JPH06227367A - Windowpane heater - Google Patents

Abstract

PURPOSE:To detect a minute breakdown in a conductive membrane as well as to detect each disconnection of an electrode and a conducting sleeve by connecting a detector, detecting a high frequency signal to be outputted from an oscillator, to those of remaining electrodes. CONSTITUTION:An alternating current signal to be outputted from an oscillator 5 is inputted into a conductive membrane 2 by two electrodes 3a and 3d, and most of it passes through elements 31 and 32 existing on the shortest distance. Accordingly, there is almost none of electric potential monitored by electrodes 3b, 3c by way of other elements 33 and 34. Consequently, there is no input signal in a transformer 22, and thereby output of a comparator (A) comes to '1' (normal). If the conductive membrane 2 is broken down, a signal is varied by a variation in an equivalent circuit of this 1 conductive membrane, and this variation is detected by way of the transformer 22, and when the electrode 3 and a conducting sleeve 4 are broken down, a drop in impedance is caused by a magnetic saturation phenomenon in each of two transformers 7 and 8, through which the signal is varied and detected by way of a condenser 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a window glass heating device.

[0002]

2. Description of the Related Art Conventionally, in a windowpane heating device, it has been known to detect a change in current flowing through the heating device for the purpose of detecting damage to a conductive film.
It has been proposed by. However, when cracks occur in the conductive film or conductive wire on the glass plate, it is difficult to detect minute damage, and mass production is required because it is necessary to balance the conductive film and the detection circuit individually. It was not suitable for industrial use, and when this device was mounted on an automobile, the circuit constant of the detection part was changed due to vibration and the like, and the reliability was insufficient.

[0003]

DISCLOSURE OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, that is, the damage detection capability is low, it is not suitable for industrial use requiring mass production, or it is not suitable for automobiles. It is intended to eliminate the lack of reliability for mounting.

[0004]

The present invention has been made to solve the above-mentioned problems, and two pairs of electrodes whose ends are separated from each other are arranged along opposite sides of a glass plate, and the electrodes are opposed to each other. Any one of an electric heating window glass having a conductive film formed between electrodes, a power supply circuit for supplying power to the conductive film via the electrode, an oscillation circuit, and the conductive film, the electrode and the power supply circuit. A detection circuit for detecting breakage, the detection circuit includes a high-frequency coil, and the oscillation circuit is connected to a negative electrode of the electrode and an electrode adjacent to the positive electrode facing the electrode, and the rest A window glass heating device, characterized in that the detection circuit for detecting a high-frequency signal output from the oscillation circuit is connected to the remaining electrodes so as to obtain the relative potential and the absolute potential of the electrodes. To do.

FIG. 1 is an overall view of the present invention, in which 1 is a glass plate, 2 is a conductive film, 3 is an electrode, 4 is a conductive band, 5 is an oscillation circuit, 6 is a detection circuit, 7 and 8 are transformers, Reference numerals 9 and 10 denote capacitors, and 11 denotes a battery.

In FIG. 1, A is an electrically heated window glass. As this electrically heated window glass, for example, a glass plate 1 and another glass plate are joined together via an intermediate film such as polyvinyl butyral to form a laminated glass. Things are used. The window glass of the present invention is used for various applications such as automobiles, ships, and aircrafts, but is preferably used for automobile windshields.

Two pairs of electrodes are arranged on the glass plate 1 so as to face each other along opposite sides. That is, the glass plate 1
The electrodes 3a and 3b are provided with their ends separated from each other on one of the opposite sides thereof, and the electrodes 3c and 3d are also provided with their ends separated from each other on the other opposite side. The electrodes 3a and 3c are opposed to each other, and the electrodes 3b and 3d are opposed to each other. At the other ends of the electrodes 3a and 3c,
Conductive bands 4a and 4b are connected to each other, and conductive bands 4c and 4d are similarly formed at the other ends of the electrodes 3c and 3d.
Are connected and formed.

On the surface of the glass plate 1, an electrode 3 and a conductive band 4 are formed by printing and firing a conductive paste such as Ag paste.
Are formed.

A conductive film 2 is formed between these electrodes 3 by sputtering or the like. The conductive film 2 is formed of at least one kind of film of metal oxide or metal having good conductivity, and preferably formed of a laminated body of a metal oxide film and a metal film. Furthermore, as a metal oxide film, Z with a thickness of 200Å to 600Å
nO, ZrO ₂ or the like is preferable, and the metal film is 50 Å ~
250 Å thick Ag, Au, Al, Cu or the like is preferable.

The conductive film 2 is connected to the battery 11 via the electrode 3, the conductive band 4, and the high frequency coils 7a, 7b, 8a and 8b, and is supplied with electric power. It is preferable that the high frequency coils 7a and 7b form a transformer 7, and the high frequency coils 8a and 8b form a transformer 8.

The transformers 7 and 8 prevent the signal output from the oscillating circuit 5 from being cut off and cause a loss. In order to prevent magnetic saturation due to a large current, the transformers 7 and 8 have a primary coil and a secondary coil. It has the same inductance by winding a filer.

The oscillation circuit 5 is connected to a conductive band 4a connected to the electrode 3a and a conductive band 4d connected to an electrode 3d adjacent to the electrode 3c facing the electrode 3a (in a position oblique to the electrode 3a). Has been done. Further, the detection circuit 6 is connected to the remaining conductive bands 4c and 4d.

FIG. 2 is a detailed view of the oscillation circuit 5 and the detection circuit 6, wherein 21 and 22 are transformers, 23, 24 and 25 are capacitors, and 26 is an equivalent circuit of the conductive film 2. The oscillating circuit 5 outputs a sine wave or a pulse wave at a frequency f ₀ , and the transformer 21 sets the potential of its output signal regardless of the potential of the oscillating circuit, and has a + -symmetrical waveform here. The capacitor 23 has a direct current cut so that it does not serve as a direct current bypass path for the battery 11.

Only a high frequency component between the electrodes 3b and 3c is taken out by a DC cut capacitor 24 and a transformer 22 for extracting a potential difference, and a band pass filter (hereinafter referred to as BPF) having a center frequency f _0. As shown in (A), only the signal output from the oscillation circuit 5 is taken out, excluding the high frequency component in which noise or the like is mixed. Since the signal is square-law detected, the power of f ₀ is converted into a DC value through the squaring circuit (A) and the integrating circuit (A). If the DC value is less than or equal to the reference value, it is determined by the comparison circuit (A) that gives "1".

On the other hand, the high frequency component between the electrode 3d and the ground is extracted by the capacitor 25, and B. P. After passing through F (B), the squaring circuit (B), and the integrating circuit (B), it is converted into a DC value. There is a comparison circuit (B) that becomes "1" if the DC value is equal to or greater than the reference value, and if the outputs of the two comparison circuits (A) and (B) are "1", it is determined to be normal. There is a NAND circuit that outputs "0". If the output of this NAND circuit is "1", it means that the conductive film 2 or a part of the conductive band 4 is damaged.

[0016]

The conductive film 2, the electrode 3 and the conductive band 4 of FIG. 1 have no damage and show a normal example. The equivalent circuit 26 of FIG.
It is shown in a circuit.

In the present invention, the AC signal output from the oscillation circuit 5 is input to the conductive film 2 by the electrodes 3a and 3d, and most of it passes through the elements 31 and 32 located on the shortest distance. Therefore, the electrodes 3 are passed through the elements 33 and 34.
There is almost no potential monitored in b, 3c. Therefore, the transformer 22 has no input signal, and the output of the comparison circuit (A) becomes "1".

On the other hand, the high frequency potential between the electrode 3d and the ground is 1/2 of the output of the transformer 21, is detected through the capacitor 25, the output of the comparison circuit (B) becomes "1", and the comparison circuit ( Two "1" s in the outputs of A) and (B)
Thus, the NAND output becomes "0", indicating that the conductive film 2, the electrode 3, and the conductive band 4 are normal.

In the present invention, the battery 11 supplies a direct current to the conductive film 2 via the transformers 7 and 8, but the transformers 7 and 8 function as high frequency coils to block the output signal of the oscillating circuit 5. The condensers 9 and 1
0 and battery 11 can be ignored. The capacitors 9 and 10 are provided to remove noise generated from the battery 11 and other electric components connected to the battery 11.

Since the transformers 7 and 8 can prevent magnetic saturation by supplying direct currents in opposite directions to the primary side and the secondary side, the function as an inductance is not lost even when a large current is passed.

FIG. 3A shows an example in which the conductive film 2 is damaged at the central portion, and FIG. 3B shows an equivalent circuit 27 of the conductive film 2. Although the electrodes 3a, 3b, 3c and 3d have a bridge structure, the output signal of the oscillating circuit 5 is the transformer 2 because the probability of achieving zero balance is extremely low.
2 (see FIG. 2), the output of the comparison circuit (A) becomes "0". On the other hand, the potential between potential 3d and ground is
Since it is the same as normal, it is detected by the condenser 25,
The output of the comparison circuit (B) becomes "1", and as a result, NAN
The output of the D circuit becomes "1", and the abnormality of the conductive film 2 is detected.

FIG. 4A shows an example in which the conductive film 2 is broken at a point distant from the central portion, and FIG.
The equivalent circuit 28 of the conductive film 2 is shown. In the equivalent circuit 28, the potential of the electrode 3c is intermediate between 3a and 3d, but the potential of the electrode 3b becomes a value close to that of the electrode 3a,
A potential is generated between 3b and 3c, and the abnormality of the conductive film 2 is detected in the same manner as in the example of FIG. 3 described above.

FIG. 5A shows an example in which the conductive band 4b is damaged, and FIG. 5B shows an equivalent circuit of the entire detection circuit. When the conductive band 4b is disconnected, direct current does not flow in the coil 8b of the transformer, so that the coil 8a is magnetically saturated and the impedance of the coil 8a is reduced.

Further, the current flowing through the electrode 3b is concentrated on the electrode 3a, and a double current flows through the coil 7a without losing the balance with the current of the coil 7b. This also causes magnetic saturation, and the coil 7a Impedance will decrease. The output of the oscillation circuit 5 is short-circuited by the coils 7a and 8a,
No signal flows through the capacitor 25, and the output of the NAND circuit becomes "1" to detect an abnormality.

As described above, when the conductive film 2 is damaged, the signal changes due to the change in the equivalent circuit of the conductive film, and the transformer 22
When the electrode 3 and the conductive band 4 are damaged, the impedance is lowered due to the magnetic saturation phenomenon of the transformers 7 and 8, whereby the signal is changed and the signal is detected via the capacitor 25. The present invention is thus a window glass heating device having an extremely excellent crack detector function.

[0026]

EXAMPLE In FIG. 1, a glass plate 1 is used as an automobile windshield in combination with other glass using polyvinyl butyral as an intermediate film.

The electrode 3 and the conductive band 4 each having a maximum width of 15 mm formed by printing and firing Ag paste with a thickness of about 10 μm are formed on the bonding surface of the glass plate 1 on the outside of the car of the laminated glass for windshields for automobiles. Has been formed. These electrodes 3
The conductive band 4 is arranged along the side of the glass plate 1, and the electrodes 3a and 3c and the electrodes 3b and 3d are arranged to face each other.

A conductive film 2 is formed between these electrodes 3 by sputtering, and the conductive film 2 is formed by stacking ZnO and Ag.

The length of each of the electrodes 3a and 3b is 50.
cm, the length of each of the electrodes 3c and 3d is 60 cm, the distance between the adjacent electrodes 3a and 3b and the adjacent electrodes 3c and 3d is 5 cm, and the distance between the opposing electrodes 3a and 3c and the opposing electrodes 3b and 3d is 69 cm. Is.

The battery 11 is 48V, the current flowing through the entire conductive film 2 is 12A, the self-inductance of the primary and secondary coils of the transformers 7 and 8 is 1mH, the self-resonant frequency is about 1.1MHz, and the mutual inductance. Is 1 mH. 0.22μ for capacitors 9 and 10
It is an F film capacitor.

The oscillation circuit 5 has a frequency of 500 KHz, a pulse wave with an amplitude of 12 V, a winding ratio of the transformer 21 of 1: 1, and the capacitor 23 is a 0.1 μF Mylar capacitor. The B / D / F center frequency of the detection circuit 6 is 500 KHz, the square circuit and the integration circuit are diode detections, the comparison circuit and the NAND circuit are ICs, the capacitors 24 and 25 are 0.1 μF Mylar capacitors, and the transformer 22 The winding ratio is 1: 1.

When the glass plate 1 was cracked at the center of the conductive film 2 as shown in FIG.
An error was detected by the circuit.

Similarly, when the glass plate 1 was cracked as shown in FIG.
Abnormality was detected by the D circuit.

[0034]

According to the present invention, it is possible to detect minute breakage of the conductive film 2 and also to detect disconnection of the electrode 3 and the conductive band 4. In addition, as for the breakage of the conductive film 2, in principle, two states are detected when the bridge circuit is unbalanced and when the bridge circuit is simply the shortest resistance.
It is extremely stable and suitable for mass production, and is used for detecting disconnection of the electrode 3 and the conductive band 4 by sharing the transformers 7 and 8 and the oscillation circuit 5 prepared for detecting the conductive film damage. It is an efficient system. Also,
As described above, it is suitable for mass production, and at the same time, it withstands minute changes in circuit constants, and is therefore useful for automobiles.

[Brief description of drawings]

FIG. 1 is an overall view showing an embodiment of the present invention.

FIG. 2 is a detailed diagram of an oscillator circuit 5 and a detection circuit 6 shown in FIG.

3A is a state diagram of the glass plate 1 in which the conductive film 2 of FIG. 1 is damaged in the central portion. (B): An equivalent circuit diagram of the conductive film 2 in FIG.

4A is a state diagram of the glass plate 1 in which the conductive film 2 of FIG. 1 is damaged in the vicinity of a corner. (B): An equivalent circuit diagram of the conductive film 2 in FIG.

5A is a state diagram of the glass plate 1 in which the conductive band 4b of FIG. 1 is cut. (B): An overall equivalent circuit diagram including an equivalent circuit of the conductive film 2 in FIG. 5 (a).

[Explanation of symbols]

A: Electric heating window glass 1: Glass plate 2: Conductive film 3: Electrode 4: Conductive band 5: Oscillation circuit 6: Detection circuit 7, 8, 21, 22: Transformer 9, 10, 23, 24, 25: Capacitor 11: Battery 26, 27, 28, 29: Equivalent circuit of conductive film 2, 31, 32, 33, 34, 35, 36, 37, 38: Element of equivalent circuit 26

Claims (3)

[Claims] 1. An electric heating window glass formed by disposing two pairs of electrodes whose ends are separated from each other along opposite sides of a glass plate, and forming a conductive film between the facing electrodes, and the electrode. A power supply circuit that supplies power to the conductive film, an oscillation circuit, and a detection circuit that detects damage to any of the conductive film, the electrodes, and the power supply circuit, and the detection circuit includes a high-frequency coil. , The oscillation circuit is connected to the negative electrode of the electrode and an electrode adjacent to the positive electrode facing the electrode, and is output from the oscillation circuit so as to obtain the relative potential and the absolute potential of the remaining electrodes. A window glass heating apparatus, wherein the detection circuit for detecting a high frequency signal is connected to the remaining electrodes. 2. The windowpane heating device according to claim 1, wherein the high-frequency coil constitutes a transformer that cancels magnetic saturation. 3. The detection circuit, wherein an input signal passes through a band pass filter whose center frequency is the same frequency as the frequency output from the oscillation circuit, a square circuit, and an integration circuit. The windowpane heating device according to claim 1 or 2, further comprising a comparison circuit for comparing with the value.