Heaters for automotive mirrors and rearview assemblies using the same

• US 8,344,288 B2
• Filed: 01/12/2010
• Issued: 01/01/2013
• Est. Priority Date: 01/12/2010
• Status: Active Grant

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Door, Michael J., Myers, Craig R.
• Primary Examiner(s): Jackson, Jr., Jerome
• Application Number:
  US12/686,019
• Publication Number:
  US 20110168687A1
• Time in Patent Office: 1,085 Days
• Field of Search: 219/219
• US Class Current: 219/219
• CPC Class Codes: B60R 1/0602 comprising means for cleaning or deicing
• CPC Class Codes: H05B 3/845 specially adapted for reflecting surfaces, e.g. bathroom - or rearview mirrors

Abstract

A vehicular rearview assembly with a heating element. The heating element is affixed behind and in thermal communication with the mirror element of the assembly. The heating element includes a plurality of heating zones that operate in alternation according to a pre-determined time-sequence. A peripheral area of the mirror element is heated up to at least as high a temperature as an inner area of the mirror element. Switching the heating zones on and off so as to have only one heating zone on at a time is determined by a controlling circuitry at least a portion of which may be separated from the assembly and disposed in a different part of the vehicle.

Claims

1. An exterior automotive rearview assembly for use in association with a vehicle, the assembly comprising:

a mirror element adapted for use with the exterior automotive rearview mirror assembly and having a perimeter, said mirror element being subject to at least one of formation of ice and condensation of water vapor on a surface thereof during a normal operation of said assembly, said mirror element having an inner area and a peripheral area defining a first band around the perimeter and substantially enclosing the inner area;

a heating element located behind said mirror element with respect to a viewer, the heating element comprising peripheral and inner heating zones, said peripheral and inner heating zones defined by respectively corresponding electrical trace patterns, said peripheral and inner heating zones respectively corresponding to the peripheral and inner areas of said mirror element, each heating zone being in thermal contact with a corresponding area of the mirror element, said peripheral heating zone arranged in a substantially surrounding relationship with respect to said inner heating zone; and

a processor electrically connected with the heating element, the processor configured to switch a current flow among the heating zones to cause the heating element to heat the peripheral area to a first temperature and the inner area to a second temperature to effectuate spatially uneven dissipation of heat over a surface of the mirror element by one or more of (i) heating said peripheral area prior to heating said inner area and (ii) heating said inner area to the second temperature that is lower that the first temperature.

2. An assembly according to claim 1, wherein said formation of ice and condensation of water vapor define an anchor region of the peripheral area of the mirror element, said anchor region remaining at a temperature of substantially zero degrees Centigrade at least until a remaining portion of the mirror has been fully defrosted under first defrosting conditions, said first defrosting conditions including (i) spatially even dissipation of heat over the surface of said mirror element or (ii) heating said mirror element starting from a central area and moving outwardly to the peripheral area.

3. An assembly according to claim 1, wherein said peripheral and inner heating zones are spatially non-overlapping.

4. An assembly according to claim 1, wherein the processor is further configured to switch the current flow among the heating zones so as to cause the heating element to change a temperature of the peripheral area while maintaining a temperature of the inner area.

5. An assembly according to claim 1, wherein the heating zones are configured to generate different heat outputs per unit area.

6. An assembly according to claim 1, further comprising a light source behind the heating element with respect to the viewer, said light source configured to provide visually-perceivable indicia representing operation of the vehicle, said heating element containing a light indicia area that is free of said trace pattern and is arranged in overlying registry with said light source such as to transmit light from said light source through said light indicia area towards the viewer.

7. An assembly according to claim 1, wherein the processor is configured to switch the current flow between the first and second heating zones so as to cause the heating element to vary temperatures of the peripheral and inner areas according to a method that comprises

measuring, with a plurality of temperature sensors, temperature values across a surface of the mirror element;

increasing a peripheral area temperature to a first value while maintaining an inner area temperature at a second value;

increasing a peripheral area temperature to a first maximum value and an inner area temperature to a second maximum value such as to effectuate uneven dissipation of heat across said mirror element; and

maintaining a peripheral area temperature at a first maintenance value and an inner area temperature at a second maintenance value,

wherein the first and second maintenance values are lower than the first and second maximum values and the first maximum value is at least as high as the second maximum value.

8. An assembly according to claim 1, wherein the mirror element includes at least one of an electrochromic element, a plurality of glass substrates, and a prismatic element.

16. An assembly according to claim 1, further comprising a reflective polarizer element in optical communication with said mirror element, the reflective polarizer element including an optically anisotropic polarizing birefringent plastic film configured to reflect light of one polarization and transmit light of orthogonal polarization.

17. An assembly according to claim 6, wherein said light source includes an LED and an at least one of an eccentric reflector and an elliptical reflector covering said LED to reflect light generated by said LED through said light indicia area.

9. An external automotive rearview mirror assembly for use by a viewer, the assembly comprising:

an electrochromic (EC) mirror element including contiguous peripheral and inner areas, said peripheral area circumscribing said inner area and disposed around a perimeter of said EC mirror element;

a heating element located behind the EC mirror element with respect to the viewer, the heating element comprising first, second, and third individually contiguous and non-overlapping heating zones, the first and second heating zones aggregately enclosing the third heating zone located in a substantially central portion of the heating element, the first and second zones being in thermal contact with the peripheral area of the mirror element, the third heating zone being in thermal contact with the inner area of the mirror element; and

electronic circuitry operably associated with a vehicle that is adapted to host said mirror assembly,

wherein each of the first, second, and third heating zones has a corresponding pair of terminal contacts through which each of said heating zones is connected to said electronic circuitry, and

wherein said first, second, and third heating zones are adapted to generate heat alternatively so as to effectuate uneven dissipation of heat over a surface of the mirror element and to heat the peripheral area to a first temperature and the inner area to the second temperature.

10. An assembly according to claim 9, wherein said electronic circuitry further comprises a processor electrically connected to the heating element, the processor configured to switch a flow of current generated by said electronic circuitry through the heating element among the heating zones to cause the heating element to vary temperatures of the peripheral and inner areas in a time-sequenced fashion such as to achieve, in operation of said assembly under freezing conditions, defrosting of about 80 percent of an area of the EC mirror element in no more than about 150 seconds at about 12 or 13 Volts direct current and inrush current of below 4 Amperes.

11. An assembly according to claim 9, wherein the heating zones are, aggregately, substantially co-extensive with the mirror element in a surface of the mirror element to which the heating element is affixed.

12. An assembly according to claim 9, further comprising a light source behind the heating element with respect to the viewer, said light source configured to provide visually-perceivable indicia representing operation of the vehicle, said heating element containing a light indicia area that is substantially optically unobstructed and is arranged in overlying registry with said light source such as to transmit light from said light source through said light indicia area towards the viewer.

13. An assembly according to claim 9, wherein a first heating zones is dimensioned to transfer heat only to the peripheral area and a second heating zone transfers heat only to the inner area.

14. An assembly according to claim 9, wherein said electronic circuitry further comprises

a processor electrically connected with the heating element and configured to switch a current flow among the heating zones in an alternating fashion to effectuate one or more of (i) heating said peripheral area prior to heating said inner area and (ii) heating said inner area to the second temperature that is lower than the first temperature.

15. An assembly according to claim 9, wherein the heating element further includes temperature sensors configured to measure, in real time, temperature values across a surface of the mirror element, and wherein the processor has a computer readable program code thereon, the computer readable code including program code for determining a time sequence of switching the flow of current among the heating zones on and off based on the input received from the temperature sensors such as to effectuate heating of the mirror element starting from the peripheral area towards the inner area.