mass for heat dissipation and heat dissipation, for example in the cooling body, for example by caulking (Verstemmen), i.e. by plastic deformation of the recesses. Another possibility for fastening the ptc element is provided by a spring steel clip, by means of which the assembly consisting of the ptc element, a flow-conducting component, for example a flow-conducting rail, and an electrical insulating element serving as a cover is pressed directly onto the heat sink as an assembly surrounded by the spring steel clip.

In this fixation technique it has been demonstrated that: for functional, geometric or manufacturing reasons, the holding force, which is applied, for example, by a spring clip, is pressed onto the ptc element in such a way that the holding force acts only in a point-like manner and is not dissipated. This leads to harmful stress peaks which can occur in the material of the ptc element thus fixed. In addition, it has been confirmed that: the contact pressure distribution achieved by means of the spring clip and acting non-planarly is also disadvantageous for heat dissipation.

Disclosure of Invention

According to the invention, a device for reducing mechanical loads below and in a functional component, for example a ptc element, which is arranged between a flow-guiding element having a cover on the one hand and a thermal mass on the other hand, is proposed. The fastening device has a flat or concavely curved contact side in the middle section, which contact side acts on the upper side of the cover in the clamped state of the fastening device.

The solution proposed according to the invention makes it possible to significantly reduce the harmful mechanical stresses that are permanently exerted on the material of the functional component. A further advantage of the solution proposed according to the invention can be that the function of heat dissipation is significantly improved with respect to the functional component thus fixed.

In a development of the solution proposed according to the invention, the fixing device is realized in particular as a spring clip.

In the solution proposed according to the invention, in the clamped state of the fastening device, a first contact region and a second contact region are formed between the contact side of the fastening device and the preferably convexly curved upper side of the cover.

In the solution proposed according to the invention, in the clamped state of the fixing device, the first contact region and the second contact region are separated by the bulge in the middle section of the fixing device. By forming the first contact region and the second contact region, a force acting in each of the two contact regions is reduced in terms of an absolute height thereof; furthermore, by forming two contact areas it is advantageously possible to achieve: the contact pressure acting on the functional component can be distributed significantly more uniformly over the functional component and the structural elements located therebelow. This in turn facilitates the attenuation of stress peaks and, in addition, the homogenization of the pressure distribution in the material used for producing the functional component, for example, designed as a ptc element. In a development of the solution proposed according to the invention, the fixing device comprises a first connecting plate and a second connecting plate, which can extend laterally of the middle part and, for example, parallel to each other. The first and second connecting plates, which extend laterally to the central part, are embodied in such a way that the window formed in the central part is hooked into a hook formed, for example, on the thermal mass and deforms the bendable central part. The webs do not necessarily have to run parallel to one another, but they can also be formed so as to be rotated by a small angle relative to one another. The following possibilities exist here: only one connecting plate is formed on the spring clamp and one projection of the thermal mass is used as a clamping point.

In the solution proposed according to the invention, the possibility exists for the cover (which covers the flow-guiding element with lateral projections) to be produced as an injection-molded part from a plastic material with electrically insulating properties. This makes it possible to already produce a convexly curved upper side, i.e. a curved profile, which is opposite the contact side of the fastening device when the cover is produced, without requiring a further work step when the cover is produced. Alternatively, the following possibilities exist: the cover is embodied as a ceramic plate covering the flow-guiding element.

In the solution proposed according to the invention, the cover of the functional component is designed in such a way that it projects beyond the functional component with a lateral projection. The area of the flow-guiding element is larger than the area of the functional component in order to ensure that: the entire side of the functional member is electrically contacted. This also applies to the case in which the side is coated with a material that conducts heat well, in order to improve the heat extraction towards the side. The lateral extensions also provide the advantage that the flow-guiding element is better protected against contact with the fastening device and the thermal mass and thus serves as a protective measure against short circuits. The current should flow only from the current-conducting element through the functional component into the thermal mass.

With the solution proposed according to the invention, in the clamped state of the fixing device, there is a pressure distribution extending substantially rectangularly therein below the functional component to be fixed. The mechanical loading of the functional component to be fastened is significantly reduced by this pressure distribution, and the maximum of the pressure peaks formed is homogenized on the basis of the pressure distribution.

The invention further relates to the use of the device as a fastening device for at least one heating element for tempering or melting operating/auxiliary materials for the aftertreatment of exhaust gases of an internal combustion engine in an exhaust gas aftertreatment system.

The invention has the advantages that:

the advantage of the solution proposed according to the invention can be seen primarily in the fact that a more favorable distribution of the retaining forces acting on the functional component to be fixed can be achieved with this solution. Furthermore, an improved contact pressure distribution between the functional component and the thermal mass can be achieved, in particular a significant increase in the area of mutual contact and a reduction in the absolute height of the occurring pressure peaks. This facilitates a reduction of mechanical stresses in the functional component, in particular the ptc element. Since the stress level in the functional component is significantly reduced, the service life of the functional component can be significantly extended during the downtime of an exhaust gas aftertreatment system, for example for the exhaust gases of an internal combustion engine.

With the solution proposed according to the invention, in the two contact regions between the fastening device and the cover (which covers the flow-guiding element), instead of a single point contact or an existing contact, two contact regions are formed which are separated from one another, i.e. do not interact with one another, as a result of which the absolute height of the mechanical load is significantly reduced and the pressure distribution in the functional component to be fastened is homogenized to a particularly great extent.

On account of the homogenization of the retaining force introduced onto the functional component to be fastened, the heat extraction of the functional component is also improved and, overall, the mechanical stresses that impair the functional component over its service life are significantly reduced at its maximum level.

The solution proposed according to the invention offers on the one hand the advantage of low mechanical stresses in the more sensitive and more brittle functional component and the advantage of a more uniform contact pressure distribution between the functional component and the thermal mass. The first-mentioned advantages reduce the risk of fractures in the material of the functional element or increase the service life expectancy of the functional element and/or allow higher clamping forces to be applied without component damage. The second mentioned advantage leads to an improved and uniform heat transfer from the functional component, for example a ptc element, to the thermal mass. This increases the thermal power and allows fluctuations in thermal power among the plurality of heaters to be reduced.

Drawings

The invention is described in more detail below with reference to the accompanying drawings.

The figures show:

fig. 1 a fixing device according to the invention in a relaxed state;

fig. 2 shows the proposed fixing device according to the invention in a clamped state;

FIG. 3 is a perspective view of the fixture above a cover having a convexly curved upper side;

4.1 and 4.2 stress distribution in functional components with flat configured covers and conventional spring clips;

fig. 5.1 and 5.2 show in fig. 5.1 the pressure distribution which occurs between the fastening device according to the invention and the cover of the guide element at the beginning of the contact and in fig. 5.2 the pressure distribution which occurs between the fastening device according to the invention and the cover of the guide element at the end of the assembly process when the contact is established;

6.1 and 6.2 pressure distribution below the functional component according to FIG. 6.1, and stress distribution in the functional component according to FIG. 6.2;

FIG. 7 shows the course of the first bending line in the case of a conventional spring clip;

fig. 8 is a view of a second bending line of a fastening device designed as a spring clip according to the invention;

FIG. 9 shows an embodiment variant in which the fixing means is clamped to the thermal mass; and

fig. 10 shows an embodiment variant in which the functional component is fixed by means of ceramic plates.

In the following description of embodiments of the invention, identical or similar elements are designated with identical reference numerals, wherein repeated descriptions of these elements in a single instance are omitted. The figures only schematically show the content of the invention.

Detailed Description

Fig. 1 shows the proposed fastening device 10 according to the invention in its relaxed state 28.

As can be gathered from fig. 1, the fastening device 10 proposed according to the invention is embodied, for example, as a spring clip and comprises an intermediate part 12. The intermediate part 12 has a contact side 32 on the side facing the cover 14. In the illustration according to fig. 1, the region of the contact side 32 of the central part 12 is embodied straight. On both sides of the intermediate portion 12, a first connecting plate 82 and a second connecting plate 84 of the fixing device 10 extend parallel to each other.

The fixture 10 is disposed above the cover 14. The lid 14 may have a flat upper side 16 as shown in fig. 1; alternatively, the following possibilities also exist: the cover 14 with the curved upper side 18 is embodied according to a similar view to fig. 3. The cover 14 is made of a plastic material having electrically insulating properties. The cover 14 covers the flow-guiding element 20 arranged thereunder. The flow-guiding element 20 is embodied, for example, as a flow-guiding rail and in turn covers the functional component 22. The functional component 22 is, for example, a positive temperature coefficient element, which serves as a heating device and serves for tempering or melting a freezable operating/auxiliary material, for example a freezable urea-water solution for exhaust gas aftertreatment of an internal combustion engine.

The functional component 22, in particular embodied as a positive temperature coefficient element, is applied to the upper side 26 of the thermal mass 24. Fig. 1 shows a relaxed state 28 of the fastening device 10 designed as a spring clip, while the fastening device 10 is shown in the view according to fig. 2 in a clamped state 30.

Fig. 2 shows the fixing device 10 in the clamped state 30. In the clamped state 30, the fastening device 10 embodied as a spring clip fastens the composite of the cover 14, the flow-guiding element 20 and the functional component 22, which can be a positive temperature coefficient element or the like, to the upper side 26 of the thermal mass 24. As can be seen from fig. 2, the first connecting plate 82 and the second connecting plate 84 of the fastening device 10, which is designed as a spring clip, extend on the side of the thermal mass 24. During assembly, the connecting plates 82, 84 are slightly pressed apart, so that the central part 12 of the fastening device 10 (on which the flat or concavely configured contact side 32 is embodied) comes to bear against the cover 14 having the flat upper side 16. Due to the deformation of the fastening device 10, two contact regions are formed which are separated from one another, namely a first contact region 34 and a second contact region 36, as shown in fig. 2. The first contact region 34 and the second contact region 36 are separated from one another by a bulge 38 in the material of the intermediate part 12 of the fastening device 10 designed as a spring clip. By forming the first contact region 34 and forming the second contact region 36, the holding force is distributed and the absolute height of the contact pressure maximum is significantly reduced. The two

contact regions

34 and 36, which are separated from one another by the bulge 38, indicated in fig. 2, in the material of the central part 12, do not interact, i.e. do not influence one another.

Fig. 3 shows a perspective view of the fastening device 10 in the assembled state on the thermal mass 24. Fig. 3, which is shown in a partially cut-away view and a perspective view, shows that: in this embodiment variant of the solution proposed according to the invention, the cover 14 has a curved upper side 18. The extension in the curved upper side 18 of the cover 14 is indicated by reference numeral 40. The perspective view of fig. 3 (also in quarter section) can be seen: the lid 14 is injection moulded from a plastics material. When producing the cover 14, which covers the flow-guiding element 20 in the projection 42, the convexly curved upper side 18 can already be produced during production without further processing.

Fig. 3 shows: in this embodiment variant of the solution proposed according to the invention, the cover 14 laterally covers the flow-guiding element 20, which is designed, for example, as a flow-guiding rail, in the projection 42. The cover 42 of the side faces extends in the x-y plane according to fig. 3.

It can also be seen from the illustration according to fig. 3 that in the assembled state of the fastening device 10, i.e. in the clamped state 30, a first contact region 34 and a second contact region 36 are formed in the central part 12 of the fastening device 10. The two

contact regions

34, 36 are separated from one another by a bulge 38 which is present in the material of the central part 12. The first contact region 34 and the second contact region 36 between the contact side 32 of the central part 12 and the convexly curved upper side 18 of the cover 14 bring about a homogenization of the introduction of the retaining force into the functional component 22, which may be configured, for example, as a ceramic component or as a positive temperature coefficient element.

Fig. 4.1 and 4.2 show the pressure distribution or stress distribution 58 in the functional component 22.

Fig. 4.1 shows an exemplary pressure distribution below the functional component 22, while fig. 4.2 shows a stress distribution 58 occurring in the material of the functional component 22.

Fig. 4.1 shows how, in the case of a conventional spring clip on the functional component 22 (the underside 78 of the functional component is shown here), two

contact pressure regions

44 and 46 with high local maxima occur along the edge of the functional component 22. The contact pressure between these contact pressure concentration zones is as low as zero. The upper side of the functional component 22 is marked with the reference number 80 in the view according to fig. 4.1. Fig. 4.2 shows that, in the material of the functional component 22 (which is shown here from its upper side 80), higher stresses occur in the region of the first contact pressure region 44 and the second contact pressure region 46, provided that the cover 14 is produced with the flat upper side 16 shown in fig. 1 and 2. Fig. 5.1 and 5.2 show the mechanical loads that occur when the fastening device 10 proposed according to the invention is fitted to the curved upper side 18 of the cover 14.

Fig. 5.1 shows, for example: in the first contact phase 48 (in which the fastening device 10 is applied from above), the two webs 82, 84 extending parallel to one another diverge in a similar direction of movement 52 and produce the contact surface 50 in the first contact phase 48. The contact surface is formed between the contact side 32 of the intermediate part 12 of the fixing device 10 and the upper side 18 of the cover 14. The fastening device 10 is shown in a cut-away view in fig. 5.1. Fig. 5.1 shows a first assembly phase of the fastening device 10 in the direction of movement 52.

Fig. 5.2 shows a first assembly phase of the fastening device 10 according to the invention with a flat or concavely curved contact side 32. In the clamped state 30 of the fastening device 10 (which is illustrated here as a partially broken-away spring clip) illustrated in fig. 5.2, the first contact region 34 and the second contact region 36 occur in the second contact phase 54. In the state shown in fig. 5.2, the contact side 32 contacts the cover 14 with the curved upper side 18 in the middle part 12 of the fixing device 10, which means that: in the clamped state 30, the contact side 32 of the fastening device 10 fastens the cover 14 with the components located thereunder, such as, for example, the flow-guiding element 20 and the functional component 22 in a composite body. The holding forces occurring in the two contact regions, namely the first contact region 34 and the second contact region 36, are distributed substantially linearly according to the solid half-section in fig. 5.2.

Fig. 6.1 and 6.2 schematically show the pressure and stress distributions 58 that occur in the functional component 22 when the solution proposed according to the invention is used. Fig. 6.1 shows: a substantially rectangularly extending pressure distribution 56 occurs on the underside 78 of the functional component 22. The functional component 22 with its upper side designated by reference numeral 80 is shown in the view according to fig. 6.1 from its lower side 78.

In contrast, fig. 6.2 shows the functional component 22 from its upper side 80. In fig. 6.2, a uniformly extending stress distribution 58 is shown, which is more uniform within the material of the functional component 22, which can be, for example, the already mentioned positive temperature coefficient element.

For the two views according to fig. 6.1 and 6.2: the fastening device 10 with its contact side 32 is embodied flat or concavely arched, while the cover 14 covering the functional component 22 comprises the above-described convexly curved upper side 18. For this application, on the one hand, a substantially rectangularly extending pressure distribution 56 occurs below the functional component 22, and on the other hand a significantly smaller stress distribution 58 occurs in the functional component 22, as is shown in connection with fig. 6.2.

Fig. 7 shows the trend of the first bending line 60 of the fastening device 66 with the convex contact side 32.

From the illustration according to fig. 7, it can be seen that the beam length is

The amount of flex 64 is plotted at 62. If the conventional fastening device 66 (i.e., the intermediate portion 12 having a convex curvature) is relaxed, a relaxed state 70 occurs. Once the fixture 66 having the convex midsection 12 is clamped, only the contact area in the clamped state 72 is present.

In contrast, fig. 8 shows a second bending line 65, according to which the bending amount 64 is plotted over the beam length 62.

Fig. 8 shows a fastening device 10 according to the invention, the contact side 32 of which is embodied with a flat central section 12 or a concavely curved central section 12. In the transition of the fastening device 68 with the flat or concavely curved middle section 12 from the relaxed state 74 into the clamped state 76, the contact region, i.e. the first contact region 34 or the second contact region 36, occurs as described above with reference to fig. 2 and 3.

The clamped state 30 of the fastening device 10 can be seen from the illustration according to fig. 9. There is a window 86 in one of the webs 82, 84 of the fixture 10 (which is configured as a spring clip). Hook-shaped projections 88 project into windows 86 in the material of the fixture 10, which projections are located on the sides of the thermal mass 24. End 92 of fixture 10 is clamped under protrusion 90 of thermal mass 24 at clamping point 94. Due to the clamped state 30 shown in fig. 9, a bulge 38 shown in fig. 9 occurs in the region of the central part 12 (which is here configured straight). A first contact region 34 and a second contact region 36 separated therefrom by a bulge 38 are thus formed, here between the flat upper sides 16 of the covers 14.

As can be seen from the illustration according to fig. 10, in the clamped state 30 of the fastening device 10 shown in fig. 10 (also embodied here as a spring clip), the functional component 22 fastens the functional component 22 to the upper side 26 of the thermal mass 24 with the ceramic plate 96 and the flow-guiding element 20 connected in between (for example in the flow-guiding rail configuration). In the clamped state 30 of the fastening device 10, the bulge 38 of the central part 12 also occurs here in the region of the central part 12, which is designed straight, so that the first contact region 34 and the second contact region 36 occur on both sides of the bulge 38.

Furthermore, fig. 10 shows that the flow-guiding element 20, like the ceramic sheet 96 covering it, also has an excess 42 with respect to the dimensions of the covered functional component 22. This makes it possible to homogenize the current and to pass the current from the current-guiding element 20 via the functional component 22 into the thermal mass 24 while avoiding short circuits. The projection 42 can bring about an evenly distributed contact in the region of the edge touching the functional component 22.

The present invention is not limited to the embodiments described herein and the aspects highlighted therein. But that several variants are possible within the scope of protection given by the claims, which variants are within the scope of the treatment of the person skilled in the art.

Claims

1. A device for reducing mechanical loads below and in a functional component (22), in particular a positive temperature coefficient element, which is arranged between a flow-guiding element (20) with a cover (14) and a thermal mass (24), characterized in that a fixing device (10) has a flat or concavely curved contact side (32) in a middle section (12), which in the clamped state (30) of the fixing device (10) loads an upper side (18) of the cover (14).

2. Device according to claim 1, characterized in that the fixing means (10) are embodied as spring clips.

3. Device according to claim 1, characterized in that in the clamped state (30) of the fixing device (10) a first contact area (34) and a second contact area (36) are formed between the contact side (32) and the convexly curved upper side (18) of the cover (14).

4. A device according to claim 3, characterized in that in the clamped state (30) of the fixing device (10) the first contact area (34) and the second contact area (36) are separated from each other in the intermediate portion (12) by a bulge (38).

5. The device according to claim 2, characterized in that the fixing device (10) has a first connecting plate (82) and a second connecting plate (84).

6. Device according to claim 1, characterized in that the cover (14) is manufactured as an injection-molded piece from a plastic material having electrically insulating properties.

7. The device according to claim 1, characterized in that the cover (14) is embodied as a ceramic plate (96) covering the flow-guiding element (20).

8. Device according to claim 6, characterized in that the cover (14) exceeds the functional component (22) with an excess (42).

9. Device according to claim 1, characterized in that in the clamped state (30) of the fixing device (10) there is a substantially rectangularly extending pressure distribution (56) below the functional component (22).

10. The device according to claim 1, characterized in that in the clamped state (30) of the fixing device (10) there is a uniform, large-area contact pressure distribution on the functional component (22) without a distinct maximum.

11. Device according to claim 1, characterized in that in the clamped state (30) of the fixing device (10) there is a low level of mechanical stress in the functional component (22).

12. Use of a device according to one of the preceding claims as a fastening device for at least one heating element for tempering or melting of an operating/auxiliary material for the aftertreatment of exhaust gases of an internal combustion engine by means of an exhaust gas aftertreatment system.

13. A heating assembly having at least one heating element for tempering or melting of an operating/auxiliary material for the aftertreatment of exhaust gases of an internal combustion engine by means of an exhaust gas aftertreatment system, wherein the at least one heating element is fixed as a functional device by means of an arrangement according to any one of claims 1 to 11.