GB2501500A

GB2501500A - Method and apparatus for de-icing a screen

Info

Publication number: GB2501500A
Application number: GB1207218.7A
Authority: GB
Inventors: Colin Burbridge
Original assignee: Nissan Motor Manufacturing UK Ltd
Current assignee: Nissan Motor Manufacturing UK Ltd
Priority date: 2012-04-25
Filing date: 2012-04-25
Publication date: 2013-10-30
Also published as: GB201207218D0

Abstract

To de-ice a screen 24 which is mounted to a support 16 by an elastomeric seal 22, the screen is vibrated relative to the support. Deformation of the seal causes internal friction in the seal 22, generating heat which is conducted to the screen. The method is particularly applicable to small screens having a high ratio of screen perimeter to surface area, e.g. a screen for a camera for a lane departure warning system on a vehicle. The actuator may be an ultrasonic actuator. The actuator may be activated manually or automatically through an obscuration sensor, temperature sensor, HRW switch, or front or rear wiper switch. The screen may be surrounded by a frame, and may be mounted in a tailgate, bumper, or other panel, particularly at the rear of the vehicle. The seal material may be doped to increase heat generation and/or conduction.

Description

I

Method and Apparatus for Dc-Icing a Screen

Technical Field of the Invention

The present invention relates to a method, and to an apparatus, for dc-icing a screen. The invention is particularly, but not exclusively, concerned with a method and an apparatus for dc-icing a screen for a camera mounted on a vehicle.

Background to the Invention

Many vehicles are fitted with cameras for detecting obstacles or road markings. For example, a camera may be used to detect road markings as part of a lane departure warning system. To protect the camera and its lens from the environment, the camera is usually mounted in a housing or other enclosure and looks out through a small screen or window. Operation of the camera can be impaired if the screen becomes covered with ice.

Conventional arrangements for dc-icing screens include the use of electrical resistive heating elements embedded in or mounted to the screen; or the use of systems for blowing hot air onto the screen. Such arrangements, whilst effective, are complex and difficult to implement for a small camera screen, especially when the camera is mounted towards the rear of the vehicle and facing the road surface.

Furthermore, applying metallic conductive coatings to a screen may affect the transmission of electromagnetic radiation outside the visible spectrum through the screen. Accordingly, this technology may be not suitable for use in dc-icing screens for sensors configured to detect electromagnetic radiation outside the visible spectrum.

There is a need then for an alternative method of dc-icing a screen, and in particular a small screen for a camera and the like, which overcomes or at least mitigates some or all of the disadvantages of the known methods.

There is also a need for an alternative apparatus for dc-icing a screen, and in particular a screen for a camera or the like, which overcomes or at least mitigates some or all of the disadvantages of the known apparatus.

Summary of the Invention

According to a first aspect of the invention, there is provided a method of de-icing a screen mounted to a support by means of an elastomeric seal, the method comprising vibrating the screen relative to the support so as to cause deformation of the seal such that internal friction within the seal generates heat which is conducted to the screen.

The screen may have a high ratio of perimeter to surface area.

Preferably the screen is vibrated at high frequency and low amplitude.

The method may comprise vibrating the screen by means of an actuator, which may be an ultrasonic actuator.

The screen may be part of a screen assembly comprising an outer frame surrounding the screen. In which case, the actuator may act on the outer frame.

At least an outer edge region of the screen and a corresponding inner edge region of the support that are both engaged by the seal may be substantially planar; and the method may comprise vibrating the screen in a direction substantially parallel to the planar edge regions. The whole of the screen may be substantially planar; and the method may comprise vibrating the screen in a direction substantially parallel to the plane of the screen.

The screen may be made of a material that is substantially transparent to at least a desired range of electromagnetic radiation such as radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. The screen may be substantially transparent to visible light. The screen may be made of glass. The screen may comprise a window for a camera.

The method may be applied to a window for a camera mounted to a vehicle, such as a lane departure warning system camera.

The method may be applied to a vehicle comprising a washer jet for the window.

According to a second aspect of the invention, there is provided apparatus for dc-icing a screen mounted to a support by means of an elastomeric seal, the apparatus comprising an actuator operatively connected with the screen for vibrating the screen relative to the support.

The apparatus may be configured so that, in use, vibration of the screen causes deformation of the seal such that internal friction in the seal generates heat which is conducted to the screen.

The screen may have a high ratio of perimeter to surface area.

The actuator may be configured to vibrate the screen at high frequency and low amplitude. The actuator may be an ultrasonic actuator. The actuator may be operatively connected, directly or indirectly, with the screen.

The screen may be part of a screen assembly coiiipiising an outer frame surrounding the screen, and the actuator may be operatively connected with the outer frame.

At least an outer edge region of the screen and a corresponding inner edge region of the support that are engaged by the seal may be substantially planar; and the actuator may be configurcd to vibrate the screen in a direction substantially parallel to the planar edge regions. The whole of the screen may be substantially planar; and the actuator may be configured to vibrate the screen in a direction substantially parallel to the plane of the screen.

The screen may be made of a material that is substantially transparent to at least a desired range of electromagnetic radiation such as radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. The screen may be substantially transparent to visible light. The screen may be made of glass. The screen may comprise a window %r a camera. The screen may have a hydrophobic coating at least on its exterior surftce.

The screen may comprise a window thr a camera mounted to a vchicle, such as a lane departure warning system camera. The vehicle may comprise a washer jet fbr the window.

In accordance with a third aspect of the invention, there is provided a vehicle having a camera mounted in a camera housing, the housing including a camera screen through which the camera is directed, the screen being mounted to a support by means of an elastomeric seal, the vehicle comprising apparatus ibr de-ieing the camera screen in accordance with the second aspect of the invention.

Detailed Description of the Invention

In order that the invention may be more clearly understood, an embodiment thereof will now be described -by way of example only -with reference to the sole drawing, Figure 1, which is a fragmentary, partially cutaway view from the outside of a vehicle camera window incorporating dc-icing apparatus in accordance with the present invention. The window is shown in Figure 1 on an enlarged scale for clarity.

A camera 10 having a lens 12 is mounted in a housing or enclosure 14 on a vehicle. The camera 10 may be part of a sensing system of the vehicle. In one embodiment, the camera 10 is part of a lane departure warning system of the vehicle; and is located near the rear of the vehicle, facing onto the road surface to detect road markings. The housing 14 in the present embodiment forms part of a tailgate of the vehicle and is closed at one end by a panel 16 of the tailgate. The housing though could be formed at any suitable location inside the main body or bumper of the vehicle; or it could be in the form of a camera enclosure attached to the main body.

An opening 18 is formed in the tailgate panel 16 through which the lens 12 of the camera 10 is directed. To protect the lens 12 from the external environment, the opening 18 is closed by means of a screen assembly 20 mounted to the panel 16 by means of an elastomeric seal 22. The screen assembly 20 includes a screen 24 mounted in an outer peripheral frame 26. The screen 24 is made of glass or some other material, such as a polymeric material, that is transparent to visible light. The frame 26 can be made of any suitable material; and could be made of a metallic material such as aluminium for example. The frame 26 though is not essential and could be omitted so that the screen assembly comprises only a transparent screen member 24.

The opening ISis substantially rectangular in shape with rounded corners. The periphery of the screen assembly 20 is similarly shaped for location within the opening. The screen assembly 20 is smaller than the opening 18 so that the outer periphery of the screen assembly is spaced from the inner edge of the panel 16 defining the opening. The elastomeric seal 22 is shaped as a generally rectangular annulus and has a central portion 22a that locates in the gap between the outer periphery of the screen assembly 20 and the edge region of the panel 16. A pair of opposed inwardly directed flap portions 22b extend radially inwardly from the central portion 22a for engagement on opposite sides of an outer peripheral edge region of the screen assembly 20. A pair of opposed outwardly directed flap portions 22c extend radially outwardly from the central portion 22a for engagement on opposite sides of an inner edge region of the tailgate panel 16 surrounding the opening 18. The elastomeric seal 22 removably mounts the screen assembly 20 to the panel 16 and forms a watertight seal to prevent moisture from entering the camera housing. The screen 24 in this embodiment is substantially planar, and is formed from a flat sheet of glass or other transparent material.

As so far described, the camera window arrangement is largely conventional.

In accordance with the invention, apparatus for dc-icing the screen is provided in the foim of an actuator 28 connected to the screen assembly 20 and operative to move the screen assembly relative to the support panel 16. Movement of the screen assembly 20 relative to the panel 16 is accommodated by deformation of the elastomeric seal 22.

The actuator 28 is arranged to vibrate the screen assembly 20 at a relatively high frequency and low amplitude. Internal friction in the elastomeric seal 22 as the screen assembly is vibrated generates heat, which conducts into the screen. The appropriate frequency or range of frequencies to be used depend on the specific requirements of any given application. For example, the minimum frequency required may vary in dependence on the material the screen is manufactured from, the material used for the seal, and the relative dimensions of the screen and seal amongst other factors. If necessary, an appropriate frequency can be determined through trial and error. It is advantageous, however, to select a frequency which is inaudible to the human ear, which would include for example frequencies above 16kHz.

Whilst the heat input from the elastomeric seal is relatively small, provided the screen 24 has a relatively high ratio of screen perimeter to surface area and/or a relatively small maximum distance from any point within the screen to the screen edge, the heat generated will be sufficient to dc-ice the screen. Initial tests indicate that the invention will function satisfactorily with screens having a maximum distance from any point in the scrccn to the edge in the order of 15mm or lcss. However, with further development, it is possible that the invention could be adapted successfully for application to screens having a larger maximum distance from any point to the screen edge. In this regard, it should be noted that window screens for cameras on vehicles are very small, being the size of a finger nail in some cases.

The actuator 28 may be an ultrasonic actuator and can be arranged to deflect the screen assembly in a lateral direction, as indicated by arrows X, parallel to the plane of the screen assembly. In the present embodiment, the actuator 28 is operatively connected between the tailgate panel 16, or some other component fixed to the support, and the outer frame 26 of the screen assembly 20. The actuator could be operatively connected directly to the screen 24. This would be necessary where the frame 26 is omitted.

The actuator 28 is connected to a power supply by means of a cable 30.

Operation of the actuator may be controlled automatically by a control system of the vehicle; or in response to a manual input from a user of the vehicle. Thus when ice is detected on the screen, for example by means of an obscuration sensor, and/or a low ambient temperature is detected, the actuator 28 is activated so that heat is generated in the seal 22 and conducts into the screen 24 to cause the ice to melt. The actuator 28 need be operated on'y for the time required to effectivdy dc-ice the screen.

1 0 The apparatus in accordance with the invention has the advantage that it is simple to instafl -even for use in remote locations such as the tailgate of a vehic'e -and is easy to operate. It has the further advantage that vibrating the screen 24 will tend to dislodge ice particles and/or water droplets from the screen 24 more quickly than would be the case in a system relying on heat alone. A frirther benefit is that the apparatus can be used to quickly dry the screen in the event it is washed by means of an external water jet or has become wet though environmental moisture, e.g. rain, humidity, water splash, etc. It should be noted also, that the apparatus according to the invention may be used in combination with a screen washer jet (similar to a windscreen washer jet) which is installed on the vehicle. In these scenarios, the vibration of the screen would in combination with the heating effect result in quick drying of the screen without the need for hot air blowers. This effect can be enhanced by the application of a hydrophobic coating to at least the exterior surface of the screen 24 to increase the size of the water droplets, thus increasing the ease with which they can be shaken off Where a window washer jet is fitted to the vehicle, this would be used to wash dirt off the window prior to the drying operation; or to clean the window after de-icing.

The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims. For example, the actuator 28 need not be an ultrasonic actuator. It will also be appreciated that the shape of the screen 24 can be varied as desired and could, for example, be circular rather than rectangular. Furthermore, whilst the invention has been described in relation to a screen for a camera on a vehicle, the principles described can be applied to any application where it is necessary to dc-ice or indeed to dc-mist a screen mounted to a support by means of an elastomeric seal, and where the dimensions of screen are such that the heat generated in the seal when the screen is vibrated heats the screen sufficiently to dc-ice or dc-mist the screen.

Thus the invention could be applied to camera screens for non-vehicle applications; or indeed to screens for other types of sensor where the screen is transparent to at least a desired range of electromagnetic radiation which may not be visible light, such as radio waves, microwaves, infrared radiation, ultraviolet radiation, X-rays, and gamma rays. For example, the invention could be adapted for use with a screen for a radar obstade detection system; while the seal material maybe doped to increase heat generation and/or conduction. The actuator may be switched on automatically with a heated rear window, or with front or rear windscreen wipers. The invention has the advantage that there is no requirement to apply metallic conductive coatings to the screen, which coatings might interfere with the transmission of electromagnetic radiation through the screen.

Claims

CLAIMS1. A method of dc-icing a screen mounted to a support by means of an elastomeric seal, thc method comprising vibrating the screen relative to the support so as to cause deformation of the seal such that internal friction in the seal generates heat which is conducted to the screen.

2. A method as claimed in claim 1, wherein the screen has a high ratio of perimeter to surface area.

3. A method as claimed in claim 1 or claim 2, wherein the method comprises vibrating the screen at high frequency and low amplitude.

4. A method as claimed in any one of the previous claims, wherein the method comprises vibrating the screen by means of an actuator.

5. A method as claimed in any one of the previous claims, wherein the method comprises vibrating the screen by means of an ultrasonic actuator.

6. A method as claimed in any one of the previous claims, wherein the screen is part of a screen assembly comprising an outer frame surrounding the screen.

7. A method as claimed in any one of the previous claims, wherein at least an outer edge region of the screen and a corresponding inner edge region of the support that are both engaged by the seal are substantially planar; and the method comprises vibrating the screen in a direction substantially parallel to the planar edge regions.

8. A method as claimed in any one of the previous claims, wherein the screen is substantially planar and the method comprises vibrating the screen in a direction substantially parallel to the plane of the screen.

9. A method as claimed in any one of the previous claims, wherein the screen is substantially transparent to at least a desired range of electromagnetic radiation.

10. A method as claimed in any one of the previous claims, wherein the screen is substantially transparent to visible light.

11. A method as claimed in any one of the previous claims, wherein the screen comprises a window for a camera mounted to a vehicle, such as a lane departure warning system camera.

12. A method as claimed in claim 11, in combination with use of a window washer jet mounted to the vehicle.

13. Apparatus for dc-icing a screen mounted to a support by means of an elastomeric seal, the apparatus comprising an actuator operatively connected with the screen for vibrating the screen relative to the support.

14. Apparatus as claimed in claim 13, wherein the apparatus is configured so that, in use, vibration of the screen causes deformation of the seal such that internal friction in the seal generates heat which is conducted to the screen.

15. Apparatus as claimed in claim 13 or claim 14, wherein the screen has a high ratio of perimeter to surface area.

16. Apparatus as claimed in any one of claims 13 to 15, wherein the actuator is configured to vibrate the screen at high frequency and low amplitude.

17. Apparatus as claimed in any one of claims 13 to 16, wherein the actuator is an ultrasonic actuator.

18. Apparatus as claimed in any one of claims 13 to 17, wherein the actuator is indirectly operatively connected with the screen.

19. Apparatus as claimed in any one of claims 13 to 18, wherein the screen is part of a screen assembly couipiising an outer frame surrounding the screen, the actuator being operatively connected with the outer frame.

20. Apparatus as claimed in any one of claims 13 to 19, wherein at least an outer edge region of the screen and a corresponding inner edge region of the support that are both engaged by the seal are substantially planar; and the actuator is configured to vibrate the screen in a direction substantially parallel to the planar edge regions.

2LApparatus as claimed in any one of claims 13 to 20, wherein the screen is substantially planar; and the actuator is configured to vibrate the screen in a direction substantially parallel to the plane of the screen.

22.Apparatusasclaimedinanyoneofclaims 13to21,whereinthescreenismadeof a material that is substantially transparent to at least a desired range of electromagnetic radiation.

23. Apparatus as claimed in any one of claims 13 to 22, wherein the screen is substantially transparent to visible light.

24. Apparatus as claimed in any onc of claims 13 to 23, whcrcin thc screen has a hydrophobic coating at least on its exterior surthee.

25. Apparatus as claimed in anyone of claims 13 to 24, wherein the screen comprises a window for a camera.

26. Apparatus as claimed in anyone of claims 13 to 25, wherein the screen comprises a window for a camera mounted to a vehicle, such as a lane departure warning system camera.

27. Apparatus as claimed in claim 26, wherein the vehicle comprises a washer jet for said jindov 28. A vehicle having a camera mounted in a camera housing, and a camera screen through which the camera is directed, the screen being mounted to a support by mcans of an clastomeric seal; thc vchiclc comprising apparatus for dc-icing tim camera screen as claimed in any one of claims 13 to 27.