GB2290064A

GB2290064A - Heated rear-view mirrors

Info

Publication number: GB2290064A
Application number: GB9511279A
Authority: GB
Inventors: Claudio Pacotto
Original assignee: Magneti Marelli SpA
Current assignee: Marelli Europe SpA
Priority date: 1994-06-07
Filing date: 1995-06-05
Publication date: 1995-12-13
Also published as: GB9511279D0; FR2720702A1; ITTO940468A0; IT1266722B1; DE19520075A1; FR2720702B1; ITTO940468A1

Description

1 2290064 The present invention ref ers to an external rear-view mirror

having a heating device for the reflective sheet.

Rear-view mirrors with a reflective sheet heating device or defroster are known for eliminating the condensation which in certain atmospheric conditions can form on the surface of the reflective sheet.

Mirrors of the aforesaid type are known in which the heating device essentially comprises a resistor carried on an insulating layer fixed to the back of the reflective sheet. The resistor can be made, for example, from a wire or graphite mesh, and the support from one or more layers of synthetic material such as vinyl resin.

The known heating device has several disadvantages.

In particular. the electrical current consumption is relatively high; this is not only disadvantageous in itself, for obvious reasons of energy consumption and size of the electrical unit of the vehicle, but also leads to an increased cost of the associated electronic control devices.

In addition, manufacturing and assembly costs of the 2 heating device are increased, and this leads to an increase in the overall cost of the mirror.

The use of mirrors with a heating device has until now been limited to higher specification vehicles.

Finally, the range of values of conventional resistors converts into a relatively high probability that in practice the performance of the heating device does not achieve the theoretical design values.

The object of the present invention is to provide an external rear-view mirror for a vehicle, which is free of the above-mentioned disadvantages of known mirrors.

is This object is achieved by the present invention, in that it relates to an external rear-view mirror for a motor vehicle, of the type comprising a hollow support body. a reflective sheet housed in the said body and an electrical heating device located adjacent a rear surface of the said reflective sheet, the said heating device comprising resistive means and means for connecting the said resistive means to an electrical system of the said motor vehicle, characterised in that the said resistive means comprise at least one resistive silicon plate.

For a better understanding of the present invention, several preferred embodiments are hereinafter described, r, t R 3 purely by way of non-limitative example, with reference to the accompanying drawings, in which:

Figure 1 is a rear elevation of a rear-view mirror f or a motor vehicle f ormed according to the principles of the present invention, with parts removed for clarity; Figure 2 is a partial section taken on the line IIII of Figure 1; Figure 3 is a partial section taken on the line IIIIII of Figure 1; Figures 4, 5 and 6 are similar to Figure 3, showing different embodiments of the present invention.

With reference to Figures 1 and 2, the reference numeral 1 indicates in its entirety an external rear-view mirror is for a motor vehicle.

The mirror 1 essentially comprises a hollow body2 f ixable to the body of the vehicle by a support arm 3, and a reflective sheet 4 housed in the body 2, close to a frontal aperture 5 (Figure 2) of the body.

The sheet 4 is fixed, as will be described better in the following, to a support plate 6 which is in turn attached to the body 2 by means of an orientation adjustment device 7 of known type which will therefore not be described in detail.

Finally, the mirror 1 has a heating device a attached to 4 a rear surf ace 9 of the ref lective sheet 4, f or the purpose of heating it so as to eliminate condensation from a frontal surface 10 of the sheet.

According to the present invention. the heating device a comprises a pair of resistive silicon plates 11, which are f ixed to a layer 14 of material of high thermal conductivity, for example aluminium, with which the rear surface 6 of the reflective sheet'4 is covered.

Finally. the device 8 includes an electrical supply circuit 15 in parallel with the plates 11, described in greater detail in the following.

The plates 11 have a rectangular shape and much smaller dimensions than the surface 6, and therefore cover only limited portions of it. Such plates are preferably made, in a way known per se. from a ceramic aluminium nitride support with a covering of polycrystalline silicon doped with boron, and are attached to the aluminium layer 14 by an adhesive 12, for example of the cyano-acrylic type.

A layer 16 of double-sided adhesive material, of conventional type, is disposed -over the whole of the surface of the layer 14 which is free from the plates 11 for fixing the reflective sheet 4 to the support plate 6.

The supply circuit 15 f or the plates 11 is essentially 1 made from a pair of parallel elongate sheets 17 placed on opposite sides of the plates. The sheets 17 are fixed to the sheet 4 by the double-sided adhesive layer 16. over which they are positioned. The sheets 17 have respective electrical terminals 18. suitable for cooperating in use with a supply connector 19 (illustrated schematically in outline in Figure 2) connectable to an electrical system of the vehicle; the sheets 17 also have respective contact projections 20 located over the plates 11 and 10 joined thereto by solder spots 21 (Figures 1 and 3).

When the mirror is assembled, in a conventional manner.

the reflective sheet 4 is attached to the support plate 6 by means of the layer 16 of double-sided adhesive. The sheets 17 are therefore interposed between the aforesaid layer and the plate 6 (Figure 2); the adhesion of the layer 16 to the plate 6 is not however affected by the thickness of the sheets 17, being of such a small thickness and amply compensated f or by the def ormability of the layer 16.

In use,, the heat produced by the plates 10 diffuses through the entire reflective sheet 4 from the aluminium layer 14.

Figures 5 and 6 illustrate variants in the electrical connection between the projections 20 and the plates 10, in which the soldering is not used.

6 In particular, in the example of Figure 5 the projections 20 from the sheets 17 are curved outside the plane of the sheets and have respective extremities 22 folded back towards the plane; when the sheets 17 are attached to the layer 16. the extremities 22 of the projections 20 cooperate with the plates 10 with an elastic pre-loading between the projections 20 and the plates 11.

In the example of Figure 6, the projections 20 co-operate with the associated plate 11 by respective contact points 23.

Finally. Figure 4 illustrates an alternative embodiment in which the strips 17 are integrated in the support plate.

From an examination of the characteristics of the mirror 1 according to the present invention the advantages obtained are evident. Among other things, for the same effect, the silicon plates 11 have a lower current consumption than conventional resistors. This gives an energy saving as well as a reduction in the costs of associated wiring harness and electronic control.

In addition, the manufacturing and assembly costs of the heating device are reduced.

Finally, modern techniques of semiconductor production i 8

Claims

CLAIX5

1. An external rear-view mirror (1) for a motor vehicle, of the type comprising a hollow support body (2), a reflective sheet (4) housed in the said body (2) and an electric heating device (8) adjacent a rear surface (9) of the said reflective sheet (4), the said heating device (8) comprising resistive means (11) and connection means (17) for connecting the said resistive means (11) to an electrical system of the said motor vehicle, characterised in that the said resistive means comprise at least one resistive silicon plate (11).

2. A mirror according to Claim 1, characterised in that the said resistive plate (11) faces a portion less than the whole area of the said rear surf ace (9) of the said reflective sheet (4), and in that the said heating device (8) includes a layer (14) of material of high thermal conductivity covering the said dorsal surface (9) of the said reflective sheet (4) and interposed between this and the said resistive plate (11).

3. A mirror according to Claim 1 or 2, characterised in that the said plate (11) is secured by adhesive to the said layer (14) of material of high thermal conductivity.

4. A mirror according to Claim 2 or 3, characterised in that it comprises a support plate (6) for the said 7 enable resistive plates to be obtained characterised by little variation in resistance values; leading to great reliability and uniformity in the functioning of the heating devices produced with them.

9 reflective sheet (4), the said reflective sheet (4) being f ixed to the said plate (6) by means of a layer of adhesive material (16) applied to at least one portion of the said layer (14) of material of high thermal conductivity not covered by the said plate (11).

5. A mirror according to Claim 4, characterised in that the said means for connecting the said plate (11) to the electrical system of the vehicle comprise a plurality of conductive strips (17) interposed between the said layer of double-sided adhesive material (16) and the said support plate (6).

6. A mirror according to Claim 4, characterised in that the said means f or connecting the said plate to the electrical system of the vehicle is integrated in the said support plate (6) of the said reflective sheet (4).

7. A mirror according to any of the preceding claims, characterised in that it includes at least two said plates (11) connected in parallel.

8. An external rear-view mirror for a vehicle, substantially as described and illustrated in the accompanying drawing.