GB2069120A

GB2069120A - Preventing condensation in headlamps for motor vehicles

Info

Publication number: GB2069120A
Application number: GB8100334A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-02-07
Filing date: 1981-01-07
Publication date: 1981-08-19
Also published as: DE3004413A1; JPH0113604B2; IT1135304B; GB2069120B; JPS56126201A; DE3004413C2; FR2475474B1; FR2475474A1; IT8119516A0

Abstract

To prevent the deposition of condensate on the inner surfaces of a headlamp, especially for motor vehicles, and to prevent spray water from entering the interior of the headlamp, the housing 11 of the headlamp has an air outlet 16 in the upper section and an air inlet 21 in the lower section. The air outlet issues into a duct 15 the upper opening 18 of which lies within the travelling air flow. <IMAGE>

Description

SPECIFICATION A headlamp for motor vehicles State of the Art The problem of damaging the lens and the reflector of headlamps by condensed water vapour has not yet been satisfactorily solved despite many proposals. One known solution consists in replacing the air in the interior of the headlamp by atmospheric air through openings; the increase in pressure due to the heated inner air when the incandescent bulb is switched on is used for this purpose.

However, in practice, the difficulty with this kind of ventilation is that with a sufficient exchange of air the sealing against spray water is insufficient, on the other hand with sufficient sealing against spray water the achievable exchange of air does not sufficiently prevent or reduce the damage to the inner surfaces of the headlamp.

Advantages of the Invention With the headlamp for motor vehicles according to the invention, simple means are provided so that condensate is not deposited on the inner surfaces of the headlamp and spray water does not enter the interior of the headlamp.

The invention is based on the concept of producing a suction at the air outlet which is produced by the travelling air flow during travelling and by the chimney effect when stationary. Contrary to the vehicle lights provided with a chimney already known before the turn of the century, the duct in accordance with the invention is arranged in the side or rear region of the headlamp.

Advantageous further developments of the invention are described in the sub-claims. With the construction of a so-called housing headlamp according to claim 2, a ventilation arrangement is provided which may be fitted to normal housings without additional expenditure. The required spray water protection is achieved even under unfavourable travelling conditions when the headlamp is further developed according to claim 3 or claim 4. The housings of most headlamps are produced from plastics. In that case, three easily producible duct arrangements are proposed according to claims 7 to 9.

Drawing Two embodiments of the invention are illustrated in the drawing and are described in detail in the following specification. Figure 1 shows the housing headlamp incorporated in the motor vehicle provided with the air flows in a reduced side view; Figure 2 is the rear view of a housing headlamp with an exhaust air duct on the housing to a reduced scale; Figure 3 shows the rear view of the housing headlamp with the exhaust air duct in the hood, on a reduced scale; and Figures 4 to 6 show three duct arrangements in an enlarged longitudinal section.

Description of the Embodiments A housing headlamp 10 consists essentially of a housing 11 with a hood 12, both are produced from plastics material, a lens 1 3 and a reflector 20 with an incandescent bulb 9. The headlamp 10 is fixed to the vehicle body by means of elements which are not shown. An air outlet 1 6 a lower and upper opening 1 7, 1 8 of which issues into the duct 15, is arranged in the upper side section of the housing 11. The upper duct opening 1 8 slopes downwards towards the rear so that its front edge 34 projects into the travelling air flow. A reflector 20 is adjustably fixed in the interior 1 9 of the headlamp 10 and an air inlet 21 is arranged in the housing 11 opposite the air outlet 1 6.

When travelling, atmospheric air flows through the upper opening 18 of the duct 15 so that, on the basis of the theoretical principles of Bernoulli, it produces a suction which also produces a negative pressure in the air outlet 1 6 and entrained air flows out from the interior 1 9. This causes a subsequent flow of atmospheric air through the air inlet 21 into the interior 19 of the headlamp 10.

With the vehicle stationary and the incandescent bulbs 9 switched off, the duct 1 5 acts as a chimney so that a suction also exists at the outlet 1 6 which causes an exchange of air in the headlamp interior 1 9 although with substantially less intensity.

The housing headlamp 30 in Figure 2 has a housing 31 of substantially rectangular shape. The tubular duct 1 5 is arranged at the top in the side section in such a manner that its upper opening 1 8 lies within the travelling air flow and moreover the edge 34 of the opening 1 8 facing the air flow is higher so that on this side the travelling air flow streaks past; this produces a suction in the duct 1 5. The lower opening 17 is in the lee of the travelling air flow. A tube piece 35 is arranged in the lower section 32 of the housing 31 opposite to the duct 15 and its two openings 37, 38 are not traversed by the travelling air flow.

A respective fitting 36 connects the interior 39 to the duct 1 5 and to the tube portion 35 wherein the end section of each of the fittings 36 is so bevelled that spray water forced into the duct 1 5 or into the tube portion 35 is not forced into the housing interior 39. The bevelled end portion of the fitting issuing into the duct 1 5 causes an increase in the velocity of the air flow at the duct restriction and thus a higher suction effect in the interior. The air flows are indicated by arrows.

The duct 45 in Figure 3 is integrated in a hood 42 which closes the housing 41 of the housing headlamp 40 towards the rear. The air outlet likewise formed as a fitting 36 connects the housing interior 39 to the duct 45 the upper opening 1 8 of which lies in the travelling air flow and the lower opening 1 7 of which is shielded from the air flow.

The air inlets are formed as nozzles 43 which are both mounted on the underside of the housing 41. The suction in the region of the upper opening 18 and of the fitting 36 as well as the chimney effect is as previously described.

Figure 4 shows, in section, the housing 51 produced from plastics material provided with a moulded on fitting 56 which has an external annular groove 57. A rib 58 which changes into inwardly directed latches 59 which are radially outwardly resilient, projects from the duct 55 likewise produced from plastics material. On assembling the duct 55 with the housing 51, the latches 59 clip into the annular groove 57 so that both parts are releasably fixed to one another with a kind of snap connection.

In the arrangement according to Figure 5, the fitting 66 consists of a resilient plastics material and has a sleeve 67 with an annular lip 60 and an annular latch 64. The fitting 66 is pushed into the duct 65 made of plastics material and this plug-in position secures the annular lip 60. The housing 61 has an aperture 62 behind which the annular latch 64 on the fitting 66 engages when the duct 65 is assembled with the housing 61. A plurality of projections 63 moulded onto the housing 61 retain the duct in the prescribed position.

Figure 6 shows another plastics arrangement wherein the fitting 76 and two cheeks 72 (lying one behind the other in the figure) project integrally from the housing 71. A strip 73 of plastics material has a plurality of latches 74 which, on assembly of the strip with the cheeks engaged in a groove 75 in each of the cheeks 72 and thus form a releasable connection.

Claims

1. A headlamp for motor vehicles comprising the features: a) the headlamp has an air inlet in its lower section and an air outlet in its upper section, b) a duct is so arranged in the side or rear section of the headlamp that the forward edge of the rearwardly sloping duct opening projects into the travelling air flow and c) the air outlet issues into the duct.

2. A housing headlamp in particular according to claim 1 comprising the features: d) the duct is arranged in the upper side section of the housing and e) the air inlet is arranged at the opposite lower section of the housing.

3. A headlamp according to claim 2 comprising the features: f) the air inlet is formed as a fitting, g) a tube portion is so arranged on the headlamp that the upper and lower tube portion openings lie in the lee of the travelling air flow and h) the fitting connects the tube to the interior of the headlamp.

4. A housing headlamp in particular with a hood according to claim 1 comprising the features: i) the chimney is arranged on the hood and j) the air inlet is formed as a nozzle on the underside of the housing.

5. A headlamp according to one of claims 2 to 4 comprising the features: k) each fitting is so formed that water forced into the upper opening of the duct and into the upper opening in the tube portion is not forced into the interior of the headlamp, I) the fitting reduces the cross-section of the duct and thus increases the velocity of the air passing through the chimney at this location.

6. A headlamp according to one of the preceding claims comprising the feature: m) the junction of the fitting forming the air outlet lies substantially at two-thirds the height of the duct.

7. A headlamp comprising a housing or a hood made of plastics material according to one of the preceding claims comprising the feature: n) the duct and the tube portion are made of plastics material and are fixed to the housing or to the hood by means of a snap connection.

8. A headlamp comprising a housing or a hood made of plastics material according to one of claims 1 to 6 comprising the feature: o) the duct and the tube portion is moulded onto the housing or onto the hood integrally.

9. A headlamp according to claim 8 comprising the features: p) two side cheeks project from the housing or from the hood and q) a strip can be latched preferably in both cheeks and with them forms the duct.

10. A headlamp for motor vehicles, substantially as herein described with reference to Figure 1, Figure 2 or Figure 3, with or without any of the modifications of Figures 4 to 6, of the accompanying drawings.