JPH07309128A - Windshield heating device - Google Patents

Abstract

PURPOSE:To provide a windshield heating device capable of detecting fine cracks of a windshield of an electric vehicle by improving the accuracy of detection of a current sensor of the magnetic balance type, and reducing the cost of the product by using only one current sensor. CONSTITUTION:A current sensor 25 of magnetic balance type to detect the detected value where the difference between the first positive side current value flowing a first positive side conductive wire 21 and a first negative conductive wire 23, and the difference between the second positive side current value flowing a second negative side conductive wire 22 and the second negative side current value flowing a second negative side conductive wire 24 are added is provided in a power feeding circuit 8 of a conductive coating 7. The detected value of the current sensor 25 is compared with the reference value taking into account the product error by a comparative circuit 31, and when thc detected value is not less than the reference value, the energization of the conductive film 7 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a windshield heating device provided with a conductive coating for defrosting and defrosting a windshield, and more particularly to a crack detecting circuit for accurately detecting cracks in the conductive coating. It is related to the equipped windshield heating device.

[0002]

2. Description of the Related Art Conventionally, for example, a positive electrode and a negative electrode are provided along two sides facing a mating surface of a windshield of an automobile, and a conductive film is provided between the positive electrode and the negative electrode. Forming a positive side conductive wire, a negative side conductive wire,
A heated windshield (windshield heating device) for automobiles is known that defrosts and thaws the windshield by Joule heat generated by energizing a conductive film through a positive electrode and a negative electrode.

However, if a crack occurs in the windshield for some reason while the conductive film is being energized, the current concentrates on the conductive film that hits the cracked portion, sparks fly, and the conductivity of this portion is reduced. There was a problem that the conductive coating film locally generated heat than the conductive coating film at other locations.

Therefore, for the purpose of solving such a problem, conventionally, a windshield heating device 100 as shown in FIG. 5 has been proposed (Japanese Patent Laid-Open No. 4-4684).
(See Japanese Patent No. 7). This windshield heating device 100
Is a conductive film 1 formed on the windshield 101.
02, a positive electrode 103 is provided at one end of the conductive film 102.
The negative electrode 104 is provided at the other end of the positive voltage source 115 and the positive and negative electrodes 103 and 104 to connect the two positive side conductive wires 10 to each other.
5, 106 and two negative side conductive lines 107, 108 are connected.

The electric conduction control circuit 109 for the conductive film 102 has a magnetic balance type current sensor 111 for detecting the difference between the current values flowing through the two positive side conductive wires 105, 106.
Further, a magnetic balance type current sensor 112 for detecting a difference between current values flowing through the two negative side conductive lines 107 and 108 is installed.

The control circuit 11 of the energization control circuit 109
In No. 3, when the output voltage corresponding to the difference between the current values from the current sensors 111 and 112 increases above the threshold value (reference value), the relay 114 is opened to stop energizing the conductive film 102. The generation of sparks of the conductive coating 102 that hits the cracked portions of the windshield 101 is prevented, and local heat generation is prevented.

[0007]

However, in the conventional windshield heating apparatus 100, the detection accuracy of the magnetic balance type current sensors 111 and 112 is poor, so that if the current value applied to the conductive coating 102 is small, the window is not generated. It was very difficult to detect cracks in the shield 101.

In the conventional windshield heating apparatus 100, when the windshield 101 is not cracked, the current sensors 111 and 112 each output 0 A from the following equations (1) and (2). .

[Formula 1] Ik1 = i105 + i106

[Equation 2] Ik2 = i107 + i108

The reference value for judging cracks in the windshield 101 should ideally be as close as possible to ± 0 A so that even minute cracks can be detected. However, the reference value of the windshield 101 and the conductive film 102 should be as close as possible. Manufacturing error, positive side conductive lines 105, 106 and negative side conductive lines 107, 108,
It is necessary to set a value that will not be mistakenly determined to be cracked due to an error in the resistance value of the. Therefore, the conventional windshield heating device 100 is the windshield 1
The standard value for determining 01 cracking is set to ± 1.5A.

Then, a minute crack is generated in the windshield 101, i105 = 5A, i106 = 4A, i10.
When 7 = 5A and i108 = 4A, the current sensor 11
The detection currents of 1 and 112 are Ik1 = 1A and Ik2 = 1A.
Therefore, if the threshold value (reference value) of the control unit 113 is ± 1.5 A, it cannot be determined that the windshield 101 is cracked. That is, in the conventional windshield heating device 100, the windshield 101
However, there is a problem in that the detection accuracy of the minute cracks is poor.

The conventional windshield heating device 1
In 00, the two current sensors 111 and 112 detect cracks in the windshield 101, which causes an increase in product cost.

A first object of the present invention is to provide a windshield heating device capable of improving the detection accuracy of the current detecting means and detecting minute cracks in the windshield. The second object of the present invention is to
It is an object of the present invention to provide a windshield heating device capable of reducing the product cost by using one magnetic balance type current detecting means.

[0013]

According to a first aspect of the present invention, there is provided a conductive coating formed on a windshield, a plurality of positive electrodes connected to one end of the conductive coating, and a plurality of positive electrodes of the positive electrodes. A plurality of negative electrodes arranged facing each other and connected to the other end of the conductive coating, a positive side conductive wire connected to at least one positive electrode of the plurality of positive electrodes, and a plurality of the plurality of positive electrodes. Among the negative electrodes, a negative-side conductive wire connected to at least one negative electrode arranged at a position symmetrical to the at least one positive electrode is provided, and the negative side conductive wire is interposed between the plurality of positive electrodes and the plurality of negative electrodes. And a conduction control circuit for controlling conduction of the conductive film, wherein the conduction control circuit has a positive side current value flowing through the positive side conductive wire and a negative side flowing through the negative side conductive wire. Detects by doubling the difference with the side current value A technical means including one magnetic balance type current detecting means and an energization stopping means for stopping energization to the conductive film when the detection value detected by the current detecting means is equal to or larger than a reference value is adopted. .

According to a second aspect of the present invention, a conductive coating formed on the windshield, a plurality of positive electrodes connected to one end of the conductive coating, and a plurality of positive electrodes arranged facing each other. A plurality of negative electrodes connected to the other end of the conductive film, and first and second positive electrodes connected to each of at least two first and second positive electrodes of the plurality of positive electrodes. Of the plurality of negative electrodes, the side conductive wire is connected to each of at least two first and second negative electrodes arranged symmetrically to each of the first and second positive electrodes. A windshield heating device having first and second negative-side conductive wires, comprising: an energization control circuit that energizes and controls the conductive coating through the plurality of positive electrodes and the plurality of negative electrodes. The energization control circuit includes a first positive-side current flowing through the first positive-side conductive wire. And a first negative-side current value flowing through the first negative-side conductive wire, and a second positive-side current value flowing through the second positive-side conductive wire and the second negative-side conductive wire. One magnetic balance type current detecting means for detecting by adding the difference with the flowing second negative side current value, and to the conductive film when the detected value detected by this current detecting means is equal to or more than a reference value. The technical means including an energization stopping means for stopping the energization of is adopted.

According to a third aspect of the present invention, there is provided a conductive coating formed on the windshield, a plurality of positive electrodes connected to one end of the conductive coating, and the plurality of positive electrodes arranged to face the positive electrode. A plurality of negative electrodes connected to the other end of the conductive coating, and at least two first electrodes of the plurality of positive electrodes,
First and second positive side conductive lines connected to each of the second positive electrodes, and first connected to each of at least two first and second negative electrodes of the plurality of negative electrodes. A windshield heating device having a second negative-side conductive wire and including an energization control circuit for energizing the conductive film through the plurality of positive electrodes and the plurality of negative electrodes, The energization control circuit detects a first positive-side current value flowing through the first positive-side conductive wire, a first positive-side shunt resistor, and a second positive-side current value flowing through the second positive-side conductive wire. A second positive-side shunt resistor that detects a first negative-side shunt resistance that detects a first negative-side current value flowing through the first negative-side conductive wire,
And current detecting means having a second negative side shunt resistance for detecting a second negative side current value flowing through the second negative side conductive wire, and a first positive side detected by the first positive side shunt resistance. Side current value and the first negative side shunt resistance detected by the first
And a difference between a second positive side current value detected by the second positive side shunt resistor and a second negative side current value detected by the second negative side shunt resistor. Was adopted, and a technical means comprising an energization stopping means for stopping energization to the conductive film when the operation value added by the operation means is equal to or larger than a reference value.

[0016]

According to the invention described in claim 1, when the conductive coating is energized by the energization control circuit through the plurality of positive electrodes and the plurality of negative electrodes, the windshield is heated and the defrosting of the windshield and The ice is thawed. At this time,
One magnetic balance type current detection means connects to a positive side current value flowing through a positive side conductive wire connected to at least one positive electrode of the plurality of positive electrodes, and to at least one negative electrode of the plurality of negative electrodes. A detection value obtained by doubling the difference between the negative side current values flowing through the negative side conducting wire is detected. That is, the current detecting means has twice the detection accuracy of cracks in the windshield as compared with the conventional magnetic balance type current sensor that simply detects the difference between the positive side current value and the negative side current value.

According to the second aspect of the present invention, when the conductive film is energized by the energization control circuit through the plurality of positive electrodes and the plurality of negative electrodes, the windshield is heated and defrosting of the windshield is performed. The ice is thawed. At this time, the one magnetic balance type current detection means causes the first positive side current value flowing through the first positive side conductive wire connected to the first positive electrode of the plurality of positive electrodes and the plurality of negative side current values. A difference between a first negative-side current value flowing through a first negative-side conductive wire connected to the first negative electrode of the electrodes and a second negative electrode connected to a second positive electrode of the plurality of positive electrodes. A difference between a second positive side current value flowing through the positive side conductive wire and a second negative side current value flowing through the second negative side conductive wire connected to the second negative electrode of the plurality of negative electrodes. The added detection value is detected. That is, the current detecting means has twice the detection accuracy of cracks in the windshield as compared with the conventional magnetic balance type current sensor that simply detects the difference between the positive side current value and the negative side current value.

According to the third aspect of the present invention, when the conductive film is energized by the energization control circuit through the plurality of positive electrodes and the plurality of negative electrodes, the windshield is heated and defrosting of the windshield is performed. The ice is thawed. At this time, the first and second positive-side shunt resistors flow through the first and second positive-side conductive wires connected to each of at least two first and second positive electrodes of the plurality of positive electrodes. The first and second positive side current values are detected. Further, the first and second negative-side shunt resistors cause the first and second negative-side conductive wires connected to each of at least two first and second negative electrodes of the plurality of negative electrodes to flow through the first and second negative-side conductive wires. The first and second negative side current values are detected. The first and second positive side shunt resistors and the first and second
The second negative-side shunt resistor is superior to the conventional magnetic balance type current sensor in detection accuracy of cracks in the windshield. The difference between the first positive-side current value detected by the first positive-side shunt resistor and the first negative-side current value detected by the first negative-side shunt resistor and the second positive value are calculated by the calculating means. The difference between the second positive side current value detected by the side shunt resistance and the second negative side current value detected by the second negative side shunt resistance is added and the calculated value is output.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a windshield heating apparatus of the present invention will be described based on a plurality of embodiments shown in the drawings.

[Structure of First Embodiment] FIG. 1 shows a first embodiment of the present invention and is a view showing a windshield heating apparatus. This windshield heating device 1
For example, by heating the windshield 2 that constitutes the windshield of an electric vehicle, the windshield 2
Defrosting and de-icing are performed.

The windshield 2 is made of laminated glass in which two plate glasses are joined together via an intermediate film such as polyvinyl butyral. The first and second positive electrodes 3, 4 and the first and second positive electrodes 3 and 4 formed by printing or firing a conductive paste such as a silver paste on one mating surface of the two plate glasses.
The second negative electrodes 5 and 6 are formed.

The first and second positive electrodes 3 and 4 are electrode strips arranged along the upper side of the windshield 2 and are independently provided. First and second negative electrodes 5, 6
Is an electrode strip disposed along the lower side of the windshield 2 so as to be arranged so as to face the first and second positive electrodes 3 and 4, and the first and second positive electrodes 3 are 4 are provided at symmetrical positions.

A trapezoidal conductive coating 7 is formed on the windshield 2 between the first and second positive electrodes 3 and 4 and the first and second negative electrodes 5 and 6 by sputtering or vapor deposition. Has been done. The conductive film 7 is formed by laminating a metal oxide layer having good conductivity and a metal layer. The metal oxide layer is preferably a ZnO or ZnO ₂ layer having a thickness of 200Å to 600Å, and the metal layer is preferably an Ag, Au, Al or Cu layer having a thickness of 50Å to 250Å. In addition, the conductive film 7 includes the first and second positive electrodes 3, 4 and the first,
It is connected to the power supply circuit 8 via the second negative electrodes 5 and 6.

The power supply circuit 8 is the energization control circuit of the present invention, and is composed of a high voltage power supply 9, a relay circuit 10, an auxiliary power supply 11, an operation lamp 12, an operation switch 13, a crack detection device 14 and the like. ing. High voltage power supply 9
Is a battery of, for example, 288V that supplies electric power to a traveling electric motor (not shown) of the electric vehicle. The relay circuit 10 includes a relay coil 15 whose energization is controlled by the crack detection device 14, and a relay switch 1 which supplies or stops supply of electric power from the high-voltage power supply 9 to the conductive film 7.
It consists of 6.

The auxiliary power supply 11 is, for example, a 12V battery that supplies electric power necessary for operating a lighting device such as a headlight mounted on an electric vehicle, various motors such as a wiper motor, and various meters such as a speedometer. is there. The auxiliary power supply 11 is connected to the crack detection device 14 via an ignition switch 17.

The operation lamp 12 is a display means whose energization is controlled by the crack detection device 14 so that it is turned on when the electrically conductive film 7 is energized. The operation switch 13 is a manual operation means for instructing to operate or stop the windshield heating device 1 by manual operation.

The crack detecting device 14 includes a first positive-side conductive wire 21, a second positive-side conductive wire 22, and a first negative-side conductive wire 2.
3, second negative side conductive wire 24, magnetic balance type current sensor 2
5 and the control circuit 26 and the like.

One end of the first positive-side conductive wire 21 is connected to the positive (+) side of the high-voltage power supply 9 via the positive-side conductive wire 27 and the relay switch 16, and the other end thereof is the first positive-side wire. It is connected to the end of the electrode 3. One end of the second positive-side conductive wire 22 is connected to the positive (+) side of the high-voltage power supply 9 via the positive-side conductive wire 27 and the relay switch 16, and the other end thereof is connected to the second positive electrode 4.
Is connected to the end of.

One end of the first negative-side conductive wire 23 is connected to the negative (−) side of the high-voltage power supply 9 via the negative-side conductive wire 28, and the other end thereof is the end of the first negative electrode 5. Connected to the department.
One end of the second negative-side conductive wire 24 is connected to the negative (−) side of the high-voltage power supply 9 through the negative-side conductive wire 28, and the other end thereof is connected to the end of the second negative electrode 6. Has been done.

The current sensor 25, which is the current detecting means of the present invention, comprises a square-shaped iron core 29, a winding (not shown) wound around the iron core 29, and the like.
A voltage is generated based on the magnetic flux generated according to the current value flowing through the first, second positive-side conductive wire 22, the first negative-side conductive wire 23, and the second negative-side conductive wire 24.

The first positive-side conductive wire 21 is inserted through the iron core 29 of the current sensor 25 from the front surface to the rear surface of the iron core 29 so that the current flows from the high voltage power source 9 to the first positive electrode 3. It is wired so as to flow toward it. In addition, the second positive-side conductive wire 22 is formed by connecting the inside of the iron core 29 of the current sensor 25 to the iron core 2
9 is wired from the rear surface to the front surface so that current flows from the high-voltage power supply 9 to the second positive electrode 4.

Then, the first negative side conductive wire 23 is inserted through the inside of the iron core 29 of the current sensor 25 from the rear surface to the front surface of the iron core 29 so that the current flows from the first negative electrode 5 to the high voltage power source 9
It is wired so that it flows toward. The second negative side conductive wire 24 is inserted through the iron core 29 of the current sensor 25 from the front surface to the rear surface of the iron core 29, and the current flows from the second negative electrode 6 toward the high-voltage power supply 9. Is wired as.

Therefore, in the current sensor 25, the first positive-side current value flowing through the first positive-side conductive wire 21 and the first negative-side conductive wire 23 flow in the direction opposite to the first positive-side conductive wire 21. First
Of the second positive side conductive wire 22 and the second positive side conductive wire 23 flowing in the opposite direction to the second positive side conductive wire 22. The difference from the second negative side current value will be detected.

The current sensor 25 detects the difference (Ik1) between the first positive side current value (i21) and the first negative side current value (-i23) and the second positive side current value (i22). And the difference (Ik2) between the second negative side current value (-i24) and the difference (detection value = generated voltage corresponding to Ik1 + Ik2) are output to the control circuit 26 via the signal line 30.

The control circuit 26 is an electronic control unit (computer) which operates when an operating voltage is applied from the auxiliary power source 11 via the ignition switch 17,
It is an energization control unit that includes a CPU, a RAM, a ROM, and the like. The control circuit 26 turns on the actuation lamp 12 when the actuation switch 13 is pressed, and energizes the relay coil 15 to energize the conductive film 7.

The control circuit 26, while the conductive film 7 is being energized, has a detection value (generated voltage of the current sensor 25 = output voltage of the current sensor 25) inputted from the current sensor 25 via the signal line 30 and a threshold value ( It is provided with a comparison circuit 31 as a comparison means or a determination means for comparing with a reference value = (reference voltage corresponding to ± 1.5 A).

The comparison circuit 31 is an energization stopping means of the present invention, and is a detection value (=) output from the current sensor 25.
The generated voltage corresponding to Ik1 + Ik2) is a reference value (± 1.
When it is smaller than the reference voltage corresponding to 5 A), it is determined that the windshield 2 is not cracked, and the energization of the relay coil 15 is continued.

Further, the comparison circuit 31 causes the windshield to detect when the detected value (= the generated voltage corresponding to Ik1 + Ik2) output from the current sensor 25 is equal to or greater than the reference value (reference voltage corresponding to ± 1.5 A). When it is judged that the crack has occurred in 2, the power supply to the conductive coating 7 is stopped and the power supply to the relay coil 15 is stopped.

[Operation of First Embodiment] Next, the operation of the windshield heating apparatus 1 of this embodiment will be briefly described with reference to FIG.

(When no crack is generated in the windshield 2) When the ignition switch 17 is turned on (turned on), an operating voltage is applied to the control circuit 26 of the crack detecting device 14 to enter the standby state. Here, when the operation switch 13 is turned on (closed), the control circuit 26 energizes and excites the relay coil 15, and the relay switch 16 is closed. Then, the high voltage power supply 9 is energized and the operation lamp 12 is turned on. Therefore, the first and second positive side conductive lines 21, 22 and the first and second negative side conductive lines 23,
The first and second positive side current values i21, i22 and the first and second negative side current values i23, i24 flow through 24.

As a result, between the first positive side electrode 21 and the second negative side electrode 24, and between the second positive side electrode 22 and the first side electrode 22.
A voltage VB (for example, 288 V) is applied between the negative electrode 23 and the negative electrode 23, and the conductive film 7 starts heating the windshield 2 to defrost and thaw the windshield 2. At the same time, the current sensor 25 wired as described above has the first and second positive-side conductive lines 21 and 22 and the first and second negative-side conductive lines 23 and 24 flowing through the first and second negative-side conductive lines 23 and 24. The detection value based on the magnetic flux that changes according to the positive current values i21, i22 and the first and second negative current values i23, i24 is output to the control circuit 26 via the signal line 30.

The first and second positive-side conductive lines 21 and 22 and the first and second negative-side conductive lines 23 and 24 flowing through the first and second negative-side conductive lines 23 and 24, respectively.
The positive side current values i21, i22 and the first and second negative side current values i23, i24 are calculated by the following equations 3 to 5.

## EQU3 ## Ik1 = i21 + (-i23)

[Equation 4] Ik2 = i22 + (-i24)

[Equation 5] Ik = Ik1 + Ik2

When the windshield 2 is not cracked and the windshield 2 is normal, the following equation (6) is established, so the output of the current sensor 25 is the detected value (0A). The generated voltage becomes 0 V).

I21 = i22 = i23 = i24

(When a crack is generated in the windshield 2) Here, in this embodiment, in the control circuit 26, the current sensor 25 detects a value equal to or higher than a reference value (reference voltage corresponding to ± 1.5 A). When the (generated voltage) is output, it is determined that a crack has occurred in the windshield 2. Then, when a current of 5 A flows through the conductive film 7 as expressed by the following formula 7 when the windshield 2 is not cracked, the windshield 2 is cracked.

## EQU00007 ## i21 = i22 = i23 = i24 = 5A

As a result, the overall resistance value of the conductive film 7 also increases, the current value supplied by the high-voltage power supply 9 decreases, and the first and second positive-side conductive wires 21 and 22 and the first and second positive-side conductive wires 21 and 22. The first and second positive side current values i21 and i22 and the first and second negative side current values i2 flowing through the second negative side conductive lines 23 and 24.
3, i24 also changes.

For example, i21 = 5A, i22 because a crack (crack) a has entered the windshield 2.
= 4A, i23 = 4A, i24 = 5A, the following formula 8 is obtained from the formulas 3 to 5 above.
The formula is

## EQU00008 ## Ik = i21 + (-i23) + i22 + (-i24) = 5A + (-4) A + 5A + (-4) A = + 2A

Therefore, as described above, the output voltage corresponding to the detected value of the current sensor 25 (generated voltage corresponding to + 2A = + 2A) becomes larger than the reference value (reference voltage corresponding to + 1.5A), and the windshield 2 It will be judged that a crack has occurred in the.

As described above, when the windshield 2 is cracked in the control circuit 26, the control circuit 2
When the judgment is made in 6, the energization of the relay coil 15 is stopped to demagnetize and the relay switch 16 is opened. This stops the energization of the conductive coating 7 and
The operation lamp 12 is turned off. Windshield 2
The operation lamp 12 may be made to blink when a crack is generated in the vehicle to notify the driver of the electric vehicle of the abnormality. In this case, a display means such as a buzzer may be used instead of the operation lamp 12.

[Effects of the First Embodiment] The resistance value of the conductive film 7 depends on the manufacturing error of the windshield 2 and the conductive film 7.
Each product differs due to an error in the resistance values of the first and second positive side conductive lines 21 and 22 and the first and second negative side conductive lines 23 and 24. Therefore, the comparison circuit 31 causes the conductive film 7, the first and second positive side conductive wires 21 due to the manufacturing error,
22 and the difference between the first positive side current value i21 and the first negative side current value i23 due to the error in the resistance values of the first and second negative side conductive wires 23 and 24, and the second positive side current value i22. In order to prevent the difference between the current value i and the second negative side current value i24 from being judged as a crack and stopping the energization of the conductive film 7, the reference value for judging a crack is set to be relatively large.

Therefore, in the conventional technique, it was possible to determine that the minute cracks in the windshield 2 were normal, but in this embodiment, the conventional technique (see FIG. 5).
Compared with, the detection accuracy of the current sensor 25 is improved. That is, the output value output from the current sensor 25 to the control circuit 26 via the signal line 30 can be increased.

Therefore, even a minute crack in the windshield 2 can be accurately determined, so that the crack detecting device 14 has high detection accuracy. Therefore, it is possible to stop the energization of the conductive coating 7 when a minute crack of the windshield 2 occurs, and thus it is possible to prevent the generation of a local spark or the generation of heat at the minute crack portion of the conductive coating 7. it can.

In this embodiment, since only one magnetic balance type current sensor 25 is used, the control circuit 2
Since the structure of the comparison circuit 31 of FIG. 6 is half that of the conventional technique, the structure of the control circuit 26 can be simplified, so that the effects of both reduction of product cost and improvement of detection accuracy are combined. Can have

Incidentally, the reference value of whether or not the windshield 2 is cracked is ideally closer to ± 0 A ideally, but the detection accuracy is further improved, but the windshield 2 and the conductive coating 7 Manufacturing error, the first and second positive side conductive lines 21, 22 and the first and second negative side conductive lines 23, 2
It is necessary to set a value that is not erroneously detected due to an error in the resistance value of 4 or the like.

[Second Embodiment] FIG. 2 shows a second embodiment of the present invention and is a view showing a windshield heating apparatus. The second positive side conductive wire 22 of this embodiment is wound twice from the back side to the front side of the iron core 29 of the current sensor 25, and then inserted through the iron core 29 from the rear surface to the front surface of the iron core 29. , Are wired so that current flows toward the second positive electrode 4.

The second negative side conductive wire 24 is double wound so as to rotate from the front surface to the back surface of the iron core 29 of the current sensor 25, and then is inserted through the iron core 29 from the front surface to the back surface of the iron core 29. And is wired so that current flows toward the high-voltage power supply 9. The first positive-side conductive wire 21 and the first negative-side conductive wire 23 are the iron core 29 of the current sensor 25.
It is connected to the conductive film 7 and the high-voltage power supply 9 without passing through the inside.

In this embodiment, the detected value Ik of the current sensor 25 is calculated by the above-mentioned formula 5, and is expressed by the following formula 9, so that it is calculated by the following formula 10.

[Equation 9] i21 + i22 = i23 + 24

Ik = 2 × {(i22) + (− i24)}

Therefore, in this embodiment, one magnetic balance type current sensor 25 is used for the second positive side conductive wire 2
The detection value obtained by doubling the difference between the second positive-side current value i22 flowing through 2 and the second negative-side current value i24 flowing through the second negative-side conductive line 24 is detected, and the crack of the windshield 2 is detected. Precision is doubled. If the second positive side conductive wire 22 and the second negative side conductive wire 24 are wound three times or more around the iron core 29 of the current sensor 25, the detection accuracy becomes three times or more.

[Third Embodiment] FIG. 3 shows a third embodiment of the present invention and is a view showing a windshield heating apparatus. The first positive-side conductive wire 21 of this embodiment is wound twice from the front surface to the back surface of the iron core 29 of the current sensor 25 and then inserted through the iron core 29 from the front surface to the back surface of the iron core 29. , Are wired so that a current flows toward the first positive electrode 3.

The first negative-side conductive wire 23 is wound twice from the back side to the front side of the iron core 29 of the current sensor 25 and then inserted through the iron core 29 from the back side to the front side. And is wired so that current flows toward the high-voltage power supply 9. The second positive-side conductive wire 22 and the second negative-side conductive wire 24 are connected to the iron core 29 of the current sensor 25.
It is connected to the conductive film 7 and the high-voltage power supply 9 without passing through the inside.

In this embodiment, the detection value Ik of the current sensor 25 is calculated by the following formula 11 as in the second embodiment.

Ik = 2 × {(i21) + (− i23)}

Therefore, in this embodiment, one magnetic balance type current sensor 25 is used for the first positive side conductive wire 2
The detection value obtained by doubling the difference between the first positive-side current value i21 flowing through 1 and the first negative-side current value i23 flowing through the first negative-side conductive wire 23 is detected, and the crack of the windshield 2 is detected. Precision is doubled. If the first positive-side conductive wire 21 and the first negative-side conductive wire 23 are wound three times or more around the iron core 29 of the current sensor 25, the detection accuracy becomes three times or more.

[Fourth Embodiment] FIG. 4 shows a fourth embodiment of the present invention and is a view showing a windshield heating apparatus. As the current detecting means of this embodiment, a first positive-side shunt resistor 41, which is superior to the conventional magnetic balance type current sensor in detection accuracy of cracks of the windshield,
The second positive side shunt resistor 42, the first negative side shunt resistor 43, and the second negative side shunt resistor 44 are used.

First and second positive side shunt resistors 41, 42
Is the first flowing through the first and second positive side conductive lines 21 and 22,
The second positive-side current values i21 and i22 are detected and an output voltage corresponding to the detected current value is output to the control circuit 26. Further, the first and second negative side shunt resistors 43 and 44 are connected to the first and second
The first and second negative side current values i23 and i24 flowing through the negative side conductive lines 23 and 24 are detected and an output voltage corresponding to the detected current value is output to the control circuit 26.

The control circuit 26 of this embodiment is the comparison circuit 3
1 and the arithmetic circuit 32 are built-in, and the signal lines 33 to 3
It is connected to the first and second positive side shunt resistors 41 and 42 and the first and second negative side shunt resistors 43 and 44 via 6. The arithmetic circuit 32 is the arithmetic means of the present invention, and the arithmetic value Ik is expressed by the following equations 12 to 14.
Is calculated.

[Equation 12] Ik1 = i21 + (-i23)

[Expression 13] Ik2 = i22 + (-i24)

[Equation 14] Ik = Ik1 + Ik2

Then, the comparison circuit 31 determines whether or not the windshield 2 is cracked, depending on whether or not the calculated value output from the calculation circuit 32 is equal to or larger than the reference value. As a result, it is possible to dramatically improve the accuracy of detecting cracks as compared with the conventional technique.

[Modification] In this embodiment, the high voltage power source 9 is used.
Although the switching means for controlling energization and de-energization of the conductive coating 7 with the conductive film 7 is constituted by the relay circuit 10, the switching means may be constituted by a semiconductor such as a transistor, a power MOS, or a solid state relay.

In this embodiment, a 288V battery was used as a power supply source for supplying power to the conductive film 7, but a 48V to 400V power supply may be practically used as a power supply source.

In this embodiment, one positive side conductive wire is connected to one positive electrode, but two or more positive side conductive wires may be connected to one positive electrode. Further, in this embodiment, one negative side conductive wire is connected to one negative electrode, but two or more negative side conductive wires may be connected to one negative electrode.

In this embodiment, the present invention is applied to the windshield heating device 1 for heating the windshield of an electric vehicle, but the present invention is also applied to a windshield heating device for heating another glass of an electric vehicle. Well, it may be applied to a windshield heating device that heats the windshield of another vehicle, building or building.

[0070]

According to the invention described in claim 1 and the invention described in claim 2, a relatively large reference value is set as a reference value for determining a crack by the energization stopping means for the purpose of preventing erroneous detection. Even in such a case, the detection accuracy of the magnetic balance type current detecting means can be improved, so that when a minute crack is generated in the windshield, the minute crack can be detected. Therefore, even if a minute crack is generated in the windshield, by stopping the energization of the conductive coating by the energization stopping means, it is possible to prevent the local generation of heat or spark in the conductive coating at the minute cracked portion. be able to. Further, since only one magnetic balance type current detecting means is used, the structure of the energization stopping means of the energization control circuit can be simplified, so that the product cost can be reduced.

According to the second aspect of the present invention, even if a relatively large reference value is set as a reference value for judging cracking by the energization stopping means for the purpose of preventing erroneous detection, the magnetic balance type current detecting means is provided. Since the detection accuracy of can be improved, when a minute crack is generated in the windshield, the minute crack can be detected. Therefore, by stopping the power supply to the conductive coating by the power supply stopping means, it is possible to prevent the local generation of heat or sparks in the conductive coating at the minute cracked portion.

[Brief description of drawings]

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

FIG. 2 is an electric circuit diagram showing a second embodiment of the present invention.

FIG. 3 is an electric circuit diagram showing a third embodiment of the present invention.

FIG. 4 is an electric circuit diagram showing a fourth embodiment of the present invention.

FIG. 5 is an electric circuit diagram showing a conventional technique.

[Explanation of symbols]

 1 Windshield Heating Device 2 Windshield 3 First Positive Electrode 4 Second Positive Electrode 5 First Negative Electrode 6 Second Negative Electrode 7 Conductive Coating 8 Power Supply Circuit (Electrification Control Circuit) 14 Crack Detection Device 21 First positive-side conductive wire 22 Second positive-side conductive wire 23 First negative-side conductive wire 24 Second negative-side conductive wire 25 Magnetic balance type current sensor (current detecting means) 26 Control circuit 31 Comparison circuit 32 Arithmetic circuit 41 1st positive side shunt resistance 42 2nd positive side shunt resistance 43 1st negative side shunt resistance 44 2nd negative side shunt resistance

Claims (3)

[Claims] 1. A conductive coating formed on a windshield, a plurality of positive electrodes connected to one end of the conductive coating, and a plurality of positive electrodes arranged to face each of the positive electrodes. A plurality of negative electrodes connected to the other end, a positive-side conductive wire connected to at least one positive electrode of the plurality of positive electrodes, and a plurality of negative electrodes,
A negative side conductive wire connected to at least one negative electrode arranged symmetrically to the at least one positive electrode,
A windshield heating device comprising: an energization control circuit that energizes the conductive coating through the plurality of positive electrodes and the plurality of negative electrodes, wherein the energization control circuit flows through the positive side conductive wire. One magnetic balance type current detecting means for doubling and detecting the difference between the positive side current value and the negative side current value flowing through the negative side conductive wire, and the detection value detected by this current detecting means is equal to or greater than a reference value. A windshield heating device, comprising: an energization stopping means for stopping energization of the conductive film at the time of. 2. A conductive coating formed on a windshield, a plurality of positive electrodes connected to one end of the conductive coating, and a plurality of positive electrodes arranged to face each of these positive electrodes. A plurality of negative electrodes connected to the other end, and at least two first and second positive electrodes of the plurality of positive electrodes
Of the first and second positive side conductive lines connected to each of the positive electrodes and the plurality of negative electrodes, the at least one being disposed symmetrically to each of the first and second positive electrodes. Controlling energization of the conductive coating through the plurality of positive electrodes and the plurality of negative electrodes, which has first and second negative side conductive lines connected to each of the two first and second negative electrodes A windshield heating device comprising: a first positive side current value flowing through the first positive side conductive wire and the first negative side conductive wire. Difference between first negative side current value and difference between second positive side current value flowing through the second positive side conductive wire and second negative side current value flowing through the second negative side conductive wire And one magnetic balance type current detecting means for detecting by adding, and when the detected value detected by this current detecting means is equal to or more than the reference value. , Windshield heating apparatus characterized by comprising a power supply stopping means for stopping the energization of the conductive coating. 3. A conductive film formed on a windshield, a plurality of positive electrodes connected to one end of the conductive film, and a plurality of positive electrodes arranged to face the positive electrode and the other end of the conductive film. A plurality of negative electrodes, and at least two of the plurality of positive electrodes, a first electrode and a second electrode.
First and second positive side conductive wires connected to each of the positive electrodes of
And a first and second negative side conductive line connected to each of at least two first and second negative electrodes of the plurality of negative electrodes, the plurality of positive electrodes and the plurality of negative electrodes. A windshield heating device comprising: an energization control circuit for energizing the conductive coating through an electrode, wherein the energization control circuit is a first positive-side current value flowing through the first positive-side conductive wire. A first positive side shunt resistance for detecting the second positive side shunt resistance, a second positive side shunt resistance for detecting a second positive side current value flowing through the second positive side conductive wire, and a second positive side shunt resistance for flowing the first negative side conductive wire. A current detecting means having a first negative-side shunt resistor for detecting a negative-side current value of 1 and a second negative-side shunt resistor for detecting a second negative-side current value flowing through the second negative-side conductive wire. And a first positive-side current value detected by the first positive-side shunt resistance and the first The difference between the first negative current value detected by the negative shunt resistance and the second positive current value detected by the second positive shunt resistance and the second negative current detected by the second negative shunt resistance. And an energization stopping means for stopping energization to the conductive film when the operation value added by the operation means is greater than or equal to a reference value. Characterizing windshield heating device.