JPH0446847A - Heating device for window glass - Google Patents

Abstract

PURPOSE:To improve detection accuracy, and prevent local heat generation in the window glass heating device in the title and used for defrosting and deicing by forming a power supply circuit via the connection of conductive wires to a plurality of positions for a pair of electrodes so laid as to face window glass. CONSTITUTION:Two conductive sections 3 and 4 are formed at the lamination surface of one of two laminated sheets of plate glass, and the center position of the surface along two sides of respective conductive sections 3 and 4 faced to a wind shield 2 is formed into a pair of electrodes 5 and 6. A conductive film 7 is formed between the aforesaid electrodes 5 and 6. In addition, conductive wires 9 and 10 are led from the electrode 5, while conductive wires 11 and 12 are led from the electrode 6, thereby forming the illustrated power supply circuit 8 together with an automotive battery 13, an automotive generator 14, a relay switch 15 and a relay control circuit 16. According to the aforesaid construction, electric current flows via a plurality of conductive wires, and a current amount through each wire can be made small, thereby enabling the prevention of overheating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a windshield heating device that defrosts and thaws the windshield by heating the windshield.

[Prior Art] For example, Japanese Patent Application Laid-Open No. 61-27741 discloses a resistive film disposed on a window glass, a pair of electrodes connected to two opposing sides of the resistive film, and a pair of electrodes. A power supply circuit that supplies power to the resistive film and stops the supply of power through the resistive film, and defrosts and de-ices the windshield using Joule heat generated by supplying power to the resistive film. A glass heating device is described.

Furthermore, if the electrical resistance value or temperature of the conductive wire connected to one point of each electrode or the resistive coating takes an undesirable value, the power supply circuit determines that a crack has occurred in the windshield and changes the electrical resistance to the resistive coating. and a comparison circuit that stops supplying power to the device.

[Problems to be Solved by the Invention] However, in conventional windshield heating devices, it takes a large amount of power (for example, 1500 W) to raise the temperature of the windshield to a temperature that allows rapid defrosting and thawing of the windshield by applying current to the resistive coating. consume. Further, since the current value that can be passed through the conductive wire connected to one point of each of the pair of electrodes is specified, a large current cannot be passed even if the waste power is large. Therefore, in order to supply the necessary power to this resistive coating, it was necessary to apply a high voltage to the resistive coating using a high voltage power supply. Note that when this windshield heating device is mounted on a vehicle, since the vehicle battery is a 12V power source, a high voltage conversion circuit is required to boost the voltage from 12V to the voltage applied to the resistive coating.

In addition, in conventional window glass heating devices, the conductive wire is connected to one point of the electrode, so that a single current flow is formed through the resistive coating from one electrode to the other electrode. For this reason, when a crack occurs in the windshield, the current concentrates on the resistive coating in the cracked area and sparks fly, causing the resistive coating in this area to generate more heat locally than the resistive coating in other areas. There was an issue of doing so.

Furthermore, the electrical resistance value of the resistive coating varies from product to product due to manufacturing errors in the window glass.

For this reason, in conventional window glass heating devices,
It was necessary to prevent the comparison circuit from determining that an error in the electrical resistance value of the resistive coating due to a manufacturing error is a crack, and thereby stopping power supply to the resistive coating. Therefore, in conventional window glass heating devices, the standard of the comparison circuit is set so that it is not judged that cracks have occurred in the window glass unless the electrical resistance value of the resistive coating changes considerably (for example, about 20% to 50%). Setting the value. However, with this standard value setting method, small changes in electrical resistance due to minute cracks in the windshield (for example, changes of about 5% to 15%) are judged to be normal, resulting in poor detection accuracy. . Furthermore, since the supply of power to the resistive coating is not stopped, there is a problem that localized heat generation at minute cracks cannot be prevented.

SUMMARY OF THE INVENTION An object of the present invention is to provide a window glass heating device that can supply the necessary power to the conductive film at low voltage and prevent local heat generation of the conductive film.

A further object of the present invention is to provide a window glass heating device that can improve detection accuracy and prevent localized heat generation of the conductive coating.

[Means for Solving the Problems] (Claim 1) The window glass heating device of the present invention comprises a pair of electrodes disposed to face the window glass, and a conductive coating formed between the pair of electrodes. and a power supply circuit that supplies power to the conductive film through the pair of electrodes, each of the power supply circuits being connected to a plurality of positions of one of the pair of electrodes. a plurality of first conductive wires;
a plurality of second electrodes each connected to a plurality of positions of the other electrode;
Adopted technical means with conductive wire.

(Claim 2) The windshield heating device of the present invention includes a pair of electrodes disposed opposite to the windshield, a conductive coating formed between the pair of electrodes, and a conductive film formed between the pair of electrodes. and a power supply circuit that supplies power to the conductive coating, the power supply circuit comprising two conductive wires connected to two symmetrical positions of one of the pair of electrodes, respectively; a detection means for detecting a difference between a first current value flowing through one of the two conductive wires and a second current value flowing through the other conductive wire; and the first current value detected by the detection means. and a control means for stopping the supply of power to the conductive film when the difference between the current value and the second current value exceeds a reference value.

[Operation (Claim 1) A plurality of first conductive wires are connected to a plurality of positions of one electrode, and a plurality of second conductive wires are connected to a plurality of positions of the other electrode. Therefore, even if it consumes a lot of power to heat the window glass with the conductive coating, multiple primary
Since the current to be supplied to the conductive film can be passed through the conductive wire and the plurality of second conductive wires separately, the current flowing through each first conductive wire and each second conductive wire is smaller than that in conventional devices.

Note that a plurality of current flows are formed in the conductive film from a plurality of positions on one electrode toward a plurality of positions on the other electrode. Therefore, even if a crack occurs in the window glass, current flows through the conductive coating from a plurality of positions on one electrode to a plurality of positions on the other electrode without passing through the crack.

(M requirement 2) Since the two conductive wires are connected to two symmetrical positions of one electrode, the current values flowing through the two conductive films are approximately equal during normal operation. Further, when a crack occurs in the window glass, the electrical resistance value of the conductive path passing through the cracked portion becomes larger than the electrical resistance value of the conductive path not passing through the cracked portion. Therefore, a difference occurs in the value of the current flowing through the two conductive films.

Then, the first conductive wire flowing through one of the two conductive wires is
The detection means detects the difference between the current value and the second current value flowing through the other conductive wire, and if the difference between the first current value and the second current value is equal to or greater than the reference value, the control means stops the conduction. The power supply to the sexual membrane is stopped.

[Effect of the invention] (Claim 1) Without using an expensive high voltage conversion circuit or high voltage power supply,
It is very economical because it can supply the necessary power to the conductive film at low voltage. Moreover, since two current flows are formed in the conductive film, the current does not concentrate at the cracked portion of the conductive film. Therefore, sparks are not generated at the cracked portions of the conductive coating, so that local heat generation of the conductive coating at the cracked portions can be prevented.

(Claim 2) Since the present invention detects the difference in the value of current flowing through two conductive wires, it is not restricted in any way by changes in the electrical resistance value of the conductive coating due to manufacturing errors in window glass. ,
Therefore, the reference value for determining that cracks have occurred in the window glass can be set to a relatively small value, so even a few small cracks in the window glass can be detected with high accuracy.

Therefore, it is possible to reliably stop the supply of power to the conductive coating even when there is a minute crack in the window glass, thereby preventing local heat generation of the conductive coating at the minute crack.

[Example] A window glass heating device of the present invention will be explained based on an example shown in the drawings.

1 to 3 are claims 1 and 2 of the present invention.
This is an example corresponding to. FIG. 1 is a diagram showing a windshield heating device.

The windshield heating device 1 defrosts and thaws the windshield 2 by heating the windshield 2. The windshield 2 of this embodiment is used for vehicle windshields, and employs laminated glass made by bonding two sheets of glass with an interlayer film such as polyvinyl butyral interposed therebetween.

Two conductive bands 3.4 are formed on one mating surface of the two glass plates by printing or firing a conductive paste such as Ag base. These conductive bands 3.4 are
It is arranged along the side of the windshield 2.

The center portions of these conductive bands 3.4 along two opposing sides of the windshield 2 are made into a first pole 5 and a second electrode 6, which function as a pair of electrodes. This pair of electrodes 5
．． 6, a transparent rectangular conductive film 7 is formed by sputtering or the like.

This conductive film 7 is formed by laminating a highly conductive metal oxide layer and a metal layer. As the metal oxide layer, 20
A ZnO or ZnO2 layer with a thickness of 0A to 600A is preferable, and the metal layer is preferably Ag, Au, or ZnO2 with a thickness of 50λ to 250A.
Aj, Cu layer, etc. are preferable.

This conductive coating 7 is also connected to a power supply circuit 8 via a conductive band 3.4.

The power supply circuit 8 includes two first conductive wires 9 and 10, two second conductive wires 11 and 12, a vehicle battery 13, a vehicle generator 14, a relay switch 15, and a relay control circuit 16.

One first conductive wire 9 includes a portion on one side that is not in contact with the conductive film 7 of the conductive band 3, and connects the left end of the first electrode 5 in the figure and the + side of the vehicle battery 13 to the relay switch 15. Connect via

The other first conductive wire 10 includes the other side portion of the conductive band 3 that is not in contact with the conductive film 7, and connects the right end of the first electrode 5 in the figure and the + side of the vehicle battery 13 to the relay switch 15.
Connect via. A part of the other first conductive wire 10 includes
There is a reverse direction portion 17 in which the direction of current flow is opposite to that of a portion of the first conductive Ii9. Note that the tip of one first conductive wire 9 and the tip of the other first conductive wire 10 are connected at symmetrical positions from the center of the first electrode 5.

One of the second conductive wires 11 includes a portion of the conductive band 4 on one side that is not in contact with the conductive film 7, and connects the left end of the second electrode 6 in the drawing to one side of the vehicle battery 13.

The other second conductive wire 12 includes a portion of the conductive band 4 on the other side that is not in contact with the conductive coating 7 , and connects the right end of the second electrode 6 in the drawing to one side of the vehicle battery 13 . A portion of the other second conductive wire 12 has a reverse direction portion 18 in which the direction of current flow is opposite to that of a portion of the first conductive wire 9 .

Note that the tip of one second conductive wire 11 and the tip of the other second conductive wire 12 are connected at symmetrical positions from the center of the second electrode 6.

The vehicle batch 3 supplies the necessary power to the conductive coating 7 while the engine is stopped and while the engine is rotating.

The vehicle generator 14 is rotationally driven by the engine, supplies power to a vehicle electrical load (not shown) while the engine is rotating, and charges the vehicle battery 13 so that the vehicle battery can be used at any time. It is to be kept in a safe place.

Relay switch 15 is opened and closed by relay control circuit 16, and when closed connects vehicle battery 13 and vehicle generator 14 to the pair of electrodes 5.6, and when opened connects vehicle battery 13 and vehicle generator 14. A pair of electrodes 5.6
Cut off the connection with.

The relay control circuit 16 is a control means of the present invention, and is composed of a microcomputer or a comparator, a relay coil, and the like.

This relay control circuit 16 opens and closes the operation switch 19,
The relay switch 15 is opened and closed according to the outputs of the first differential current detector 20 and the second differential current detector 21. Further, when the operation switch 19 is closed, the relay control circuit 16 closes the relay switch 15 and closes the operation switch 1.
When 9 is opened, relay switch 15 is opened. Further, the relay control circuit 16 is connected to the first differential current detector 20 or the second differential current detector 20 or the second differential current detector 20 or the second
The relay switch 15 is closed when the output of the differential current detector 21 exceeds a reference value.

The operation switch 19 is opened and closed by a vehicle occupant, and sends an open signal to the relay control circuit 16 when opened, and sends a close signal to the relay control circuit 16 when closed.

The first difference current detector 20 is a detection means of the present invention,
The first conductive wire 9 is disposed in the opposite direction portion 17 .
The difference between the current value and the second current value of the other first conductive wire 10 is detected. This first difference current detector 20 detects the current flowing through one first conductive wire 9 and the current flowing through the other first conductive wire 10 when the windshield 2 is normally free of cracks or the like. Since the magnetic flux generated in 20 is canceled, the output of OV is transferred to relay control circuit 16.
send to

In addition, the first differential current detector 20 detects one of the second conductive wires 11 in the event of an abnormality such as a crack occurring in the windshield 2.
A magnetic flux is generated in the first differential current detector 20 by the current flowing through the current and the current flowing through the other second conductive wire 12, and a voltage proportional to the magnetic flux is generated. Therefore, the first difference current detector 2
0 sends to the relay control circuit 16 a voltage value corresponding to the difference between the first current value flowing through one second conductive line 111 and the second current value flowing through the other second conductive line 12.

The second difference current detector 21 is a detection means of the present invention, and comprises:
It is disposed in the reverse direction portion 18, and similarly to the first differential current detector 20, it sends an output of Ov to the relay control circuit 16 when the windshield 2 is normal without cracks or the like. Further, in the event of an abnormality such as a crack in the windshield 2, a voltage value corresponding to the magnitude of the magnetic flux is sent to the relay control circuit 16.

The operation of the windshield heating device 1 of this embodiment will be explained based on FIGS. 1 to 3.

When the operation switch 19 is closed by the vehicle occupant, the relay control circuit 16 closes the relay switch 15, and the power necessary for operating the conductive coating 7 is supplied from the vehicle battery 13. In this way, when electric power is supplied to the conductive film 7, the Joule heat generated in the conductive film 7 defrosts or melts the ice.

Therefore, even if the power consumption is large when using the conductive film 7, the current supplied to the conductive film 7 can be divided into the two first conductive wires and the two second conductive wires. The current flowing through the first conductive line 9.10 and the second conductive line 11.12, respectively, is reduced compared to conventional devices.

Therefore, the first conductive wire 9.10 and the second conductive wire 11.1
When the same current as in the conductive wire of the conventional device is applied to each of the conductive wires 2, the necessary power can be supplied to the conductive film 7 by a lower voltage power source than that of the conventional device. Therefore, the vehicle battery 13
Alternatively, since the power necessary for the conductive film 7 can be supplied only by the generator 14, an expensive high voltage conversion circuit is not required, resulting in a very economical power supply circuit 8.

Note that two first conductive wires 9.10 are connected to two positions of the first electrode 5, and two second conductive lines 11.12 are connected to two positions of the second electrode 6, respectively. , two main current flows are formed in the conductive coating 7 from the first electrode 5 to the second electrode 6. Therefore, even if a crack occurs in the windshield 2, current flows through the conductive coating 7 from the first electrode 5 to the second electrode 6 without passing through the crack, so that the current flows through the conductive coating 7 at the cracked location. Since there is no concentration of current and no sparks,
Local heat generation of the conductive film 7 at the cracked portion can be prevented.

Here, if there are no cracks in the windshield 2, the current values flowing through the two first conductive wires 9.10 and the two second conductive wires 11.12 are equal, so
No magnetic flux is generated and no voltage is generated in the first and second differential current detectors 20.21 disposed in the respective opposite direction portions 17.18. Therefore, the output voltage of the first and second differential current detectors 20.21 is 0■, which is naturally lower than the reference value. Since it is determined that the relay switch 15 is not closed, the closed state of the relay switch 15 is continued.

Furthermore, as shown in FIGS. 2 and 3, when a crack occurs in the windshield 2, the electrical resistance value of the conductive coating 7 is small on the left side (where no crack has occurred) as shown in the figure. It becomes larger on the right side (where the crack is occurring). Therefore, from one first conductive wire 9 to the first
The left side portion of the electrode 5, the left side portion of the conductive coating 7,
The first current value flowing through the left side portion of the second electrode 6 in the drawing, one of the second conductive wires 12, is the same as the current value during normal operation. On the other hand, a second current value flowing from the other first conductive wire 10 to the right side of the first electrode 5, the right side of the conductive film 7, the right side of the second electrode 6, and the other second conductive wire 12. In this case, the electrical resistance value of the conductive film 7 becomes larger than the normal state. That is,
two first conductive lines 9.10 and two second conductive lines 111
There is a difference between the first current value and the second current value of each of 1.12. Thus, the first, disposed in the opposite section 17.18
A magnetic flux is generated in the second differential current detector 20.21, and a voltage proportional to the magnetic flux is generated.

Therefore, the output voltage of the first and second differential current detectors 20.21 has a voltage value corresponding to the size of the crack in the right side portion of the conductive wave II7. If this voltage value is higher than the reference value, the relay control circuit 16 determines that a crack has occurred in the windshield 2, so it opens the relay switch 15 and stops supplying power to the conductive coating 7. Stop.

That is, since the difference between the first current value and the second current value is detected by the first and second difference current detectors 20.21, the conductive coating may Even if the electrical resistance value of the entire windshield 7 varies depending on the product, the occurrence of cracks in the windshield 2 can be detected with high accuracy.

Therefore, the reference value for determining that a crack has occurred in the windshield 2 can be set as low as possible compared to the conventional device. In other words, in the conventional device, the electrical resistance value of the entire conductive coating 7 varies depending on the product due to manufacturing errors of the windshield 2, etc., and therefore the conductive coating 7 is caused by minute cracks that are impossible to detect with the conventional device. Even minute changes in electrical resistance can be detected with high accuracy.

Therefore, it operates reliably even when there is a minute crack in the windshield 2, so that local heat generation of the conductive coating 7 at the minute crack can be prevented.

(Modification) In this embodiment, two difference current detectors 20 are used as detection means.
．． 21 is provided, however, it is sufficient to provide one of the two difference current detectors 20 and 21.

The first current value and the second current value may be different during normal operation, provided that the difference is smaller than the reference value.

In this embodiment, two conductive wires are connected to one electrode, but in claim 1, two or more conductive wires may be connected to one electrode. Further, in claim 2, 2n (n is an integer) conductive wires may be provided on one of the pair of electrodes.

In this embodiment, the supply of power to the conductive film and the stopping of the supply were performed by opening and closing a relay switch, but it may be performed by other switching circuits such as a transistor.

In this embodiment, it has been explained that when a crack in the windshield is detected, the power supply to the windshield is cut off. The shape of .4 may be as shown in FIGS. 4 to 6.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention. Figure 1 is the electrical circuit diagram of the windshield heating device, Figure 2
3 and 3 are plan views of the windshield. 4 to 6 are plan views of windshields according to modified examples of the present invention. In the diagram

Claims (1)

[Scope of Claims] 1) A pair of electrodes disposed opposite to the window glass, a conductive film formed between the pair of electrodes, and an electric power applied to the conductive film through the pair of electrodes. a plurality of first conductive wires each connected to a plurality of positions of one of the pair of electrodes, and a plurality of positions of the other electrode. a plurality of second
A window glass heating device comprising a conductive wire. 2) A pair of electrodes arranged to face the window glass, a conductive film formed between the pair of electrodes, and a power supply circuit that supplies power to the conductive film via the pair of electrodes. The power supply circuit comprises: two conductive wires respectively connected to two symmetrical positions of one of the pair of electrodes, and a conductive wire flowing through one of the two conductive wires. a detection means for detecting a difference between a first current value and a second current value flowing through the other conductive wire; and a difference between the first current value and the second current value detected by the detection means is equal to or greater than a reference value. A window glass heating device comprising: a control means for stopping the supply of electric power to the conductive coating when