EP1297592A1

EP1297592A1 - Electrical device

Info

Publication number: EP1297592A1
Application number: EP01943160A
Authority: EP
Inventors: Herbert Gentner; Erwin Liegl; Ralf Haug
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-06-02
Filing date: 2001-05-26
Publication date: 2003-04-02
Also published as: KR20020021170A; CN1381081A; DE10027363A1; JP2003535479A; DE10027363B4; US20020173199A1; US6652312B2; WO2001093377A1

Abstract

The invention relates to an electrical device comprising two housing parts, which can be joined to form a closed housing and which enclose a housing interior space when joined. Said electrical device also comprises an electric/electronic circuit element, which is arranged inside the housing interior space, and a sealing material for protecting the circuit element. According to the invention, both housing parts are provided in the shape of half-shells and the inner area of the half-shells is subdivided by inner walls into at least two chambers, of which a first chamber is filled with the sealing material and has spatial dimensions that are larger than those of the circuit element. When the half-shells are assembled, the inner walls of the second half-shell overlap the inner walls of the first half-shell in an interspaced manner, and the inner walls of the first half-shell slightly project into the first chamber of the second half-shell. Between both half-shells, the circuit element is enclosed up to the electrical connections thereof by the sealing material, which is contained in both first chambers.

Description

Electric device

State of the art

The invention relates to an electrical device with the features mentioned in the preamble of claim 1.

From EP 0722 624 B1 an electrical device is known which comprises a first and a second housing part which, together with the first housing part, forms a closed housing. A circuit part designed as a printed circuit board is arranged in the housing, support elements formed on the first housing part reaching through openings in the printed circuit board. The support elements are designed in such a way that the printed circuit board moves in the direction of the first housing part when the second housing part is placed on it, and a sealing material arranged between the printed circuit board and the first housing part is brought under compression and displaced into a position in which it rests on the side walls of the housing Housing forms a circumferential bead and thereby seals the contact area of the two housing parts. In the housing part sealed in this way, an air-filled cavity remains between the printed circuit board and the second housing part. Securing elements, which are formed on the second housing part, prevent the printed circuit board in its end position, once reached, from being pushed back into the cavity by the compressive force of the compressed sealing material, as a result of which the sealing bead would be pulled off the housing walls. A disadvantage of the known device is that the circuit board with openings for the support elements elements must be provided and thus space for the arrangement of electrical and / or electronic components on the circuit board is lost. In addition, electrical connection lines cannot be routed through the bead-like seal between the housing parts into the interior of the housing and must therefore be routed in a complex manner through a separate passage in one of the two housing parts into the interior of the housing. This passage must also be sealed, which requires increased effort. Harmful gases in the enclosed cavity above the circuit board can impair the functioning of electronic components on the circuit board.

Advantages of the invention

The electrical device according to the invention with the features of claim 1 avoids the disadvantages occurring in the prior art and enables reliable protection against harmful environmental influences for a circuit part arranged in a housing. The device ensures that the circuit part is adequately sealed against splash water, moisture or when immersed in water. The device is both simple and inexpensive to manufacture and has two half-shells, the interior of which is divided by inner walls into at least two chambers, of which a first chamber is filled with sealing material, preferably a gel, and has spatial dimensions that are larger than the dimensions of the circuit part. In the assembled state of the two half-shells, the inner walls of the second half-shell overlap the inner walls of the first half-shell at a distance, as a result of which the sealing material contained in the two half-shells comes into contact in a frame-like, circumferential area around the circuit part. det and the circuit part seals all around. Due to tolerances of the housing dimensions, tolerances when filling the sealing material and a shrinking process when the sealing material hardens, the sealing material filled into the first chambers forms a meniscus before the two half-shells are joined together, so that the surface of the sealing material is concavely curved in both chambers and lies against the upper edges of the inner walls, but is set back slightly in the center of the chamber. This cannot easily be avoided and, without countermeasures, leads to the fact that when the two half-shells are joined together, cavities form above or below the circuit board due to the concave curvature. In order to prevent an insufficient displacement of the sealing material in the edge region of the printed circuit board resulting from the presence of the cavities, when the two half-shells are joined together, leads to inadequate sealing of the edge region

When the two half-shells are joined together, the inner walls of the first half-shell penetrate a little into the first chamber of the second half-shell. This ensures that the interlocking first chambers of the half-shells form an overlap area, a sufficient amount of sealing material being displaced from the overlap area when the half-shells are joined together in order to surround the edge area of the circuit part with sealing material with sufficient reliability. In this way it is advantageously achieved that the circuit part between the two

Half shells through the sealing material contained in the first two chambers is encased in sealing material except for its electrical connections, or is arranged encapsulated in the sealing material.

Advantageous refinements and developments of the invention are made possible by the features contained in the subclaims.

The inner area of each half-shell is advantageous due to two inner walls running parallel to each other, which two connect the other opposite side walls of the half-shells to one another, divided into a centrally arranged first chamber and two second chambers which laterally adjoin the first chamber. The second chambers provided in each half-shell serve, inter alia, as receiving areas for excess sealing material which is displaced from the first chambers when the two half-shells are joined together. The distance between the inner walls of the first and second half-shells forms an outflow channel for sealing material displaced from the first chambers, which can escape into the second chambers via the outflow channel.

The half-shells can advantageously be connected to one another via latching means. When the two half-shells are joined together, larger amounts of sealing material are compressed and displaced from the overlap area of the first chambers. Without connecting means, the strong compressive forces resulting from the compression would push the two half-shells apart again. The locking means must therefore be able to withstand greater forces. It is therefore advantageous if the latching means comprise latching hooks arranged on a half-shell with barb-shaped latching lugs, which each engage in a guide slot arranged on the other half-shell and, with their latching lugs, each engage behind a projection arranged in the guide slot in a barb-like manner. The guide slots protect the locking hooks, so that accidental unlocking of the locking lugs is not possible. In particular, the width of each guide slot and the geometrical dimensions of the assigned latching lug can be coordinated with one another in such a way that a latching lug engaging behind the projection in a barb-like manner cannot be released again from its latching position without being destroyed.

The side walls of the half-shells advantageously have recesses which, when the housing is assembled, partially form openings arranged between the two half-shells for the passage of electrical connecting lines. When the two half-shells are joined together, the connecting lines led through the openings to the outside are embedded in the sealing material.

It is also advantageous to provide strain relief for the electrical connecting lines on at least one half-shell.

drawings

An embodiment of the invention is illustrated in the drawings and explained in the following description. It shows

1 shows a cross section through an electrical device according to the invention,

2 shows an enlarged detail from FIG. 1, FIG. 3 shows the second half-shell in a perspective view, FIG. 4 shows the first half-shell in a perspective view, FIG. 5 shows a top view of the first half-shell without the second half-shell with one placed on the sealing material Circuit part and a film conductor connected to it.

Description of an embodiment

1 shows an electrical device for a system for occupant classification in a motor vehicle. The device comprises a housing 1 in which an electronic circuit part 4, for example a printed circuit board with electrical and / or electronic components 7, 8 arranged thereon, is arranged. The circuit board is via a foil conductor track 6 connected to a seat mat, not shown, for a vehicle seat, which has several local pressure-sensitive sensors. Furthermore, a cable 5 is provided that connects the electronic circuit arranged on the circuit board with an airbag. The device makes it possible to determine the occupancy of a vehicle seat and the type of person (child or adult) and to control an airbag depending on the data determined in this way. In principle, however, the invention is not limited to the exemplary embodiment shown here, but can also be used in other electrical devices which use a circuit part arranged in the interior of a housing and which is to be protected against environmental influences, such as moisture or harmful gases.

As shown in FIG. 1, the housing 1 comprises a first half-shell 2 and a second half-shell 3. Both are made of plastic and, when assembled, contain a housing interior in which the printed circuit board 4 is arranged. The half-shells can also be made of another suitable material, for example metal. FIG. 4 shows a perspective illustration of the inner region of the first half shell, and FIG. 3 shows a representation of the inner region of the second half shell. As can be seen in FIG. 4, the first half shell 2 comprises four side walls 21, 22, 23, 24 and a bottom wall, on the inside of which a grid of webs 41 is formed. The opposite side walls 22 and 24 are connected to one another by two inner walls 25, 26 which run parallel to one another and which divide the inner region of the first half-shell 2 into a first chamber 20 and two second chambers 27a and 27b adjoining it laterally. The essentially rectangular first chamber 20 is delimited by the side walls 22 and 24 and the inner walls 25 and 26. Furthermore, the side wall 23 has a U-shaped recess 29 and the side wall 21 has a C-shaped recess 28. On each of the two side walls 23, two latching hooks 44 are formed which protrude parallel to the side walls 21, 23 from the upper edge of the side walls. In the second chamber 27b arranged adjacent to the recess 29, two pins 42 and 43 protrude from the bottom of the first half-shell 2 into the inner region, which serve as strain relief for a foil conductor track 6. Furthermore, the outer edge of the side walls 31, 32, 33, 34 has a partially circumferential rib 60.

The second half-shell 3 is shown in FIG. 3 and is constructed similarly to the first half-shell 2. It has four side walls 31, 32, 33, 34 and a bottom wall, on the inside of which webs 51 are arranged in a lattice shape. The side walls 32 and 34 are connected to one another via two inner walls 35 and 36 running parallel to one another. The side walls 32 and 34 and the inner walls 35 and 36 delimit a centrally arranged first chamber 30, which is separated by the inner walls 35 and 36 from two laterally adjoining second chambers 37a and 37b. The side wall 33 has a U-shaped recess 39 and the side wall 31 has an egg-shaped recess 38. In addition, four continuous guide slots 54 with a rectangular cross section for the latching hooks 44 of the first half-shell 2 are embedded in the side walls 31 and 33. The guide slots 54 extend parallel to the side walls 31, 33 and each have an opening 57, 58 at their ends (FIG. 2). The outer edge of the side walls 21, 22, 23, 24 is provided with a partially circumferential groove 61, into which the rib 60 of the second half shell 3 engages when the two half shells are joined together.

The length and width of the first chamber 20 of the first half-shell 2 and the length and width of the first chamber 30 of the second half-shell 3 are each larger than the length and width of the printed circuit board 4. The distance between the inner walls 35 and 36 of the second half-shell 3 is larger than the distance between the inner walls 25 and 26 of the first half shell 2. In the manufacture of the device, the first two chambers 20 and 30 are filled with a flowable sealing material, not shown in FIGS. 3 and 4, approximately up to the upper edge of the delimiting inner walls and side walls. The highly viscous sealing material consists, for example, of a hardened gel. The gel can have a composition as shown in EP 0 722 624 B1. The gel filled into the chambers 20, 30 forms a concavely curved surface which is set back inwards in the central area of the first chambers to the chamber floor. Subsequently, as shown in FIG. 5, a printed circuit board 4, which is provided with electrical and / or electronic components 7, 8, is placed on the gel filling 12 of the first chamber 29 of the first half-shell. The circuit board 4 is connected to a film conductor 6 of the seat mat. The film conductor 6 has two layers of mutually insulated contact strips 6a and 6b, which are separated in the end region and are connected to corresponding contact surfaces on the top and bottom of the printed circuit board 4, as can best be seen in FIG. 2. As further shown in FIG. 5, cable wires 15 of a connecting cable 5 for controlling an airbag are electrically connected to a connector 8 on the printed circuit board 4. The cable cores 15 can be arranged in the second chamber 27a of the first half shell. The film conductor 6 has circular recesses through which the pins 42 and 43 extend, whereby a strain relief for the film conductor 6 is formed. As can be clearly seen in FIG. 5, the edge of the printed circuit board 4 is separated from the side walls 24 and 22 by a distance b and a few millimeters from the inner walls 25 and 26 by a distance a.

Then the second half-shell 3 is placed on the first half-shell 2. The four locking hooks 44 engage a first half-shell 2 through the openings 57 into the guide slots 54 of the second half-shell 3, as can best be seen in FIG. 2. Since the distance between the inner walls 35 and 36 of the second half-shell 3 is larger than the distance between the inner walls 25 and 26 of the first half-shell 2, the inner walls 35 and 36 of the second half-shell 3 overlap the inner walls 25 and 26 of the first half-shell 2 with a Distance d. When the two half-shells 2, 3 come closer together, the gel layers 12 and 13 come into contact in the first two chambers 20 and 30 in the edge region of the printed circuit board 4. By further pressing it is achieved that the inner walls 25, 26 of the first half-shell penetrate a part c into the first chamber 30 of the second half-shell 3. The inner walls 25, 26 of the first half-shell preferably penetrate a few millimeters into the first chamber 30 of the second half-shell 3. The circuit board 4 is pressed into the gel layer 13 of the second half-shell 3. The gel layers 12 and 13 are compressed and gel is displaced from the overlap area. The displaced gel is pressed partially between the spaced inner walls 25 and 35 and the spaced inner walls 26 and 36 into the second chambers 27a and 27b of the first half-shell 2. Enough gel can be displaced by the partial penetration of the first chamber 20 of the first half-shell 2 filled with gel 12 into the first chamber 30 of the second half-shell 3 filled with gel 13 to ensure with sufficient reliability that the printed circuit board with its electrical connecting lines is completely included Gel is encased or encapsulated in gel. The amount of gel displaced can be set using parameters a, b and c.

When the two half-shells 2, 3 are joined together, the egg-shaped recesses 28, 38 form a circular opening for the passage of the connecting cable 5. The wires 15 of the connecting cable 5 are in contact with the connector 8 through the gap between the inner walls 25 and 35 and are completely from gel surround. In the assembled state of the two half-shells 2, 3, the U-shaped recesses 29, 39 of the two half-shells 2, 3 form a slot-shaped opening through which the foil conductor track 6 is guided into the second chambers 27b, 37b. From there, the film conductor 6 reaches the circuit board 4 through the gap between the inner walls 26 and 36 and is encased on all sides by the gel present there.

The latching hooks 44 inserted into the openings 57 slide along the guide slots 54 when the half-shells 2, 3 are joined together, spring back behind the projections 55 in the guide slots and finally latch with their latching lugs 45 like barbs behind the projections 55, as shown in FIG. 2 is shown. The width e of the guide slots 54 is in each case dimensioned such that the associated catch 45 can just be passed between the projection 55 projecting into the guide slot and the inner wall of the guide slot opposite the projection. It can advantageously be provided that the wall 59 of the guide slot 54 provided with the projection 55 is elastically bent and springs back as soon as the latch 45 passes the projection 55. This advantageously means that the latching hooks 44 cannot be released from their latched position without being destroyed. The snap connections shown enable a very reliable and stable snap connection of the two half-shells 2, 3.

The invention is not restricted to the exemplary embodiment shown here. It is understood that modifications to the structure of the housing are possible. For example, the inner walls do not necessarily have to run parallel to one another. For example, it is conceivable to delimit the first chamber in each half-shell by, for example, circular inner walls from an annular second chamber surrounding the first chamber or similar modifications, it being important to ensure that the inner walls of the second half-shell have the Reach over the inner walls of the first half-shell at a distance and penetrate the inner walls of the first half-shell a bit into the first chamber of the second half-shell. Furthermore, exemplary embodiments are of course also conceivable, in which a further connecting cable is used instead of the foil conductor track, or a control device with only one connecting cable. Instead of the gel, another suitable flowable sealing material can be used that is partially displaced when the two half-shells are pressed together.

Claims

Expectations

1. Electrical device, comprising two housing parts (2, 3) which can be connected to form a closed housing (1) and which, when connected, enclose a housing interior, an electrical / electronic component arranged in the housing interior

Circuit part (4) and a sealing material (12, 13) for protecting the circuit part (4), characterized in that the two housing parts (2, 3) are designed as half shells and the inner region of the half shells (2, 3) is inner walls (25,26,35,36) in at least two chambers (20,27a,

27b, 30, 37a, 37b), of which a first chamber (20, 30) is filled with the sealing material (12, 13) and has spatial dimensions that are larger than the dimensions of the circuit part (4), in the assembled state of the two half-shells (2, 3) the inner walls (35, 36) of the second half-shell (3) overlap the inner walls (25, 26) of the first half-shell (2) at a distance (d) and the inner walls ( 25, 26) of the first half-shell (2) protrude a little into the first chamber (30) of the second half-shell (3) and the switching part (4) between the two half-shells (2, 3) through the in the two first chambers ( 20.30) contained sealing material (12.13) except for its electrical connections (6.15) is encased by sealing material.

2. Electrical device according to claim 1, characterized in that the inner region of the half-shells (2, 3) in each case by two parallel inner walls (25, 26, 35, 36) which have two mutually opposite side walls (22, 24, 32, 34) of the half shells in a centrally arranged first chamber (20, 30) and two second chambers (27a, 27b, 37a, 37b) adjoining the first chamber laterally.

3. Electrical device according to claim 1 or 2, character- ized in that in each half-shell (2,3) at least a second chamber (27a, 27b, 37a, 37b) as receiving areas for excess, when joining the two half-shells from the first Displaced sealing material is provided in chambers (20, 30), a drainage channel for displacement displaced from the first chambers (20, 30) by the distance (d) between the inner walls (25, 26, 35, 36) of the first and second half-shells Sealing material is formed.

4. Electrical device according to claim 1, characterized in that the half-shells (2, 3) can be connected to one another via latching means (44, 54).

5. Electrical device according to claim 4, characterized in that the latching means on a half-shell (2) arranged latching hooks (44) which each engage in a guide slot arranged on the other half-shell (54) and with their latching lugs (45) each in the guide slot (54) arranged protrusion (55) engage behind like a barb.

6. Electrical device according to claim 5, characterized in that the width (e) of each guide slot and the geometric dimensions of the associated latching lug (45) are coordinated with one another in such a way that a latching lug engaging behind the projection (55) in a barb-like manner ( 45) cannot be released from their rest position without being destroyed.

7. Electrical device according to claim 1, characterized in that the side walls (21,31,23,33) of the half-shells (2,3) have recesses (28,38,29,39) which in the assembled state of the housing part (1st ) between the two Form half shells arranged openings for the passage of electrical connecting lines (5,6).

8. Electrical device according to claim 1, characterized in that a strain relief (42, 43) for the electrical connecting lines (6) is provided on at least one half-shell (3, 4).

9. Electrical device according to one of the preceding claims, characterized in that the electrical connecting lines comprise an elastically flexible film conductor track (6).

10. Electrical device according to claim 1, characterized in that a gel is used as sealing material.