NOISE-REDUCING COMPONENT ON THE HOUSING OF AN ELECTRIC MOTOR

Description

[0001] The invention relates to vehicle braking devices.

[0002] There are two types of vehicle braking systems. In a disc braking system, a disc attached to a vehicle wheel is surrounded by two brake pads. When the user presses the brake pedal, the pads move closer to the respective faces of the disc by actuating a piston to exert pressure on them in order to slow the rotation of the disc, and therefore that of the wheel. In a drum braking system, shoes located on either side of a wheel axle move apart from each other in order to exert pressure on the internal circumferential part of a drum rotating with the wheel. These systems are also used for manual braking ("handbrake"), or emergency braking.

[0003] In all cases, and in all vehicle braking devices, braking requires actuation. This can be mechanical, but also electrical, or assisted by electrical means. The invention relates to the last two cases, that is to say when braking requires the intervention of an electric motor.

[0004] To limit magnetic losses and increase the thickness of the electric motor casing of the braking device, a slotted sheet metal is added around the casing. Without this, magnetic losses can cause disturbances, particularly in other elements of the braking device.

[0005] However, when the brake is activated, the electric brake motor generates vibrations that create noise. These vibrations are transmitted to the metal insert, which in turn generates additional noise. However, this noise can be annoying for the driver and can cause concern about the reliability of their vehicle's braking.

[0006] Documents DE102005044665, DE4306588, FR2872196, JPS59178931, JP2005124321 and JP2008006122 disclose devices for reducing noise reported around electric motors.

[0007] One aim of the invention is to reduce the noise of the vehicle's electric braking device.

[0008] For this purpose, the invention provides a member for an electric motor, comprising the characteristics defined in claim 1.

[0009] Also provided according to the invention is an electric motor comprising the characteristics defined in claim 2.

[0010] Thus, the outer sheet is not placed against the casing. The space between the casing and the outer sheet helps to dampen the vibrations of the motor, and the noise generated is therefore reduced. In addition, the outer sheet continues to fulfill its function of limiting magnetic losses. Thus, the invention makes it possible to restrict the magnetic field while reducing the noise emitted by the motor.

[0011] The body consists of two separate sheets. This "sandwich" or "three-layer" arrangement helps to absorb engine vibrations even better and reduce the noise it emits when operating.

[0012] The inner and outer sheets are separated by the material layer, with the material layer in contact with the inner and outer sheets.

[0013] Thus, the arrangement comprises three layers: a sheet metal in contact with the carcass, a layer of material, and a new sheet metal forming the external wall of the component. This arrangement allows for considerable vibration damping while continuing to limit magnetic losses. In addition, the total thickness of the component can be similar to that of a conventional component attached to the usual carcass, which does not reduce noise.

[0014] The organ wall includes a slit running from one end of the wall to the other.

[0015] Thus, the organ is open, so that it can adapt to the size of the engine casing to a certain extent via a relatively elastic mounting.

[0016] Preferably, the layer of material comprises a viscoelastic material.

[0017] This way, vibrations are better absorbed.

[0018] Advantageously, the layer of material comprises an elastomeric material.

[0019] Elastomers are indeed well suited to absorbing vibrations.

[0020] Alternatively, the material layer comprises a plastic material.

[0021] In one embodiment, this layer is loaded with ferromagnetic particles to conduct magnetic fields from the motor.

[0022] Preferably, the sheet(s) comprise electrical steel. They may also comprise soft iron.

[0023] The invention also provides an electric vehicle braking device, comprising a motor as stated above.

[0024] We will now present embodiments of the invention with the support of the appended figures, which are provided as examples and are not limiting in nature, in which: there figure 1is a perspective view of an electric motor according to a first embodiment of the invention; the figure 2 is an exploded perspective view of the engine of the figure 1 ; there figure 3 is an exploded perspective view of part of the engine of the preceding figures; the figure 4 is an axial sectional view of the engine of the preceding figures; the Figure 5 is a diagram representing the invention according to the first embodiment, and the figures 6 to 8 are diagrams according to second, third and fourth embodiments respectively, not representing the invention.

[0025] THE figures 1 to 4 illustrate an electric motor 10 for an electric vehicle braking device according to a first embodiment of the invention.

[0026] It has an outer casing 17, an end cover 11, stator elements S and rotor elements R.

[0027] The stator S comprises a pin 14 and two magnets 15 in the form of semi-cylinders of revolution with a circular section spaced from each other by the pin 14. The rotor R comprises a rotation member 13 and a ring 16. These elements are located internally to the magnets 15. The rotor R rotates around the axis of rotation X. A member 18 is attached to the frame 17. It is this member 18 and its arrangement with the frame 17 that we will be interested in below. All these elements are conventional and known in themselves with the exception of the member 18. The motor 10 here forms a brushed, commutator, wound rotor and direct current motor operating at a voltage of 12 V.

[0028] The member 18 is of generally cylindrical shape of revolution with a circular profile in a plane perpendicular to the axis X of rotation of the motor. Its external surface is smooth. It does not form a complete cylinder because it has a rectilinear slot 19 running from one longitudinal end of the member to the other. This slot makes it possible to give a certain latitude to the radius of the member 18. Indeed, the member 18 extends around the carcass 17 of the motor. Depending on the diameter of the latter, the member 18 can be adjusted, to a certain extent, to the carcass, thanks to the slot 19, the width of which is then more or less important.

[0029] As seen in the figure 4 , the member 18 is attached to the casing 17 of the motor 10. The Figure 5 schematically shows the arrangement between the member 18 and the frame 17.

[0030] The member 18 comprises three layers in the present embodiment. It thus comprises first of all an external layer 21 of magnetic steel. This layer can also be called "sheet metal". Then, a layer of elastomeric material 22, and finally a second sheet metal 23, that is to say another layer of magnetic steel, this time internal. These three layers are joined to each other and follow one another in this order in the radial direction, so that the two internal 23 and external 21 sheets form a sandwich around the elastomeric layer 22. The second internal sheet metal is also in contact with the carcass 17, since it is affixed thereto.

[0031] We therefore see that the member 18 comprises a cylindrical wall of revolution comprising in particular a sheet metal 21 located at a distance from the carcass 17.

[0032] Thus, when the engine is running, the vibrations emitted inside the casing 17 are transmitted by the latter to the sheet metal 23, which absorbs them in part and transmits the residual part to the elastomer layer 22 which absorbs a large part of the remaining vibrations, before the rest of the vibrations are transmitted and absorbed in large part by the external sheet metal 21. Thus, the noise generated by the engine and transmitted by its casing 17 is muffled to a large extent by the member 18 and its arrangement in three layers. In addition, this member 18 also makes it possible to limit magnetic losses by increasing in some way the thickness of the casing with the two layers of magnetic steel 23 and 21. Without this, the magnetic losses could disturb the other elements of the braking device or other elements of the vehicle.In this regard, thanks to the slot 19, the elasticity of the member allows in the present embodiment to ensure strong contact between the internal sheet 23 and the carcass 17. This contact ensures the guidance of the magnetic field from the carcass 17 to the member 18. The greater the contact between the carcass and the member, the better the magnetic field will be guided and the magnetic losses will be all the more limited. The slot 19 therefore allows the member 18 to be placed as close as possible to the carcass 17 to limit magnetic losses.

[0033] The added organ 18 therefore has a dual function: to limit magnetic losses and reduce motor noise.

[0034] Other embodiments not forming part of the invention will now be described, illustrated schematically in figures 6 to 8 .

[0035] The 20 engine of the figure 6, which forms a second embodiment, extends around its axis of rotation X' and has a member 28 attached to the frame 17. This member 28 comprises, as in the previous embodiment, two sheets 24 and 25, separated this time not by a layer of material but by a space empty of part (and filled with air). This is the difference with the previous embodiment. The two sheets 24 and 25 are similar to the sheets 21 and 23 of the previous embodiment, and are connected together by rings 29 forming spacers. The space 26 allows the sheet 25 not to transmit the vibrations of the motor 20 directly and entirely to the sheet 24. The member also performs the function of limiting magnetic losses.

[0036] In the third embodiment illustrated in the figure 7, the motor 30 extends around the axis of rotation X" and has an added member 38 having an arrangement in two layers instead of three. Thus, the sheet 34 is located at a distance from the carcass 17, to which it is connected via rings 39 forming spacers and directly opposite the carcass this time. In this regard, the rings 29, of the previous mode, and 39 could moreover be replaced by any other means of connection between the two cylindrical faces which they respectively connect.

[0037] In the fourth embodiment, the member 48, attached to the motor 40 extending around the axis of revolution X‴, is illustrated in figure 8 and also comprises only two layers: a sheet 44 and a layer of elastomer material 42 interposed in the radial direction between the sheet 44 and the carcass and in contact with the latter two. Here again, the member can achieve both the limitation of magnetic losses and noise.

[0038] The two-layer components 38 and 48 have the advantage of being thinner, and therefore less disruptive to the engine environment, than the three-layer components 18 and 28. The latter, however, are more reliable in terms of their noise reduction performance.

[0039] In all embodiments, other materials can be used instead of magnetic steel, such as soft iron. The elastomer layer can also be replaced by a layer of plastic, cardboard, or even grease. Indeed, several types of damping are possible to reduce noise. Examples include Coulomb damping and viscosity damping.

[0040] Of course, many modifications can be made to the invention without departing from its scope.

[0041] Thus, we can imagine organs related to more than three layers.

[0042] Furthermore, the slot 19 is not necessarily rectilinear, it can have any other shape. In the same way, an added member according to the invention can have a profile other than circular, and a non-smooth surface.

[0043] Finally, an attached member according to the invention can be used in any electric motor, and not only for motors of electric braking devices.

Claims

1. A component (18) for an electric motor (10) with a housing, comprising a cylindrical wall of revolution having a slot (19) extending from one longitudinal end of the wall to the other, the wall comprising an outer sheet (21) and an inner sheet (23) spaced apart from each other, characterised in that the inner (23) and outer (21) sheets are separated by a layer of material (22) capable of absorbing vibrations, the layer of material being in contact with the inner (23) and outer (21) sheets.

2. Electric motor (10) comprising a cylindrical casing (17) and a component (18) according to the previous claim, characterised in that the member is fitted around the casing, the inner sheet (23) being in contact with the casing (17) and the outer sheet (23) being spaced apart from the casing (17).

3. Motor (10) according to the previous claim, wherein the layer of material (22) comprises a viscoelastic material.

4. Motor (10) according to claim 2, wherein the layer of material (22) comprises an elastomeric material.

5. Motor (10) according to claim 2, wherein the layer of material (22) comprises a plastic material.

6. Motor (10) according to any of claims 2 to 5, wherein the inner and outer sheets (21, 23) comprise magnetic steel.

7. An electric vehicle braking device, comprising a motor (10) according to any of claims 2 to 6.