JP2519331B2 - Wetness detection sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting the wetness of windshields. More particularly, the present invention relates to a sensor that automatically activates a windshield wiper motor when water is detected on the windshield wetness sensor.

2A. Technical considerations Windshields of vehicles such as automobiles or aircraft are commonly referred to as windshields. The driver observes the outside world through this windshield. Generally, vehicle windshields are laminated structures in which multiple layers of glass and / or plastic are firmly bonded together by an interlayer material. It is important that a clear, undistorted field-of-view area be retained through this windshield, so clean selected areas of the windshield that are contaminated with water and / or dust that can obstruct the driver's vision of the vehicle. To do this, a wiper structure is usually used.

Moisture sensors are used to detect rain on windshields. The sensor is connected to a controller, which automatically activates a windshield wiper motor to remove water and clean the viewing area to be transparent. Usually, the sensor is located on the outer major surface of the windshield,
It has a conductive component with a protective covering. These electrically conductive components are arranged in a fixed relationship to form a variable capacitor which changes the value of the capacitance of the sensor circuit in the presence of moisture on the protective covering.

2B. Related Patents Soundtrack US Patent No. 4,164,868 discloses a capacitive humidity transducer. In this patent, an electrically insulating substrate has at least one pair of conductive coatings,
The pairs of conductive coatings are then spaced from each other along the major surface of the substrate. A dielectric film that is active with respect to water absorption is also disposed on the substrate and is disposed over at least a portion of the coating.
The dielectric constant of this dielectric film changes as a function of the amount of water it absorbs. The dielectric film has a conductive layer through which water can penetrate. The dielectric film holds the outer layer in permanent contact with at least one of the coatings, whereby
It makes it possible to measure the capacitance between these coatings. The value of this capacitance will indicate the humidity of the atmosphere.

Freud, U.S. Pat. No. 4,429,343, discloses a humidity sensing element having a pair of thin film platinum fingers deposited in a finger interdigitated form on the surface of a glass substrate. The membrane is coated with a coating of a water absorbing material such as cellulose acetate butyrate or silicone rubber. The sensitivity of this sensor to humidity results from the humidity-related change in dielectric constant that occurs in the coating on the finger. As this dielectric constant changes, the capacitance between the interdigitated fingers changes.

Iyoda U.S. Pat. No. 4,639,831 discloses a transparent sensor for detecting rain on a window glass. The rain sensor is made of a transparent material and is located in the wiper-cleaned area of the outside surface of the glazing. The sensor has a pair of electrodes with interdigitated finger components. These finger parts are electrically isolated from each other due to the gaps between them. A transparent insulator protective film covers the electrode and the gap. These interdigitated components form a capacitor having a variable capacitance value. When a drop of water is on a portion of the protective covering between a pair of finger parts, that is, on a portion of the protective covering that is aligned with the gap, the dielectric constant of the water droplet is air. Since it is larger than the dielectric constant of, the capacitance value of this capacitor is larger than the normal capacitance value. Therefore, when a large number of water drops are present on the protective coating, the overall capacitance value obtained between the electrodes is large.

SUMMARY OF THE INVENTION One object of the present invention is to have a sensor that detects moisture on the surface of a substrate. In one particular embodiment of the invention, the substrate is a multilayer windshield having an inner glass layer, an outer glass layer and an intermediate layer separating these glass layers. A first transparent conductive coating and a second transparent conductive coating are securely attached to the outer surface of the outer glass layer of the windshield. Here, the first cover is arranged with a space from the second cover. Third transparent conductive coating and fourth
Transparent conductive coatings are spaced and firmly attached to the flexible polyester membrane. This membrane is located between the intermediate layer and the inner glass layer. The first cover is then arranged so as to be on at least a part of the third cover and the second cover is arranged so as to be on at least a part of the fourth cover. The third cover is connected to the electrical signal generator and the fourth cover is connected to the electrical signal receiver. Here, the first coating body and the third coating body and the second coating body and the fourth coating body form a coupled capacitive circuit. Each of the first and third coatings and the second and fourth coatings constitutes a capacitor in which the outer glass layer and the intermediate layer act as a dielectric between these coatings.

During operation, sufficient moisture accumulates on the windshield sensor to be pumped into the third cover when bridging the gap between the first and second conductive covers. , And through the coupled capacitive circuit, the nature of the electrical signal will change. This changed signal is detected by a signal receiver connected to the fourth cover. In response to the received signal, the windshield wiper electric motor is activated and the outer surface of the windshield is cleaned.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a capacitively coupled rain sensor incorporating the features of the present invention.

2 is a cross-sectional view of the capacitor plate of the present invention taken along line 2-2 of FIG.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 1 showing the conductors from the capacitor plates and the inner plates located inside.

FIG. 4 is a schematic diagram of one type of circuit that can be used with the coupled capacitor rain sensor shown in FIG.

DETAILED DESCRIPTION OF THE INVENTION Although the present invention is described in the context of laminated windshield structures, the present invention may be used in any application where it is necessary to detect surface moisture. it can.

1 through 3, the rain sensor 10 that is the subject of the present invention is incorporated into a conventional three-layer windshield 12. This three-layer windshield 12 is an outer glass layer
14, an inner glass layer 16, and an intermediate flexible layer 18. The sensor 10 can be placed anywhere on the windshield 12, but when cleaning the field of view of the windshield, it may be placed on the area to be cleaned by a windshield wiper (not shown). preferable.

In the particular embodiment of the invention shown in FIGS. 1-3, the outer surface 20 of the outer layer 14 is coated with two conductor film coatings 22 and 24. Two of these conductor film coatings 22 and 24 are separated from each other by a predetermined gap 26 and are electrically insulated from each other. Normal,
The gap 26 should not be larger than the size of the small raindrops or fog that impacts or accumulates on the windshield 12.
The preferred size of the gap 26 is on the order of about 0.020 inches (0.5 millimeters). The difference from other rain sensors is that there is no protective layer over the covers 22 and 24, so the rain sensor of the present invention is exposed. Therefore, these coatings must withstand abuse.
That is, it must have abrasion resistance, solvent resistance, and weather resistance. The coatings 22 and 24 are formed on the outer surface 20 of the outer layer 14 by any of the well known coating methods that do not significantly impair the transparency of the windshield, such as vacuum deposition or pyrolysis deposition. Deposited on top. Cover 22
And 24 are interdigitated. That is, the protrusions 28 of the cover 22 are located between and away from the complementary protrusions 30 of the cover 24. The gap 26 electrically insulates the protrusion 28 and the protrusion 30 from each other.

A second set of conductive coatings is provided in the windshield 12. The position where this second set of conductive coatings can be provided is
It is preferably located along the surface 32 of the inner layer 16.
In the particular embodiment shown in FIGS. 1-3, the coverings 34 and 36 include flexible carriers, such as plastic membranes, inserted between the inner layer 16 and the intermediate layer 18. 38
Attached to. In the preferred embodiment, coatings 34 and 36 are adjacent to intermediate layer 18. The surface 39 of the carrier 38 is provided with an adhesive coating 41, the carrier 38 and the glass layer.
Between 16 and 16, the windshield is prevented from delamination. The coating can be, for example, a pressure sensitive acrylic adhesive or a primer with polyvinyl butyral (21/2% by weight) dissolved in methanol. The covers 34 and 36 need not necessarily be interdigitated, but are arranged to underlie the covers 22 and 24, respectively. However, coatings 34 and 36 are separated from coatings 22 and 24, respectively, by outer layer 14 and intermediate layer 18. Like the covers 22 and 24,
The coatings 34 and 36 are electrically isolated from each other, but unlike the coatings 22 and 24, these coatings are sealed in the windshield 12 and thus are not essential. It does not have to withstand abuse. The coatings 34 and 36 can be made by conventional methods that do not significantly impair the optical properties of the windshield 12 or carrier 38. An embodiment in which the coatings 34 and 36 are attached to the carrier 38, as shown in the drawings of FIGS. 1-3, rather than being attached directly to the surface 32 of the inner layer 16. So the pyrolysis deposition method probably cannot be used. This is because it distorts the carrier 38 and causes optical defects in the windshield 12. Therefore, vacuum evaporation or magnetic field sputtering deposition may be the preferred method.

Conductor portions 40 and 42 are respectively covered by sheaths 34 and 36.
To the end 44 of the windshield 12 and are electrically connected to an electrical signal generator 46 and an electrical signal receiver 48, respectively. Both the electrical signal generator 46 and the electrical signal receiver 48 can be incorporated into the controller 50 (shown in FIG. 4), as discussed below. In the particular embodiment shown in FIG. 1, a portion of the inner layer 16 is provided at the end 44.
Can be removed along with the carrier 38
As the wires are pulled away from the mid layer 18, the ends 40 and 42 of the wire are
The ends of the can be exposed and an electrical connection can be made.

In one particular embodiment of the rain sensor, the glass layers 14 and 16 are 0.090 inch (2.3 mm) thick Solex glass and the intermediate layer 18 is 0.030 inch (0.8 mm) thick polyvinyl butyral. Is. The coatings 22 and 24 are transparent tin oxide having a surface resistivity in the range of about 50 to 1000 ohms / square. Flexible carrier 38 is a polyester film having a thickness of about 0.0035 inches (0.09 millimeters). The coatings 34 and 36 are transparent metal films having silver metal, zinc tin metal, and zinc tin oxide, and have a resistance value of about 15 ohms / square or less.

FIG. 4 is a schematic diagram of the circuit 54 showing the operation of the sensor 10. The covers 22 and 34 are plate components with a dielectric, ie the glass layer 14 and the intermediate layer 18, disposed between them, which form the capacitor 56. Similarly, the covering
24 and 36 act as plate components with dielectrics 14 and 18 disposed therebetween, which form capacitor 58. The interdigitated ridges 28 and 30 form an impedance network 60. Each adjacent pair of protrusions acts essentially as a parallel connected capacitor 62 and resistor 64, as discussed below.

A series of signals from the signal generator 46 is circuited through conductor 40.
Input into 54 and the output signal is sent through conductor 42 to a signal receiver 48. Changes in the output signal are monitored by controller 50. When the sensor 10 is dry, the capacitance value of the capacitor 62 is high and the resistor
The resistance value of 64 is high. Therefore, the impedance network 60 functions substantially like a capacitor, ie, the signal passes primarily through the capacitor 62 and through the circuit 54, producing an output signal characteristic of the dry state. However, when there is water on the sensor 10, the capacitance value of the capacitor 62 decreases and the resistance value of the resistor 64 drops. Therefore, the impedance network 60 functions essentially like a resistor, that is,
The signal passes primarily through resistor 64 and through circuit 54, producing a different signal characteristic of the wet condition. This signal can be distinguished from the dryness signal.

In one particular embodiment, but not limited to the present invention, the input signal that can be monitored is a series of square voltage pulses. For this input signal, the dry state output signal is a series of spiked pulses and the wet state output signal is a series of attenuated square wave signals. Other signals characteristic of the circuit, such as current or resistance, can also be used to detect changes from dry to wet or from wet to dry. Controller 50 operates windshield wiper motor 66 in response to the wet state output signal to activate a wiper (not shown), thereby cleaning the field of view of windshield 12.

When activated, the wiper motor 6 can operate in one of several modes. If desired, a windshield wiper (not shown) can clean the windshield only once, or it can operate only during a predetermined time interval, Alternatively, it is possible to perform cleaning by reciprocating a preset number of times. Further, the electronic circuitry of the windshield wiper control device (not shown) provides for the motor 66 to operate if the motor 66 is repeatedly operated to reciprocate a predetermined number of times during a set time interval. Can remain active until the vehicle driver manually switches it off.

When more water is present above the gap 26 of the sensor 10,
Larger currents flow from jacket 22 to jacket 24, thus changing the selected monitorable signal of circuit 54.
If necessary, the signal receiver 48 or controller 50
One or more sensing circuits 68 may be included to monitor these signals. By connecting the controller of the variable speed wiper motor 66 to the sensing circuit 68, the controller 50 can change the wiper speed in response to the output signal received by the sensing circuit 68, thus automatically adjusting the wiper speed. Can be controlled.

It should be noted that the arrangement of the conductors in this preferred embodiment of the present invention avoids the drawback of the windshield wiper electric motor continuing to operate and fail. In particular, the conductors 40 and 42 are arranged in the windshield 12 between the glass layer 14 and the glass layer 16, so that these conductors remain electrically insulated from each other, and , 40 due to moisture, deposits or salt deposits (which may render the surface conductive), or due to the vehicle body (not shown) around the windshield 12 It is not electrically interconnected and therefore the capacitor is not bypassed.

It will be further appreciated by those skilled in the art that multiple sensors may be located at different locations on the windshield to independently control the different windshield motors. For example, arranging the first sensor in the visual field of the vehicle driver,
The second sensor can then be located in the passenger's field of view.

Further, the sensor 10 can be used in a windshield having a multi-layer structure (not shown), i.e., a windshield having one outer glass layer and an inner shock-absorbing laceration prevention layer. As in the embodiment shown in FIGS. 1-3, the coating of sensor 10 would be located along the inner and outer surfaces of the glass layer.

Moreover, the sensor 10 is not limited to being used only on the outer surface of the windshield. For example, the sensor 10 places the coatings 22 and 24 on the inner surface of the glass layer and, as described above, covers 34 on the opposite major surfaces of the glass layer.
The placement of and 36 can be used to detect fog or frost on the inside surface of the vehicle window. The sensor 10 will actuate a window cleaning device, such as a window anti-fog device or an electrically heatable window glass. If the coverings 34 and 36 are disposed on surfaces exposed to the ambient environment, the coverings are either abuse resistant jackets or are additionally protected by abuse resistant jackets. There must be.

Obviously, according to the invention, the coverings 34 and 36 are not limited to being arranged between the intermediate layer 18 and the glass layer 16. For example, the carrier 38 can be placed in position within the windshield 12, and the coverings 34 and 36 can be placed on the side facing the adjacent glass layer 14 or 16 or on the opposite side. . Further, the coatings 34 and 36 can be attached directly to the surface 70 of the glass layer 14 so that the glass layer 14 acts as the dielectric layer of the capacitor, or the coatings 34 and 36 are
Attached to the surface 72 of 16 the entire windshield 12 can also act as a dielectric layer.

In contrast to other rain sensors which constantly monitor capacitance changes caused by moisture absorbing dielectric coatings, the present invention has a protective coating over the exposed sensor coating. The sensor 10 of the present invention requires only observable changes in the nature of the electrical communication between the cladding 20 and the cladding 24. Therefore, it is important that at least a portion of the coatings 22 and 24 remain exposed and that moisture bridges the gap 26, causing a change in the circuit 54.

The embodiments of the invention described above are for illustration only. It will be appreciated that various modifications are possible within the scope of the invention as defined in the following claims.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliographic references Sho 59-34354 (JP, U)

Claims (19)

(57) [Claims] 1. A dielectric substrate comprising a glass layer through which the outside world can be seen, fixed and spaced from each other and on a first major surface of said substrate. A first electrically conductive component and a second electrically conductive component that are directly disposed, a third electrically conductive component that is fixed and spaced from each other, and is disposed on a second major surface opposite the substrate, and A fourth conductive component, wherein the first conductive component is on at least a portion of the third conductive component and the second conductive component is on at least a portion of the fourth conductive component. And a device for electrically connecting only the third conductive component and the fourth conductive component, and the first and second conductive components and the third and fourth conductive components. The glass layer dielectric substrate sandwiched between parts is A wetness detection sensor, which is the glass layer of the vehicle window. 2. The device according to claim 1, wherein the device for making the electrical connection electrically connects an electrical signal generator to the third conductive component, and the device for electrical signal reception is the fourth.
And a device for electrically connecting to a conductive part. 3. The wetness detection sensor of claim 2, further comprising a device responsive to the signal receiver for activating a device for cleaning the first major surface of the substrate. 4. The conductive coating according to claim 3, wherein the first conductive component and the second conductive component and the third conductive component and the fourth conductive component are fixed to the main surfaces of the substrate facing each other. Wetness sensor that is the body. 5. The wetness detection sensor according to claim 1, wherein the substrate and the conductive component are transparent. 6. The wetness detection sensor according to claim 5, wherein the conductive component is a metal coating. 7. A first dielectric substrate which is made of a glass layer and which allows the outside world to be seen through the glass layer. The first dielectric substrate is fixed and spaced from each other, and the first dielectric substrate A first electrically conductive component and a second electrically conductive component directly disposed on one major surface, fixed to each other and spaced apart, and adjacent to a second major surface opposite the first substrate. Electrically conductive third component and fourth electrically conductive component, the first electrically conductive component being on at least a portion of the third electrically conductive component and the second electrically conductive component being at least a portion of the fourth electrically conductive component. The third conductive component and the fourth conductive component
An electrically conductive component and at least one additional substrate immovably secured to the second major surface of the first substrate to create a composite assembly, the first and second electrically conductive components A wetness detection sensor, wherein the first dielectric substrate of the glass layer sandwiched between the third and fourth conductive components is a glass layer of a vehicle window. 8. The wetness detection sensor according to claim 7, wherein the first conductive component and the second conductive component are fixed to the first main surface of the first substrate. 9. The wetness detection sensor according to claim 8, wherein the third conductive component and the fourth conductive component are fixed to a main surface of one of the at least one additional substrate. 10. The wetness detection sensor according to claim 9, further comprising a device for electrically connecting only the third conductive component and the fourth conductive component. 11. The wetness detection sensor according to claim 8, wherein the third conductive component and the fourth conductive component are fixed to a flexible carrier arranged on the second main surface of the first substrate. 12. The wetness detection sensor according to claim 11, further comprising a device for electrically connecting only the third conductive component and the fourth conductive component. 13. A first dielectric substrate comprising a glass layer having a first major surface and a second major surface, through which the glass can be seen to see the outside world, and a first major surface and a second major surface. A wetness detection sensor comprising: an intermediate layer having: a second dielectric substrate that is formed of a glass layer having a first major surface and a second major surface and can see the outside world through the first dielectric. A second major surface of the substrate adheres to the first major surface of the intermediate layer, a first major surface of the second dielectric substrate adheres to the second major surface of the intermediate layer, the wetness detection sensor further comprising: A first conductive component and a second conductive component that are fixedly arranged with a space between and fixed to the first main surface of the first dielectric substrate; the first dielectric substrate and the second conductive component; A fixed third fixedly arranged and spaced from each other between the dielectric substrates. A conductive component and a fourth conductive component, wherein the first conductive component overlaps at least a part of the third conductive component, the second conductive component overlaps at least a part of the fourth conductive component, and The wetness detection sensor, wherein the dielectric substrate and the second dielectric substrate are glass layers of a vehicle window. 14. The wetness detection sensor according to claim 13, wherein the third conductive component and the fourth conductive component are arranged on one of the main surfaces of the intermediate layer. 15. The wetness detection sensor according to claim 14, wherein the third conductive component and the fourth conductive component are arranged between the intermediate layer and the second dielectric substrate. 16. The wetness detection sensor according to claim 13, further comprising a device for electrically connecting only the third conductive component and the fourth conductive component. 17. A first dielectric substrate having a first major surface and a second major surface, an intermediate layer having a first major surface and a second major surface, and a first major surface and a second major surface. In a wetness detection sensor including a second dielectric substrate, the second main surface of the first dielectric substrate is fixed to the first main surface of the intermediate layer, and the first main surface of the second dielectric substrate is the intermediate surface. A first conductive component secured to the second major surface of the layer, the wetness detection sensor further fixedly spaced from each other and secured to the first major surface of the first dielectric substrate; A second conductive component, and a fixed third conductive component and a fourth conductive component that are fixedly arranged at a distance from each other between the first dielectric substrate and the second dielectric substrate. And wherein the first conductive component overlaps at least a portion of the third conductive component, and the second conductive component An article overlaps at least a portion of the fourth conductive component, the wetness detection sensor further comprising a device for making electrical connection to only the third conductive component and the fourth conductive component, the third conductive component The wetness detection sensor, wherein the component and the fourth conductive component are fixed to a flexible carrier disposed between the intermediate layer and the second substrate. 18. An apparatus for electrically connecting an electrical signal generator to the third conductive component, and an apparatus for electrically connecting an electrical signal receiver to the fourth conductive component according to claim 17. A wetness detection sensor further comprising: 19. The wetness detection sensor of claim 18, further comprising a device responsive to the signal receiver for activating a device for cleaning the first major surface of the first substrate.