GB2468289A

GB2468289A - Vehicle door mirrors

Info

Publication number: GB2468289A
Application number: GB0903529A
Authority: GB
Inventors: Matthew Weaver
Original assignee: Nissan Motor Manufacturing UK Ltd
Current assignee: Nissan Motor Manufacturing UK Ltd
Priority date: 2009-03-03
Filing date: 2009-03-03
Publication date: 2010-09-08
Also published as: GB0903529D0

Abstract

A mirror assembly 10 for the exterior of a vehicle, the mirror assembly 10 comprising: a reflective element 12 and a head 20 for housing the reflective element 12. The head 20 further comprising: a leading face, arranged to face the direction of vehicle travel. A trailing face, distal from the leading surface and arranged to surround the reflective surface of the reflective element 12. An air inlet 40 positioned on the leading face; an air outlet 50 positioned adjacent to the trailing face; and a mounting 15 for pivotably supporting the reflective element, wherein the air inlet is in fluid communication with the air outlet via an air duct 35 integrated within the head 20. In a second embodiment the mirror assembly has a two piece vent guide having an annular duct bladder (160, Figure 5), vent skirt (132, Figure 5), duct valve (130, Figure 5) and valve actuator (150, Figure 5) arranged to be optimise the air flow through the mirror assembly.

Description

IMPROVEMENTS IN VEHICLE EXTERIOR MIRRORS

Field of the invention

The present invention relates to a door mirror for a vehicle and in particular, to an aerodynamic door mirror and control method thereof.

Background of the invention

Motor vehicles are commonly fitted with external mirrors to aid the driver in safely negotiating a parking manoeuvre or to see other road users behind him during overtaking or merging into traffic. Such mirrors are known as door mirrors as they are commonly mounted to the exterior of the vehicle door.

Such mirrors need to be large enough to provide a useful field of view for the driver and recent amendments to European legislation will require vehicle manufacturers to fit even larger mirrors than before in an attempt to improve road safety.

One significant drawback in providing larger door mirrors is the increase in aerodynamic drag caused by the disruption in airflow around the vehicle when the vehicle is driving at speed. To manage this, some vehicle manufacturers have tried to reduce the affect the door mirror has on the vehicle's overall drag co-efficient by creating door mirrors with a streamlined profile.

Door mirrors are an assembly of four main components: a reflective element or mirror, a head, in which the mirror is housed; an arm, one end of which supports the head, and mounting means for mounting the other end of the arm to the vehicle door. The mounting means for the door mirror is often provided via a sail panel, so-called because of its distinctive triangular shape.

In recent years, the motor industry has made considerable efforts to improve vehicle efficiency and improve fuel economy by reducing aerodynamic drag. The result of this effort has been to streamline the profile of the head and the arm of the door mirror to as to minimise their contribution to the overall drag co-efficient of the vehicle.

One feature of the door mirror, however, has not been addressed, namely the affect of the predominantly vertical reflective element or mirror contributes to the overall drag co-efficient of the door mirror assembly itself. Where considerable effort has been made to streamline the leading edges of the door mirror, the trailing edge of the door mirror is truncated sharply by the flat vertical face of the reflective element. This truncated trailing edge contributes considerably to the overall drag co-efficient of the door mirror assembly as a whole. This has not been effectively addressed to date because nothing may be placed over the reflective element to minimise air turbulence and the resulting drag without obscuring the user's view of the mirrored surface.

It is against this background that the present invention seeks to improve upon the known vehicle door mirror by providing a door mirror assembly comprising means improving the laminar flow of air around the head and reflective element.

Summary of the invention.

According to an aspect of the present invention there is provided a housing for a vehicle mirror assembly, comprising: a leading surface, arranged to face in the general direction of vehicle travel; a trailing surface for supporting a reflective element; air inlet means positioned on the leading surface; and air outlet means positioned at or adjacent to the trailing surface and in fluid communication with the air inlet means via a duct formed within the housing.

Advantageously, the present invention allows for some balancing of air pressure between a high-pressure zone in front of the leading surface of the mirror assembly, with a low pressure zone at the trailing surface.

According to an embodiment, the cross-sectional area of the air inlet means is greater than the cross sectional area of the air outlet means such that air flowing through the duct is accelerated.

Advantageously, the present invention provides the mirror assembly with a supply of high-pressure air, whose pressure is dependent on vehicle speed. This high-pressure air may be directed as necessary to any specific area adjacent to the trailing surface as may provide the greatest aerodynamic benefit to the mirror assembly and the vehicle to which it is mounted.

According to an embodiment, a housing for a vehicle mirror further comprising: an arm, arranged to pivotably connect the head to the mounting means.

Advantageously, mounting the mirror assembly of the present invention to the vehicle via an arm allows for the reflective element to be positioned away from the side of the vehicle to increase the field of view available to the user.

According to an embodiment, the air outlet is arranged between the periphery of the reflective element and the head.

Advantageously, the present invention not only improved the aerodynamic performance of the mirror head but allows for some of the high-pressure air exiting the air outlet to be directed at least partly across the reflective element to clear it from water droplets.

According to an embodiment, at least part of the head is formed from a transparent polymer arranged to permit a substantial part of the air duct to be visible from the outside of the head.

Advantageously, the forming of the present invention from a transparent polymer allows the user to see if the air duct is blocked and take appropriate action to clear it. Forming the head of the mirror from a transparent polymer minimises the appearance of the mirror assembly to the user, allowing them the greatest possible field of view around the vehicle. Additionally, forming the head of the mirror from transparent polymer allows more ambient light into the occupant compartment.

According to an embodiment, the air outlet is independent of the orientation of the reflective element.

Advantageously, the present invention separates the aerodynamic requirements of the mirror assembly from the conventional requirements associated with viewing angles and adjustment of orientation of the reflective element to accommodate drivers of differing statures. In this way, the aerodynamic benefits of the present invention are not significantly compromised by the orientation of the reflective element.

According to an embodiment, the mirror assembly further comprises: a sensor; a valve; control means; and a valve actuator, wherein the control means monitors the sensor which is arranged to measure the force exerted on the head when the vehicle is in motion and is arranged to vary the flow of air through the duct in response to that force.

According to an embodiment, the mirror assembly further comprises a second sensor and, wherein the second sensor is arranged to measure pressure differential between the leading edge and the trailing edge when the vehicle is in motion and the control means is arranged to vary the flow of air through the duct in response to that differential.

Advantageously, the present invention allows for means of optimising the aerodynamic performance of the mirror assembly by optimising airflow in response to vehicle speed and optimising airflow in response to a change in vehicle speed.

According to an embodiment, the air duct is provided with a light source and the air duct is arranged to form a light guide to direct light from the light source to an exterior surface of the mirror assembly.

Advantageously, the present invention allows for the air duct which is substantially aligned with the direction of travel of the vehicle to further function as a light guide. In this way, a single light source is required to illuminate both the leading and trailing surfaces of the mirror assembly providing an exterior vehicle mirror with integrated turn signal or indicator lamp.

According to an embodiment, the control of the valve may selectively be used to direct airflow across the reflective surface of the reflective element so as to clear water droplets away from the reflective surface when the vehicle is in motion.

Advantageously, the present invention allows for the high-pressure air to be directed or re-directed as required. Optimising the aerodynamic properties of the mirror assembly and the functionality of the reflective element, as a means of improving rearward visibility without obstruction.

According to another aspect of the present invention there is provided a method of controlling airflow around and through a mirror assembly mounted to the exterior of a vehicle, the method comprising: measuring forces applied to the mirror assembly by a measuring system when the vehicle is stationary; calibrating the system based on the forces measured when the vehicle is stationary; measuring the vehicle speed; measuring forces applied to the mirror assembly when the vehicle is in motion; comparing the forces measured when the vehicle is in motion with the theoretically optimum force for a given speed; determining the discrepancy between the measured force and the theoretically optimum force for said given speed and adjusting a valve means within the mirror assembly to optimise the airflow therethrough in dependence of the calculated discrepancy.

Advantageously, the method of controlling the airflow through and around the door mirror assembly optimises the aerodynamic performance of the door mirror of the present invention throughout the speed range of the vehicle.

It will be appreciated by one skilled in the art that the door mirror and control means of the present invention may be suitable for use in applications unrelated to vehicles.

It will also be appreciated by one skilled in the art that the preferred and/or optional features relating to the present invention may be used either alone or in appropriate combination.

Brief Description of the Drawings

In order that the invention may be more readily understood reference is made, by way of example only, to the accompanying drawings in which: Figure 1 is side view of a known vehicle door assembly; Figure 2a shows a plan view of a known door mirror assembly and Figure 2b shows the door mirror of Figure 2a in use showing the typical airflow past the mirror assembly; Figure 3 shows a section through the side of a door mirror of the present invention; Figure 4a shows a plan view of the door mirror assembly of the present invention and Figure 4b shows the door mirror of Figure 4a in use showing the typical airflow past and through the mirror assembly; and Figure 5 shows a section through the side of an alternative embodiment of the door mirror of the present invention.

The present invention seeks to improve the aerodynamic properties of known door mirror assemblies. The present invention achieves these improvements by incorporating a feature in the head of the door mirror arranged to greatly improve the laminar flow of air around the head and past the reflective element.

Referring to Figure 1, a side view of a known vehicle door 1, complete with side window or drop glass 2, exterior door handle 3 and door mirror assembly.

Door mirrors are an assembly of four main components: a reflective element or mirror(not shown in Figure 1), a head 6, in which the mirror is housed; an arm 5, one end of which supports the head, holding the head a set distance from the side of the vehicle body, and mounting means for mounting the end of the arm 5 distal from the head 6 to the vehicle door 1 provided by a sail panel 4.

Figure 2a shows a known door mirror in plan view. The sail panel 4, arm 5 and head 6 may be clearly seen mounted to the vehicle door 1. Figure 2a also shows in phantom the location of the reflective element 12.

Figure 2b shows a representation of the air flowing around the door mirror assembly when the vehicle is in motion. Air contacting the leading edge of the door mirror assembly is compressed by the vehicle travelling forward causing a localised high pressure zone. There is little or no air in the region of the trailing edge of the head 6, adjacent to the reflective element 12, this produces a localised low pressure zone.

The airflow around the leading edge of the head 6 is relatively laminar but the truncated profile of the trailing edge of the head 6, combined with the compressed, high pressure air meeting the low pressure zone, causes turbulent airflow around the trailing edge of the head adjacent to the reflective element 12.

This turbulent airflow greatly increases the aerodynamic drag when the vehicle is in motion.

Figure 3 shows a section through a door mirror assembly 10 of the present invention. The reflective element 12 is pivotably mounted via a balI 14 extending from the back of the reflective element. The ball 14 is received by a co-operating cup 15 mounted by an integrated feature (not shown) to the head 20. From the view provided in figure 3, the head 20 substantially surrounds the other components of the mirror assembly located at the end of the arm (not shown) distal from the vehicle (also not shown).

The mirror assembly 10 further comprises a rear trim piece. The trim piece 10 is arranged to conceal the ends of the mirror even if the orientation of the mirror has been adjusted to the extremes of movement available from the co-operation between the ball 14 and cup 15. The mirror assembly is orientated to have a leading edge and a trailing edge. The trailing edge is adjacent to the reflective element 12 and the leading edge is orientated to substantially align the mirror assembly 10 with the direction of vehicle travel.

The leading edge of the head 20 is provided with an air inlet 40 and there is an air outlet 50 positioned around the perimeter edge of the reflective element 12.

The air inlet 40 is arranged to be in fluid communication with the air outlet 50 via a passageway or duct 35 integrated within the head 20 of the mirror assembly.

When the vehicle is in motion the air inlet 40 is arranged to allow some of the air which is compressed by the leading edge of the mirror assembly 10 to pass through the duct 35 and exit via the air outlet adjacent to the reflective element 12. In this way the mirror of the present invention is arranged to at least partially balance the difference in air pressure between the high pressure and the low pressure zone at the trailing edge. In addition, the duct 30 may be configured to accelerate the air flowing to the air outlet 50, creating a jet of high speed air which may be directed as required. These jets of high speed air may be directed to specific areas around the mirror assembly or adjacent door to improve the aerodynamic performance of the vehicle. The position, number and size of the air inlet and outlet may be adjusted to optimise the performance for a given design of door mirror assembly and vehicle combination.

Also shown in Figure 3 is a substantially conical vent guide 30. The vent guide is arranged to improve airflow around the reflective element 12 and associated mounting means 14, 15. The shape of the vent guide 30 may be adjusted as required to control the flow of air through the duct 35 as required. The leading edge of the vent guide 30 is tapered behind the air inlet 40 so as to provide the greatest possible surface area for air to air to enter the duct 35 via the inlet 40.

The trailing edge of the of the vent guide 30 extends beyond the perimeter of the reflective element 12 so as to prevent the orientation of the reflective element 12 having any influence over the aerodynamic properties of the door mirror 10.

Figure 4a shows a plan view of a door mirror of the present invention. Figure 4b shows a representation of the air flowing around the door mirror assembly 10 when the vehicle is in motion.

Figure 5 shows an alternative embodiment of the mirror of the present invention.

In the embodiment shown in Figure 5, the one-piece vent guide 30 shown in Figure 3 has been replaced by a two-piece vent guide 300. In this embodiment, vent guide 300 comprises a vent guide skirt 132, a duct valve 130 and a valve actuator 150. The vent guide skirt 132 is mounted within the head 20 in the same way as vent guide 30 of Figure 3. The leading edge of the vent guide skirt 132 provides a suitably rigid support for the valve actuator 150 to which the duct valve 130 is mounted.

In the embodiment shown in Figures, the position on the duct valve 130 between the reflective element 12 and the air inlet 40 may be varied in dependence on a signal from a controller (not shown). Moving the duct valve 130 forwards into the air inlet 40 restricts the airflow into the air inlet 40. Moving the duct valve 130 backwards away from the air inlet 40 effectively opens the air inlet 40 to allow more air to enter.

A passageway or duct connects the inlet 40 with the outlet 50 as with the example shown in Figure3, however the shape and volume of this duct 135 may be varied. By adjusting the valve actuator 150 the length of the duct 135 may be varied. The shape and volume of duct 135 may be further adjusted by inflating a generally annular duct bladder 160. This inflatable bladder 16 may be used to restrict the duct 135 which tends to accelerate the air flowing past the bladder 160. Duct valve 130 may be arranged to be flexible so that when the bladder 160 is inflated by an actuator (not shown) the base of the duct valve 130 is expanded to further restrict the duct 135 as desired.

The shape of the duct within the head 20 may be optimised for packaging within any head 20 of a given shape and size and the duct may be divided to provide a plurality of ducts as required.

It will be appreciated by one skilled in the art that the arm 5 of the mirror assembly 10 may also comprise an air inlet, duct and air outlet which may be distinct from or in fluid communication with corresponding features in the head 20.

In an alternative embodiment (not shown), the head is formed from a transparent polymer arranged to allow the duct or ducts and vent guide to be visible from the outside of the vehicle. Passageways to guide airflow past a vehicle may become blocked with dust or dirt borne on the air flowing through the passageway.

Providing a means to view the passageways enables the user to identify if they have become blocked and require cleaning. It is envisaged that the user will unblock the passageways at regular intervals by spraying water from a hose through the inlet. Alternatively, the user may blow any debris out of the passageways or using a workshop compressor to supply a jet of high pressure air.

In a further embodiment (also not shown), the vent guide may comprise a light guide or may be formed, at least in part, from a transparent polymer so as to provide the feature of a light guide along the surface of the vent guide. The light guide may be supplied with light by a light source integrated within the mirror assembly. As the vent guide is visible from the front of the vehicle any light carried by the light guide will also be visible. Additionally, as the vent guide extends rearward of the reflective element, any light carried by the light guide is also visible from the rear of the vehicle. Light carried by the light guide is visible from the rear of the vehicle as it illuminates the air outlet(s) around the reflective element. In this way, the door mirror may be provided with an integrated turn signal or indicator light arranged to be visible from both the front and the rear of the vehicle.

The present invention allows for an increase in area of the reflective element without adversely affecting the aerodynamic performance of the door mirror assembly 10. Additionally, the present invention may be adopted for use on an existing vehicle design without changing the way it is mounted to the vehicle. The present invention does not affect the arm 5 or vehicle mounting and only requires a change in mirror head The present invention is not limited to mirrors mounted to the door but may be equally effective if mounted in other locations around the exterior of the vehicle.

Another benefit of the present invention is that the location of the air inlet tends to truncate the leading edge of the head, so making the door mirror more compact if folded against the vehicle when the vehicle is parked.

Other advantage will be apparent to one skilled in the art and the present examples and embodiments are to be considered illustrative and not restrictive.

The invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.

Claims

CLAIMS1. A housing for a vehicle mirror, comprising: a leading surface, arranged to face in the general direction of vehicle travel; a trailing surface for supporting a reflective element; air inlet means positioned on the leading surface; and air outlet means positioned at or adjacent to the trailing surface and in fluid communication with the air inlet means via a duct formed within the housing.
2. A housing as claimed in claim 1, wherein the cross-sectional area of the air inlet means is greater than the cross sectional area of the air outlet means such that air flowing through the duct is accelerated.
3. A mirror assembly according to claim 1 or claim 2 further comprising: an arm, arranged to pivotably connect the head to the mounting means.
4. A mirror assembly according to any preceding claim, wherein the air outlet is arranged between the periphery of the reflective element and the head.
5. A mirror assembly according to any preceding claim, wherein at least part of the head is formed from a transparent polymer arranged to permit a substantial part of the air duct to be visible from the outside of the head.
6. A mirror assembly according to any preceding claim, wherein the air outlet is independent of the orientation of the reflective element.
7. A mirror assembly according to any preceding claim, wherein the mirror assembly further comprises: a sensor; a valve; control means; and a valve actuator, wherein the control means monitors the sensor which is arranged to measure the force exerted on the head when the vehicle is in motion and is arranged to vary the flow of air through the duct in response to that force.
8. A mirror assembly according to claim 6, wherein the mirror assembly further comprises a second sensor and, wherein the second sensor is arranged to measure pressure differential between the leading edge and the trailing edge when the vehicle is in motion and the control means is arranged to vary the flow of air through the duct in response to that differential.
9. A mirror assembly according to any of claims 4 to 7 wherein the air duct is provided with a light source and the air duct is arranged to form a light guide to direct light from the light source to an exterior surface of the mirror assembly.
10. A mirror assembly according to any of claims 6 to 8 wherein the control of the valve may selectively used to direct airflow across the reflective surface of the reflective element so as to clear water droplets away from the reflective surface when the vehicle is in motion.
11. A vehicle comprising a mirror assembly according to any of the preceding claims.
12. A method of controlling airflow around and through a mirror assembly mounted to the exterior of a vehicle, the method comprising: measuring forces applied to the mirror assembly by a measuring system when the vehicle is stationary; calibrating the system based on the forces measured when the vehicle is stationary; measuring the vehicle speed; measuring forces applied to the mirror assembly when the vehicle is in motion; comparing the forces measured when the vehicle is in motion with the theoretically optimum force for a given speed; determining the discrepancy between the measured force and the theoretically optimum force for said given speed and adjusting a valve means within the mirror assembly to optimise the airflow therethrough in dependence of the calculated discrepancy.