FR3137318A1 - HOUSING ASSEMBLED BY DISCONTINUOUS LASER WELDING - Google Patents

Abstract

Housing (B1) comprising a bottom (2) and a cover (4) made of hot-melt material, the bottom (2) having an open end surrounded at least in part by a flange (10) and the cover (4) having an open end surrounded at least partly by a flange (18), the two flanges (10, 18) being in contact with each other. The two flanges (10, 18) are assembled by laser welding which assembles only part of the flanges, the welding being configured to ensure the desired assembly robustness. The flanges (10, 18) have sufficient width (L1, L2) so that the width of the weld ensures the desired assembly robustness. [Fig.3]

Description

HOUSING ASSEMBLED BY DISCONTINUOUS LASER WELDING TECHNICAL FIELD AND PRIOR ART

The present invention relates to a housing assembled by discontinuous laser welding and to a method of manufacturing such a housing.

In the field of braking, electromechanical actuators are increasingly used, particularly for actuating the parking brake.

For example, a drum brake includes a hydraulic actuator for service braking, and an electromechanical actuator to activate the parking brake.

An electromechanical actuator comprises an electric motor, a reduction gear and a mechanical part transforming the rotational movement of the geared motor into a spacing movement of the segments.

The electric motor is for example fixed on the exterior face of the drum brake plate.

In order to protect the motor and allow it to be fixed, the motor is housed in a plastic housing comprising a bottom and a cover. The cover has a connector to connect the motor to a power source and a control unit.

Generally the cover and the bottom are joined to each other by making a weld, preferably a weld obtained by a laser beam. The laser welding assembly process is very interesting, because it provides localized heating which limits the risk of damage to the rest of the parts.

The cover and the base each have at their open end a flange surrounding the open end. One end of the motor is housed in the bottom, the other end of the motor is covered by the cover, the two flanges being in contact with each other. Laser welding is then carried out between the two flanges. The cover material is transparent at the wavelength of the laser beam while the bottom material is absorbent at this wavelength. The laser beam passes through the cover flange and heats the bottom flange, which ensures the fusion of the areas of the two flanges in contact. The path of the laser beam is such that it closes on itself, which forms a continuous weld between the two flanges, the weld closes on itself. The assembly thus formed has a cylindrical shape.

In one configuration, the connector extends radially. This is then in the path of the laser beam. However, the connector is too thick for the laser beam to pass through without damaging it. Consequently, welding in the flange portions to the right of the connector cannot be carried out. The weld then does not close on itself and has two points of discontinuity. The assembly by laser welding is then weakened.

It is therefore an aim of the present invention to provide a housing made of plastic material comprising a bottom and a cover having a robust assembly.

The aim stated above is achieved by a housing comprising a bottom and a cover made of hot-melt material, the bottom comprising an open end surrounded at least partly by a flange and the cover comprising an open end surrounded at least partly by a flange , the two flanges being in contact with each other, in which the two flanges are assembled by laser welding which assemble only part of the flanges, the welding being configured to ensure the robustness of the desired assembly.

For example, the cover includes an element extending radially outwards and preventing a closed weld from being made on all the flanges.

In an exemplary embodiment, the laser weld bead offers sufficient width, which makes it possible to compensate for the absence of a weld closing on itself.

In another embodiment, the path of the weld forms a continuous loop without completely surrounding the axis of the housing, so that the weld does not present any discontinuity or sudden interruption which tends to weaken the assembly.

Very advantageously, the flanges are shaped to provide areas allowing the laser beam to make a half-turn while remaining in contact with the flanges, which makes it possible to generate a robust weld bead.

Preferably, the housing and the cover define between them a housing for tightening a seal making it possible to produce a watertight assembly.

In other words, the inventors thought of adapting the assembly by laser welding so that it produces a sufficiently robust assembly, while other means of assembly could have been considered.

Thanks to the invention, the architecture of the case which is very compact is very little impacted.

The present invention then relates to a housing comprising a bottom and a cover made of hot-melt material, the bottom comprising an open end surrounded at least partly by a flange and the cover comprising an open end surrounded at least partly by a flange, the two flanges being in contact with each other, in which the two flanges are assembled by a laser weld which assembles only part of the flanges, the weld being configured to ensure the desired assembly robustness.

In an exemplary embodiment, the flanges have sufficient widths so that the width of the weld ensures the desired assembly robustness.

Preferably, the minimum width of the flanges is 2.5 mm.

Preferably, the weld is configured to offer tensile strength greater than 500 N and/or vibration strength greater than 150g.

In another embodiment, each flange comprises a first angular end and a second angular end, the two first angular ends being in contact and the two second angular ends being in contact, at least the first angular end of each flange having a width in the radial direction sufficient so that the laser weld formed during assembly has in the first ends the shape of a loop connecting a forward path of a laser beam and a return path of the laser beam.

Very advantageously, the second angular ends of each flange have a width in the radial direction sufficient for the laser weld formed during assembly to have in the second angular ends the shape of a loop connecting a forward path of the laser beam and a return path of the laser beam.

According to an additional characteristic, one of the flanges has a groove configured to receive a part of the other flange, and in which the weld assembly is in the bottom of the groove. Advantageously one of the flanges is bordered internally by a groove and the other of the flanges is bordered internally by a sleeve, the sleeve penetrating into the groove, and in which sealing means are clamped between a bottom of the groove and the muff.

In an advantageous example, the bottom and the cover are made of polybutylene terephthalate reinforced with fiberglass, for example at 30% (PBT GF 30).

Another object of the present invention is an electric actuator comprising a housing according to the invention and a geared motor housed in the housing.

In an exemplary embodiment, the cover comprises an element extending radially outwards, housing an electrical connector for the geared motor.

Another object of the present invention is a method of manufacturing a housing according to the invention, comprising:
a) Supply of a base and a cover according to the invention,
b) Bringing the flanges into contact so that said first angular ends are in contact with each other,
c) Activation of the laser beam so that it targets one of the flanges,
d) Movement of the beam in a first direction towards said first angular ends,
e) After reaching said ends, movement of the laser beam in a second direction opposite to the first direction, the change in direction of movement being obtained by performing a loop-shaped reversal at said first ends.

In step b), a bottom and a cover according to the invention are provided, and in step e), the laser beam changes direction in the second ends of each flange by performing a loop-shaped reversal at the level of said second ends.

In an advantageous example, the laser beam makes several paths between the first and second ends, the paths being at least partly merged or at least partly distinct.

The manufacturing process may include a step between step a) and step b) of installing a geared motor at the bottom.

BRIEF DESCRIPTION OF THE FIGURES

The following description will be better understood with the help of the appended drawings in which:

is a perspective view of an example of a housing according to the invention,

is a view of one end of the housing of the ,

is a partial longitudinal sectional view of a first mode of assembling the housing of the ,

is a side view of an alternative embodiment of the housing of the ,

is a top view of a housing according to a second assembly mode,

is a bottom view of the housing cover of the ,

is a bottom view of a cover of a housing according to a variant of the assembly mode of the ,

is a bottom view of a cover according to another embodiment of the second assembly mode,

is a bottom view of a cover according to another embodiment of the second assembly mode.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention will be described in detail in the context of an electric actuator housing for a brake. But it will be understood that the invention applies to the assembly of any housing made of hot-melt material.

In Figures 1 and 2, we can see an embodiment of an example of a housing according to the invention. Box B1 is configured to house an electric motor (not visible). The housing B has a shape of revolution of axis

The cover 4 comprises a body 12 provided with an open longitudinal end 14. The body 12 also comprises a radially projecting element 16 and forming a connector making it possible to connect the electric motor to a source of energy and to a control unit ( not shown).

The body 12 also includes a flange 18 partially surrounding the open end 14. In particular the flange 18 is interrupted in line with the projecting element 16. Thus an angular zone α around the open end 14 does not include a flange. The angle α is less than 180°.

A housing in which the cover flange is not interrupted does not depart from the scope of the present invention.

The fact that the bottom flange 10 is continuous and completely surrounds the body has the advantage of not having to orient the bottom in relation to the cover. However, as a variant, the bottom flange is interrupted on an angular sector which is superimposed on the angular sector α.

The angular sector α is such that a larger portion of the flange 10 will be melted by laser irradiation to avoid any creation of a mechanical stop between the flange 10 and 18. The melted portion of the flange 10 is an angular sector of (360 - α + safety margin of a few degrees).

As can be seen on the , the flange 18 has two free ends 18.1, 18.2 which potentially form weakening zones.

On the , we can see a partial longitudinal sectional view of a mode of assembly of the housing of Figures 1 and 2.

In this example, the flange 10 comprises an annular assembly face 20 and an annular groove 22 located radially inside the assembly face 20, and concentric with the assembly face.

The flange 18 comprises an annular assembly face 24 located in the bottom of an annular groove 26 and an annular sleeve 28 extending longitudinally and located radially inside the groove 26 and penetrating into the groove 22.

The assembly face 24 does not close around the axis X due to the missing annular zone α. The assembly face 24 has the shape of an arc of a circle extending over an angle of 360°- α.

The lid material and/or the housing material is hot melt.

At least the material of the flange 18 of the cover is transparent to the wavelength of the laser beam used for welding, so when the laser beam passes, the bottom flange 10 is heated, causing local melting of the flange 10 and flange 18.

Preferably, the same material is used for the manufacture of the cover and the housing. These are preferably polymer materials.

According to one example, the cover and the housing are made of poly(butylene terephthalate)(PBT)

According to another example, the cover and the housing are made of polyamide 6 (PA6).

According to another example, the cover and the housing are made of polypropylene.

According to another preferred example, the cover and the housing are made of polybutylene terephthalate reinforced with fiberglass, for example at 30% (PBT GF 30).

The weld extends over an arc extending over an angle of the order of 360°- α between the ends 24.1, 24.2 of the assembly surface 24.

The groove 22 is continuous and closes around the axis X, it then advantageously allows sealing means 30 to be accommodated between the cover and the bottom.

For example, the sealing means 30 comprise a silicone seal or a liquid seal also designated FIPG (Form In Place Gasket in Anglo-Saxon terminology) which is polymerizable in an ambient environment or under temperature. The seal is placed in the liquid state in the groove, the annular sleeve 28 is put in place in order to make the seal flow, then the seal is polymerized. Alternatively, the sealing means comprise an O-ring type seal or CIPG (Cured In Place Gasket in Saxon terminology) crushed between the bottom of the groove 22 and the free end of the annular sleeve 28.

In this exemplary embodiment, the assembly faces 20, 24 have a width considered in a radial direction sufficient to ensure connection of the cover and the bottom, despite the fact that the weld has a discontinuity. 4.

Preferably, the width of the weld is such that it provides tensile strength greater than 500 N.

Preferably, the width of the weld is such that it offers vibration resistance greater than 150g.

The assembly face 20 advantageously has a width L1 of less than 3 mm, and preferably the width L1 is of the order of 2.5 mm.

In a preferred example, the assembly face 24 has a width L2 of the order of 3.7 mm. The dimensions of the assembly faces depend in particular on the depth of the weld.

It is therefore possible to produce a weld with a large width of around 2.5 mm. In comparison, state-of-the-art laser welding is of the order of 1 mm to 1.5 mm.

Preferably, the diameter of the housing is such that the total length of the weld bead is less than 300 mm

On the , we can see a variant of the housing of the , in which the flanges 10' and 18' completely surround the open ends of the cover and the bottom.

The manufacturing process of the actuator of the is for example the following:
- Supply of bottom 2 and cover 4.
- Mounting the gear motor in the bottom.
- The cover is placed on the bottom so that their flanges 10, 18 are in contact with each other.
- The laser beam is placed on the cover side and aims at the first end 24.1 of the assembly surface 24. The laser is moved on the flange 18 towards the second end 24.2 and up to the end 24.2. In one example, the laser beam makes a single trip from end 24.1 to end 24.2 and in another example, the laser beam makes at least one round trip in order to reach the desired weld width.

On the , we can see a top view of another example of B2 housing according to the invention. On the , you can see the cover of the housing of the .

The cover 104 comprises a flange 118 partially surrounding the body of the cover and comprising two angular ends 118.1, 118.2 shaped so as to allow the laser beam to turn around when it reaches one or the other of the angular ends, thus avoiding to generate a discontinuity in the weld which can be damaging to the robustness of the assembly.

Preferably, the weld according to this configuration is such that it offers a tensile strength greater than 500 N.

Preferably, the welding according to this configuration is such that it offers vibration resistance greater than 150g.

The ends 118.1 and 118.2 each have substantially the shape of an ear.

The flange 118 includes a groove 126, the bottom of which forms the assembly face 124 which defines the path of movement of the laser beam. The groove 126 includes, at the two ends 118.1 and 118.2, a loop which allows the laser beam to produce a closed weld. The curls have an elongated shape. This achievement has the advantage of offering a smaller radial footprint.

The path of the laser beam in the groove 126 is symbolized by the broken line.

The bottom includes a flange comprising an assembly face of complementary shape to the assembly face 124.

In a variant, the flange 218 of the cover and/or the bottom flange are flat and do not physically delimit the path of the laser, as is shown schematically on the .

On the , we can see a variant embodiment of a cover in which the flange 318 has looping ends 318.1, 118.2 of the assembly face 324 having a circular shape.

Alternatively, the flange of the cover has a single end allowing the laser to perform a reversal without generating a discontinuity, which has the effect of improving the robustness of the assembly compared to an assembly comprising two discontinuities.

In the example described and advantageously, the outward path of the laser beam and the return path are partly common. Alternatively, the outward and return paths are completely distinct (shown in broken lines) as is visible on the flange 418 shown on the .

This second method of assembly has the advantage of not requiring a wider weld than that of the state of the art. However, a housing according to the second assembly method having a weld wider than that of the state of the art, for example of the order of 2.5 mm, does not go beyond the scope of the present application.

An example of a housing manufacturing process according to the second assembly mode will now be described.

The process includes:
- Supply of bottom 102 and cover 104.
- Mounting the gear motor in the bottom 102.
- Placement of the cover on the bottom so that their flanges 110, 118 are in contact with each other.
- The laser beam is placed on the side of the cover and aims at the first ear 118.1 and moves on the flange towards the second ear 118.2. When the laser beam reaches the second ear 118.2, it makes a half-turn, forming a loop and leaves again in the direction of the first ear 118.1, until it reaches the starting point of the weld; the laser beam can make several passes between the two ears. The weld thus produced has no discontinuity.

The invention makes it possible to preserve the assembly by means of laser welding which ensures localized heating, which has the effect of putting less stress on the components during the welding stage.

In the example shown, the housing has a substantially circular cross section. It will be understood that the invention applies to housings of any section, for example of an elliptical section, of a polygonal section, for example rectangular.

Furthermore in the description above, the cover has a radial extension which prevents welding over the entire contour of the flanges. But it will be understood that a cover having another shape does not go beyond the scope of this application.

The present invention applies to any type of plastic material housing assembled by laser welding, more particularly to housings housing electric actuators, and even more particularly brake actuators.

Claims (15)

Housing comprising a bottom and a cover made of hot-melt material, the bottom (2) comprising an open end surrounded at least partly by a flange (10, 110) and the cover (4) comprising an open end surrounded at least partly by a flange (18, 118), the two flanges (10, 110, 18, 118) being in contact with each other, in which the two flanges (10, 110, 18, 118) are assembled by laser welding which assembles only part of the flanges (10, 110, 18, 118), the weld being configured to ensure the desired assembly robustness. Housing according to claim 1, in which the flanges (10,18) have widths (L2, L3) sufficient for the width of the weld to ensure the desired assembly robustness. Housing according to claim 2, in which the minimum width of the flanges is 2.5 mm. Housing according to claim 1, 2 or 3, in which the welding is configured to offer a tensile strength greater than 500 N and/or a vibration resistance greater than 150g. Housing according to one of claims 1 to 4, in which each flange (110, 118) has a first angular end and a second angular end, the two first angular ends being in contact and the two second angular ends being in contact, at minus the first angular end of each flange (110, 118) having a width in the radial direction sufficient for the laser weld formed during assembly to have in the first ends the shape of a loop connecting a forward path of a laser beam and a return path of the laser beam. Housing according to claim 5, in which the second angular ends of each flange (110, 118) have a width in the radial direction sufficient for the laser weld formed during assembly to have in the second angular ends the shape of a loop connecting a forward path of the laser beam and a return path of the laser beam. Housing according to one of the preceding claims, in which one (18) of the flanges comprises a groove (26) configured to receive part of the other flange (10), and in which the weld assembly is in the bottom of the throat (26). Housing according to one of the preceding claims, in which one (10) of the flanges is bordered internally by a groove (22) and the other of the flanges is bordered internally by a sleeve (28), the sleeve (28) penetrating in the groove (22), and in which sealing means (30) are clamped between a bottom of the groove (22) and the sleeve (28). Housing according to one of the preceding claims, in which the bottom and the cover are made of polybutylene terephthalate reinforced with fiberglass, for example at 30% (PBT GF 30). Electric actuator comprising a housing according to one of the preceding claims and a geared motor housed in the housing. Electric actuator according to the preceding claim, in which the cover comprises an element extending radially outwards, housing an electrical connector for the gear motor. Method of manufacturing a housing according to claim 5, comprising
a) Supply of a base and a lid,
b) Placed in contact with the flanges so that said first angular ends are in contact with each other,
c) Activation of the laser beam so that it targets one of the flanges,
d) Movement of the beam in a first direction towards said first angular ends,
e) After reaching said ends, movement of the laser beam in a second direction opposite to the first direction, the change in direction of movement being obtained by performing a loop-shaped reversal at said first ends. Method of manufacturing a housing according to claim 6, comprising
a) Supply of a base and a lid,
b) Bringing the flanges into contact so that said first angular ends are in contact with each other,
c) Activation of the laser beam so that it targets one of the flanges,
d) Movement of the beam in a first direction towards said first angular ends,
e) After reaching said first ends, moving the laser beam in a second direction opposite to the first direction, the change in direction of movement being obtained by performing a loop-shaped reversal at said first ends, and the laser beam changing of direction in the second ends of each flange by performing a loop-shaped reversal at said second ends. Manufacturing method according to the preceding claim, in which the laser beam makes several paths between the first and second ends, the paths being at least partly merged or at least partly distinct. Manufacturing method according to one of claims 12 to 14, comprising a step between step a) and step b) of placing a gear motor in the bottom.