GB2462152A

GB2462152A - Circuit board mounting in a housing

Info

Publication number: GB2462152A
Application number: GB0903478A
Authority: GB
Inventors: Marcin Rejman
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-02-29
Filing date: 2009-02-27
Publication date: 2010-02-03
Anticipated expiration: 2029-02-27
Also published as: CN101522009A; GB0903478D0; GB2462152B; KR20090093866A; DE102008000442A1

Abstract

A lower housing part (21) and an upper housing part (22) are fixed together by a self tapping screw fastening element (42). A circuit board (29) is clamped between first and second support sections (32, 38) of the upper and lower housing parts. Resilient inserts (eg 43) may be provided between the circuit board and the housing support or between the support projection 34 and the circuit board to increase vibration resistance.

Description

CIRCUITBOARD ARRANGEMENT

The present invention relates to a circuitboard arrangement.

Fastening of circuitboards in multi-part housings are currently realised in many ways.

Thus, it is known to fix a circuitboard with the help of a snap connection in one of the housing parts. Tolerance problems with this mode of fastening frequently lead to an excessively loose circuitboard seat, so that an insufficient mechanical strength with respect to shock-like loading, due to, for example, falling from a critical height results.

Beyond that, snap connections of that kind have a low resistance to vibration, particularly when the circuitboard carries heavy electronic components. As a result, in the case of unfavourable natural frequencies the circuitboard can resonate and thereby be damaged.

Apart from snap connections screw connections are known, in which case the circuitboard is penetrated by a fastening screw and the fastening screw is screwed into an internal thread of a screw dome. In the known screw connections the screw head rests directly on the circuitboard. Constructions of that kind, like the afore-described snap construction, do not have a stiffening effect relative to the entire housing. Moreover, it is necessary to fix housing parts of the housing containing the circuitboard to one another by way of additional fastening screws.

A further known fastening possibility is shown in Fig. 2 of the accompanying drawings, in which a housing 5 is composed of a lower first housing part 1 of plastics material and an upper second housing part 2, similarly of plastics material. An integral first support section 4 projects radially inwardly from a first outer wall 3 of the first housing part I into the housing 5, the housing parts 1, 2 of which are constructed as housing shells. Resting on the first support section 4 is a circuitboard 6 which is pressed against the first support section 4 by a second support section 7 opposite the first support section 4 and is formed at a second outer waIl 8 of the second housing 2. The clamping force for clamping the circuitboard 6 between the end faces of the two support sections 4 and 7 is produced by a fastening screw 9, which penetrates a first screw dome 10 of the first housing part 1 and is screwed into an internal thread 11 of a second screw dome 12 of the second housing part 2. It is disadvantageous with this circuitboard arrangement that on the one hand an insufficient mechanical strength of the circuitboard arrangement and on the other hand a too-low resistance to vibration result. The circuitboard 6, like the other afore-described known circuitboard arrangements, does not have a stiffening effect relative to the entire housing. This runs contrary to the desire, for cost and environmental advantages, for increasingly thinner housing wall thicknesses.

The invention therefore has the object of providing a circuitboard arrangement in which the circuitboard is integrated into the housing concept and has a stiffening effect on the housing.

According to the present invention there is provided a circuitboard arrangement comprising a housing, which comprises a first housing part and at least one second housing part fixed to the first housing part by means of at least one fastening element, and a circuitboard clamped between a first support section of the first housing part and a second support section of the at least one second housing part, the fastening element being arranged to engage both support sections.

In a preferred embodiment the circuitboard is integrated into the housing concept in that mutually opposite, preferably dome-shaped support sections receiving the circuitboard axially therebetween are directly loaded by force by the fastening element. The fastening element fixing the housing parts to one another is not, as in the state of the art, arranged at a spacing from the two support sections, but directly engages these and thereby directly loads the two support sections by a clamping force acting on the circuitboard. The circuitboard is as a consequence clamped in place between the support sections as soon as the two support sections are fixed to one another with the help of the fastening element, preferably a clamping element. In a circuitboard arrangement (circuitboard fastening) constructed in accordance with this concept the stiffness and the mechanical stability of the circuitboard is incorporated into the housing stiffness or stability. As a result, the housing, which in particular is constructed from plastics material, can be used more rationally, i.e. the employed quantity of material, particularly plastics material, can be (considerably) reduced, whereby the stiffness and mechanical stability of the actual housing is less. Compensation for this detraction from stiffness and mechanical stability is provided by way of the circuitboard itself. A further advantage consists in that the resistance to vibration is substantially increased. Of particular advantage is an embodiment of the circuitboard arrangement in which not only two mutually opposite support sections fixed to one another by a fastening element are provided, but several combinations of that kind of support sections and in each instance at least one fastening element in order to achieve an optimum integration of the circuitboard into the housing concept. By circuitboard in the sense of the invention is understood a preferab'y plate-shaped element with at least one conductor track and/or at least one active or passive electronic component.

A form of embodiment can be realised in which the fastening element is led laterally past the circuitboard or is received in a circuitboard opening open at the edge. However, it is particularly preferred if the fastening element penetrates the circuitboard at a spacing from the edge in order, as a consequence, to realise largest possible support areas at the support sections or at an insert axially received between a support section and the ci rcuitboard.

In a development it is with advantage provided that, preferably additionally to the fastening element, an axial projection penetrates one of the support sections of the circuitboard, preferably in a region radially outside the fastening element. For preference the projection is a preferably central section of the support section which projects beyond the support surface, which is especially annular, of the support section. Due to the fact that one of the support sections penetrates the circuitboard by an axial projection, the mechanical stability of the connection is enhanced, particularly when the diameter of the circuitboard opening penetrated by the axial projection corresponds with the diameter of the axial projection plus merely a minimum play. A transverse displacement of the circuitboard relative to the support sections can thereby be securely prevented.

In order to be able to apply a defined clamping force to the circuitboard a form of embodiment is preferred in which the projection in the mounted state bears directly against the opposite housing part. For preference the projection for this purpose projects in axial direction into the opposite support section and is preferably supported on an inner annular shoulder of the support section. Alternatively, a fit insert is arranged axially between the axial projection and the support section which is opposite and/or receives this. For increasing the resistance to vibration, this insert is preferably constructed as a damping insert from a resilient material.

In addition, an embodiment can be realised in which the two support sections are supported directly on the circuitboard. However, it is preferred if a fit insert, preferably a damping insert of a resilient material, is provided between one of the support sections and the circuitboard in order to increase the vibration resistance of the circuitboard arrangement. If an insert is provided between one of the support sections and the circuitboard it is possible to dispense with an insert between the axial projection and the opposite support section.

As already mentioned, an embodiment can be realised in which the fastening element goes past the circuitboard at the edge. In this case the first and second (effective) support surfaces of the first and second support sections, by which the first or second support section bears either directly against the circuitboard or a fit insert, are not circular or annular. However, for providing large support surfaces it is of advantage to provide annular or circular support surfaces at the support sections.

For realisation of a particularly economic circuitboard arrangement, which in addition has a particularly high mechanical strength, it is of advantage to construct the fastening element as a fastening screw (tightening element), wherein the fastening screw is screwed together with an internal thread of one of the support sections. In that case the internal thread can if desired be produced when the fastening screw is screwed in, in particular a self-tapping screw can be provided as fastening screw.

In order to be able to load both support sections in simple manner directly with an axial force it is provided in a development of the invention that the fastening screw is arranged to penetrate an opening of the support section which does not have an internal thread.

For preference the support section penetrated by the fastening screw is the support section penetrating the circuitboard and having an axial projection. In order to load this support section with an axial force the fastening screw is preferably supported by its screw head on a side of the support section remote from the circuitboard and thus presses the corresponding support section in the direction of the opposite support section, whereby the circuitboard is securely clamped.

In a particularly preferred form of embodiment the two housing parts which are tightened, particularly screwed, together are made of plastics material, particularly plastics material injection-moulded parts.

A preferred embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which Fig. I is a sectional view of part of a circuitboard arrangement embodying the invention.

Referring now to the drawings, Fig. 1 shows a circuitboard arrangement 20 (circuitboard fastening) which comprises a housing 30 formed by two housing parts constructed as plastics material injection-moulded parts, namely a first housing part 21 lower in the drawing and an opposite, second housing part 22 at the top in the drawing. The two housing parts 21, 22 are constructed as housing shells and comprise a first outer wall 23 and a second outer wall 24, respectively. The first outer wall 23 is formed by a planar base wall section 25 and an encircling first side wall section 26 which adjoins thereat at the edge and which extends angularly with respect to the first base wall section 25. In analogous manner, the second outer wall 24 is formed by a second base wall section 27 and a second side wall section 28 extending at an angle thereto in the direction of the first side wall section 26.

A circuitboard 29 with electrical lines (not shown) as well as electronic components (not shown) is disposed axially between the housing parts 21 and 22. The circuitboard 29 is, as will be explained later in more detail, an integral component of the concept of the housing 30 formed by the housing parts 21 and 22.

A dome-shaped first support section 31, which extends substantially perpendicularly to the first base wall section 25 in the direction of the second base wall section 27, is formed at the first outer wall 23, more specifically at the first base wall section 25, which runs substantially parallel to the second base wall section 27. The first support section 31 is shaped in its lower region as a hollow cylindrical sleeve section 32 at which an annular first support surface 33 (outer annular shoulder) is formed at the end face, the circuitboard 29 resting directly on this surface. The radial extent of the first support surface 33 corresponds, in the illustrated embodiment, at least approximately with the wall thickness of the sleeve section 32. The sleeve section 32 goes axially over into an axial projection 34, which penetrates a circuitboard opening connecting the two parallel flat sides 36 and 37 of the circuitboard 29 together. The projection 34 is constructed as a hollow cylindrical sleeve, the outer diameter of which is smaller than the outer diameter of the sleeve section 32 by twice the radial extent of the first contact surface 33. The axial projection 34 and the sleeve section 32 are arranged concentrically with respect to a notional axis 39 substantially perpendicular to the base wall sections 25, 27. The diameter of the circuitboard opening corresponds with the outer diameter of the projection 34 plus a minimum play. The projection 34 projects, on the side of the circuitboard 29 remote from the sleeve section 32, a small distance in axial direction into a dome-like second support section 38. The second support section 38 is formed at the second outer wall 24 of the section housing part 22, more specifically at the second base wall section 27, and extends substantially perpendicularly to the second base section 27 in the direction of the circuitboard 29 towards the first support section 25. The projection 34 bears by its end face against an inner annular shoulder 40 of the outer cylindrical second support section 38. Provided centrally in the second support section 38 is an internally threaded opening 41 which is arranged concentrically with the axis 39 and into which a fastening element 42, which has the form of a fastening screw, is screwed by an external thread. Formed at the end at the second support section 38 is a second annular support surface 43 by which the second support section 38 is supported indirectly on the circuitboard 29 and directly on an annular fit insert 44 of a resilient material, which in turn bears directly against the upper flat side 37of the circuitboard 29.

As can be further inferred from Fig. 1, the second support surface 43 is formed at an end annular section 48 of the second support section 38, which projects in axial direction beyond the end face of the axial projection 34, namely the end face supported at the annular shoulder 40. A step opening for reception of the axial projection 34 and the fastening element 42 arranged centrally within this is thus provided in the first support section 31.

The fastening element 42 constructed as fastening screw penetrates a central opening, which is formed as a channel, of the first support section 31. The opening is aligned along the axis 39 with the internally threaded opening 41 in which the fastening element 42 is threadedly received. The fastening element 42 bears by a screw head thereof against a face 47 of the first support section 31 remote from the circuitboard 29. The fastening element 42 thus engages not only the first support section 31 (by the screw head), but also directly against the second support section 38 (by its external thread) and tightens the support sections 31 and 38 axially in direction towards one another and thus in direction towards the circuitboard 29. The fastening element 42 thus has not only the function of direct application of a clamping force, but also that of detachably fixing the housing parts 21 and 22 to one another.

As further evident from Fig. 1, the screw head is received completely within the first support section 31 and thus does not protrude outwardly, thus does not project outwardly beyond the outer waIl 23.

Claims

CLAIMS1. A circuitboard arrangement comprising a housing, which comprises a first housing part and at least one second housing part fixed to the first housing part by means of at least one fastening element, and a circuitboard clamped between a first support section of the first housing part and a second support section of the at least one second housing part, the fastening element being arranged to engage both support sections.
2. An arrangement according to claim 1, wherein the fastening element penetrates an opening in the circuitboard.
3. An arrangement according to claim 2, wherein the opening has a closed circumference.
4. An arrangement according to claim 2 or claim 3, wherein one of the support sections has a projection penetrating the opening.
5. An arrangement according to claim 4, wherein the projection penetrates the opening radially outside the fastening element.
6. An arrangement according to claim 4 or claim 5, wherein the projection is supported directly at the other support section or at an insert disposed between the projection and the other support section.
7. An arrangement according to claim 6, wherein the insert comprises a damping element.
8. An arrangement according to any one of the preceding claims, wherein either or each of support sections is supported at the circuitboard by way of an insert disposed between the respective support section and the circuitboard.
9. An arrangement as claimed in claim 8, wherein the insert which is disposed between the respective support section and the circuitboard comprises a damping element.
10. An arrangement according to any one of the preceding claims, wherein at least one of the support sections has an annular support surface.
11. An arrangement according to any one of the preceding claims, wherein the fastening element comprises a screw threadedly engaging a thread of the first or second support section.
12. An arrangement according to claim 11, wherein the thread of the first or second support section is an internal thread.
13. An arrangement according to claim 12, wherein the screw penetrates an opening of the first or second support section.
14. An arrangement according to one of claims 11 to 13, wherein the screw is supported by a screw head at a side of the first or second support section remote from the circuitboard
15. An arrangement according to any one of the preceding claims, wherein at least one of the housing parts is made of plastics material.