NL1010073C2 - Heated window for road vehicle has homogenous coating of resistive material through which heating current is passed via several electrodes around periphery of window - Google Patents

Abstract

In previous heated windows of this type, current from the supply (2) flowed through the resistive layer between two horizontal electrodes across the top and bottom of the window (1), resulting in uneven distribution of heat. To alleviate this problem, the present system applies current via an addition three pairs of electrodes at intervals along the sides of the window.

Description

-1- 5

System for evenly heating windows.

The invention relates to a system for the uniform heating of windows, which, for example, is used in automobiles and which is provided with an integrated heating element in the form of a transparent homogeneous layer of electrically conductive resistance material.

Heated car rear windows are generally fitted with a spiral heating element, which is integrated into the window and which can be connected to voltage via a switch, in order to allow this element to emit heat. Such a construction is not suitable for electrically heating windscreens, because the driver's view would be obstructed too much by the presence of the metal heating coils.

For this reason, the electric heating elements for automotive windscreens are designed in the form of a very thin, evenly distributed, transparent metal coating, which is vapor-deposited, or which is applied by dip coating. This usually takes place between two of the glass layers from which such panes are built. The electrical energy is supplied to these windows by providing a conductor strip on the top and bottom of the window, across the full width of the window, which makes contact across the full width with the coating integrated in the window, in order to distribute the voltage connected to the conductor strips between the top and bottom of the coating.

35 Due to the trapezoidal shape of the pane, which is narrower at the top than below, a greater current density in the coating p10100 7 3 -2- than in the rest of the pane results in the upper two corner points of the pane and, consequently, a greater heat development. . Accordingly, a lower current density arises in the lower vertices, which results in a lower temperature in these vertices.

The present invention aims to solve this problem and will be described below with reference to some figures.

Figure 1 schematically shows a window with coating and provided with two conductor strips with 10 connected power supply unit, on which is graphically indicated the isoterm for a number of temperatures.

Figure 2 schematically shows an electric window heating system according to the present invention.

Figure 3 shows schematically a glass pane with heating system according to the invention, on which the isoterm for a number of temperatures is also graphically indicated.

As can be seen in figure 1, the higher current density creates an increased temperature in the top corners of the car window. The temperature differences 20 can be as much as twenty or more degrees compared to the rest of the glass pane. These temperature differences create mechanical stresses and give an unpleasant sight to the driver in case of condensation or ice.

In the window heating system according to the invention, a more uniform heating of the window is obtained, by also making one or more electrical connections on both sides of the window and connecting an electrical voltage here, which corresponds to the electrical voltage of the window. coating in the center of the window, at the height of the relevant connection point. To achieve this, a voltage converter is used, which, in addition to converting the voltage from the on-board network from, for example, 12 volts to the approximately 42 volts required to obtain sufficient current through the ultra-thin layer of resistance material, generates one or more additional voltages. , which are connected in the right places on the sides of the glass.

* 1010073 -3-

Since it is obvious to choose the voltage of the on-board network of usually 12 volts as one of the voltages to be connected, the choice of two or three connection points seems optimal. More connection points give a more even distribution of current in the corner points of the glass pane and, consequently, a more even temperature distribution.

In addition to the cause described above, temperature differences also arise from the heat conduction to the window frame rebate and the body of the vehicle in which the window pane is mounted, as well as from differences in the heat transfer to the air flowing past the window pane. For this reason too, the choice of two or three additional connection points on the sides of the glass, which reduce the temperature differences to about five degrees, proves to be a good choice.

Figure 2 schematically shows a window heating system with three connection points on each side of the window (1), whereby the inverter (2) has a total of five connection points on the window (1). In order to obtain a more even current distribution on the connection strips, two inverters per window can also be used, whereby these inverters can be concealed on both sides in the posts next to the window.

Figure 3 schematically shows what the temperature distribution looks like in a window heating system according to the invention. It can be clearly seen that a smoothing occurs and that, especially in the corners, a more even temperature distribution is created.

30 »1010073

Claims (4)

1. A system for uniformly electric heating of trapezoidal (car) windows, which are provided with a homogeneous coating of resistance material, characterized in that in addition to the connection of an electrical voltage to conductor strips, which are located on the long top and bottom of the window are electrically connected to the thin layer of resistance material, also electrical voltage is connected to one or more connection points, which are electrically connected to the thin layer of resistance material on both short sides of the glass pane. 15 A system for uniformly electrically heating trapezoidal panes according to claim 1, characterized in that the electrical voltage to be connected to each of the terminals on the short sides of the pane corresponds substantially to the electrical voltage i of the thin layer of resistance material in the center of: the glass pane at the relevant connection point. A system for uniformly electrically heating trapezoidal panes according to one or both of the preceding claim (s), characterized in that the electrical voltage (s) to be connected to each of the terminals on the short sides of the pane, as well as the voltage across the connecting strips on the long top and bottom of the glass pane, are generated by one or more voltage converters, which convert the electrical voltage from the on-board network into the electrical voltage required for each connection point. -i 1010073 -5- A system for the uniform electric heating of trapezoidal windows according to one or more of the preceding claim (s), characterized in that the number of connection points on the short sides of the window 5 is chosen such that the electrical voltage of the on-board network can be are used for at least one of the connection points on the short sides of the glass pane. p1010 0 7 3