JPH0687406A - Window glass heating system - Google Patents

Abstract

PURPOSE:To improve the accuracy of crack detecting with simple constitution, by making constitution, in which a first and a second electrode zone are arranged on both the ends of a resistant coating film; a current difference between the first and the second conductive wires of one respectively, connected the given places of the first and the second electrode zones is detected; and feed is stopped when the current difference has a given value or more. CONSTITUTION:A window glass 2 is provided with a heating system for defrosting, first and second electrode zones 3 and 4, and a resistant film 5. A pair of first conductive wires 61 and 62 and second conductive wires 71 and 72 are connected to both the ends of the first and the second electrode zones 3 and 4 respectively. When a crack (a) occurs, part or the whole of the second electrode zone 4 is disconnected, consequently current 11 is reduced but current 12 is hardly changed. Consequently the current difference between currents 11 and 12 become large to be detected by a current detector 9. When a detected value becomes a given level or more, feed to the resistant film 5 is stopped by a controller 8, and even a tiny crack can be accurately detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wind glass heating device for defrosting and defrosting a vehicle wind glass, and for defrosting and defrosting.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 61-27741 discloses a resistive coating provided on a window glass, a pair of electrode strips connected to two opposing sides of the resistive coating, and a pair of electrode strips. In a window glass heating device provided with a power supply circuit for controlling power supply of the device, it is disclosed that a change in the resistance value of the resistive coating is detected by a voltage change between the pair of electrode bands to detect a crack in the window glass. .

Japanese Patent Application Laid-Open No. 4-4684 filed by the applicant
No. 7, as shown in FIG. 3, first conductive lines 61, 62 connected to the pair of electrode bands 3, second conductive lines 71, 72 connected to the electrode band 4, and first conductive lines. In a window glass heating device including a pair 61, 62 and a power supply circuit for controlling energization between the second conductive wire pairs 71, 72, a first conductive wire pair 61, 62 (or a second conductive wire pair 71, 72). It is disclosed that the crack of the wind glass is detected by detecting the current difference between the two.

[0004]

However, in the prior art disclosed in the former publication, there is a detection error due to manufacturing variations in the resistance value of the resistive film, and therefore it is necessary to slow down the detection sensitivity. If the change in resistance value of the resistive coating due to cracking is as small as 20% or less, there is a problem that detection is difficult.

In the prior art disclosed in the latter publication, a highly accurate crack detection can be realized because the detection error due to the manufacturing variation of the resistance value of the resistive film can be offset.
However, as shown in FIG. 3, the resistive coating 5 including the electrode strips 4
The peripheral crack a is difficult to detect due to the current difference between the first conductive wires 61 and 62, and the peripheral crack a around the resistive coating 5 including the electrode strip 3 is difficult to detect due to the current difference between the second conductive wires 71 and 72. Therefore, in order to detect cracks related to damage to the electrode strips 3 and 4, the current difference between the first conductive wires 61 and 62 and the second conductive wire 7 are detected.
Both the current difference of 1 and 72 must be detected, and there is a problem that the device configuration becomes complicated.

The damage of the first electrode band 3 and the second electrode band 4 causes local resistance heating and generation of sparks due to the high applied voltage, and is compared with the partial damage of the resistive film 5. The need for detection is extremely high. The present invention has been made in view of the above problems, and an object of the present invention is to provide a wind glass heating device capable of highly accurate crack detection with a simple device configuration.

The present invention prevents the damage of the electrode strip due to cracking,
An object of the present invention is to provide a wind glass heating device that can be detected with a simple device configuration.

[0008]

According to another aspect of the present invention, there is provided a window glass heating device, comprising: a first electrode strip and a second electrode strip disposed on a wind glass so as to face each other; A resistive coating formed on the window glass, a plurality of first conductive wires each one end of which is connected to a predetermined position of the first electrode strip, and a plurality of one end ones of which are connected to a predetermined position of the second electrode strip. A second conductive wire, and a power supply circuit for controlling energization between each of the first conductive wires and each of the second conductive wires, a window glass heating device comprising: A current difference detecting means for detecting a difference between the currents applied to the second conductive wire pair, and a power supply stopping means for stopping power supply to the resistive film when the current difference detected by the current difference detecting means is equal to or higher than a predetermined level. It is characterized by having and.

[0009]

In the power supply circuit, the plurality of first conductive lines, the first electrode strip, the resistive coating, the second electrode strip, and the plurality of second conductive lines are energized in this order. A current difference between one of the plurality of first conductive lines connected to the predetermined position of the first electrode strip and one of the plurality of second conductive lines connected to the predetermined position of the second electrode strip causes a crack. The current difference detecting means detects the current difference, and the power supply stopping means stops the power supply to the resistive film when the current difference is equal to or higher than a predetermined level.

[0010]

As described above, the window glass heating device of the present invention has the low resistance first and second ends on both ends of the resistive coating.
One of a plurality of first conductive lines provided with electrode strips and connected to a predetermined position of the first electrode strip, and one of a plurality of second conductive lines connected to a predetermined position of the second electrode strip Since the structure for stopping the power supply to the resistive film when the current difference of is above a predetermined level is adopted, it is possible to realize a wind glass heating device capable of highly accurate crack detection with a simple device structure. .

That is, according to the present invention, the crack is not caused by the change in the entire current supplied to the resistive film but by the increase in the difference between a part of the current flowing into the resistive film and a part of the current flowing out of the resistive film. Since the change in the voltage applied to the resistive film and the variation in the resistance value of the resistive film cause the same change in both the inflow current and the outflow current, the fluctuation in the current difference is small and the accuracy is improved. Can be planned. For example, if there is no crack and the current difference is set to almost 0, even if the applied voltage changes and the resistance value of the resistive coating varies, the current difference remains almost 0 and high-precision detection is possible. It will be possible.

Next, according to the present invention, when either of the electrode strips is cracked and the resistive coating itself is only slightly cracked, the current difference between a pair of conductive wires individually connected to both electrode strips is calculated. Since the detection is performed, it is possible to obtain an excellent effect that the detection can be performed with high accuracy by using only one current difference detection unit.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A wind glass heating apparatus of the present invention will be described with reference to FIG. This window glass heating device heats a window glass 2 which is a laminated glass composed of two plate glasses to remove defrost, and the like. The first electrode band 3 and the second electrode band disposed on the window glass 2 are used. 4, the resistive coating 5, a pair of first conductive wires 61 and 62 having one ends connected to both ends of the first electrode strip 3, and a pair of second conductive wires having one end connected to both ends of the second electrode strip 4. A controller (power supply stopping means in the present invention) 8 for controlling the energization between the wires 71, 72 and the first conductive wires 61, 62 and the second conductive wires 71, 72.
And a current detector (current difference detecting means in the present invention) 9. The controller 8 and the current detector 9 form a power supply circuit according to the present invention.

The first and second electrode strips 3 and 4 are arranged by printing or firing a conductive paste such as Ag paste to a width of about 1 cm on one mating surface, and the first electrode strip 3 is a window glass. 2 is arranged parallel to the lower side about 1 cm away from the lower side, and the second electrode strip 4 is arranged substantially parallel to each side apart from the remaining 3 sides of the window glass 2. Both ends of the second electrode strips 3 and 4 reach the lower side of the window glass 2.

The resistive coating 5 is formed by sputtering or vacuum deposition of indium tin oxide (ITO) or the like, and the upper and lower sides of the resistive coating 5 are the first and second central portions of the electrode strip 3 and the second and third electrodes. The electrode strips 4 are individually connected to the central portion of the upper side. The first conductive line 61 connects one end of the first electrode strip 3 to the low level output end of the power supply circuit 8,
The first conductive wire 62 is connected to the other end of the first electrode strip 3 and the power supply circuit 8
Connected to the low level output terminal of the
One end of the electrode strip 4 is connected to the high level output end of the power supply circuit 8, and the second conductive line 72 connects the other end of the second electrode strip 4 to the high level output end of the power supply circuit 8. . The first and second conductive wires 61, 62, 71, 72 are made of ordinary insulated cables.

The current detector 9 includes a first conductive wire 61 and a second conductive wire 61.
A magnetic ring with a gap (not shown) through which the conductive wire 71 penetrates, a magnetic semiconductor current sensor (not shown) interposed in the gap of the magnetic ring, and an amplifier (amplifier) that amplifies the output voltage of this sensor. The current I2 of the first conductive line 61 and the second conductive line 71 are provided at the output end of the sensor.
A DC signal voltage that is proportional to the difference between the current I1 and the current I1 is generated.
This DC signal voltage is amplified by the amplifier and transmitted to the input terminal of the controller 8. Of course, other types of current detectors 9 can be adopted.

As shown in FIG. 2, the controller 8 includes a comparator 82, an OR circuit 84, a current amplification transistor 86,
A high-voltage power transistor 89, a high-voltage power source E of DC 200V, resistors 83, 85, 87, 88 are provided, and 12V is supplied as a power source for control. The operation of this device will be described below. However, the electrode strips 3, 4, each conductive wire 61,
The resistances 62, 71, 72 are sufficiently lower than that of the resistive coating 5, and as a result, the magnitudes of the currents flowing through the conductive wires 61, 62, 71, 72 are equal to each other when there is no crack. . In addition, a power supply voltage + 12V for control is applied to the current detector 9 and the controller 8 and is in a standby state.

When the operation switch 10 is closed, one of the inputs of the OR circuit 84 becomes low level due to the voltage drop of the resistor 83. In this case, since the current difference between the conductive lines 61 and 71 is almost 0 as described above, the current detector 9 is connected to the comparator 82.
The output DC signal voltage Vi output to
The comparator 82 compares the predetermined reference voltage Vref with the DC signal voltage Vi. In this case, since Vref> Vi, a low level is input to the OR circuit 84. Therefore, the two-input voltage of the OR circuit 84 becomes low level, and the OR circuit 84 turns off the current amplification transistor 86 through the base current limiting resistor 85. Current amplification transistor 86
Constitutes a grounded-emitter amplifier together with the collector resistor 87, the output voltage of which becomes a high level and the high voltage power transistor 89 through the base current limiting resistor 88.
Turn on. The emitter of the transistor 89 is connected to the low level terminal VL of the high voltage power source E, the collector of the transistor 89 is connected to the first conductive lines 61 and 62, and the high level terminal VH of the high voltage power source E is the second conductive line 71. It is connected to 72. As a result, when the transistor 89 is turned on, the resistive coating 5 is energized, and the defrosting or defrosting of the window glass 2, defrosting, and defrosting are performed.

When the window glass 2 is cracked, the resistance value of the resistive coating 5 changes and the current balance of the conductive wires 61, 62, 71, 72 also changes, and the conductive wires 61, 71 or 62. , 72, the crack can be detected. That is, when the crack a occurs as shown in FIG. 1, the crack a cuts part or all of the second electrode strip 4, and as a result, the current I1 decreases, the current I4 increases, and the current I4 increases.
The changes in 2 and I4 are almost negligible. As a result, the current difference I
1-I2 (may be other current difference) becomes large, the comparator 82 outputs a high level, and the OR circuit 84
Outputs a high level voltage, the transistor 86 is turned on, the power transistor 89 is turned off, and the power supply to the resistive film 5 is cut off. Of course, the same applies when a part or all of the first electrode strip 3 is blocked by the crack b.

In this embodiment, each conductive wire 61, 6
Although 2, 71, and 72 are connected to both ends of the first electrode strip 3 and the second electrode strip 4, the invention is not limited thereto. For example, the first conductive line 61 is provided on the first quarter of the first electrode strip 3 from the left to the first
The conductive wire 62 is a 3/4 portion from the left of the first electrode strip 3, the second conductive wire 71 is a ¼ portion from the left of the second electrode strip 4,
If the second conductive line 72 is connected to the left 3/4 portion of the second electrode strip 4, the resistance loss of the first electrode strip 3 and the second electrode strip 4 can be reduced.

Also, three or more conductive wires can be individually connected to the electrode strips. It is preferable that the two types of currents detected by the current detector 9 are substantially equal to each other when no crack occurs. In this case, the current difference becomes 0 in the normal state, so that the current difference remains 0 regardless of the voltage change or the resistance value change of the resistive film 5, so that the accuracy can be improved.

However, this embodiment can have a predetermined current difference ΔI when the two kinds of current differences detected by the current detector 9 do not cause cracks. In this case, this current difference ΔI is caused by voltage fluctuations or fluctuations in the resistance value of the resistive coating 5.
However, the first electrode strip 3 or the second electrode strip 3
The effect that the disconnection of the electrode strip 4 can be detected can be obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the controller of FIG.

FIG. 3 is a block circuit diagram of a conventional window glass heating device.

[Explanation of symbols]

 2 Wind glass 3 First electrode band 4 Second electrode band 5 Resistive film 8 Controller 9 Current detector 61, 62 First conductive wire 71, 72 Second conductive wire

Claims (1)

[Claims] 1. A first electrode strip and a second electrode strip disposed to face each other on the windshield, a resistive coating formed on the windshield between the two electrode strips, and A plurality of first conductive wires each having one end connected to a predetermined position of one electrode strip, a plurality of second conductive wires having one end connected to a predetermined position of the second electrode strip, and each first conductive wire And a power supply circuit for controlling energization between each of the second conductive wires, the difference in energizing current between one of the first conductive wires and one of the second conductive wire pairs is detected. And a power supply stopping means for stopping power supply to the resistive film when the current difference detected by the current difference detecting means is equal to or higher than a predetermined level.