WO2007140658A1

WO2007140658A1 - A plane capacitive sensor and a method for detecting environmental variation of vehicle windscreen

Info

Publication number: WO2007140658A1
Application number: PCT/CN2006/001973
Authority: WO
Inventors: Tengchen Sun
Original assignee: Tengchen Sun
Priority date: 2006-06-08
Filing date: 2006-08-04
Publication date: 2007-12-13
Also published as: CN101087135A; CN100571035C

Abstract

A plane capacitive sensor includes a plane capacitor (1), a plane capacitor compensator (2) for eliminating disturbing signals, and a sensor detection circuit. The sensor adopts two plane capacitors, and one capacitor serves as a detecting capacitor, and another serves as a compensating capacitor. The fixing position and the shape of the compensating capacitor are changeable so as to make the capacitor become insensitive to the rain on the outside surface of windscreen, but sensitive to temperature shift and electromagnetic disturbance. When suffered temperature shift or electromagnetic disturbance, the measurements of the detecting capacitor and the compensating capacitor are varied simultaneously and their variation magnitudes are equal with each other approximatively. When suffered variation of the rain, the measurement of the detecting capacitor is varied and the measurement of the compensating capacitor keeps constant substantially.

Description

Planar capacitive sensor

And method for detecting environmental changes of automobile windshield

The present invention relates to a device for detecting environmental changes in an automobile windshield, and more particularly to a detecting device for detecting a change in rainfall of a windshield of a vehicle and a detecting method using the same.

Background technique:

Since the beginning of the 21st century, automotive electronics and intelligence have become the direction and frontier of the development of automotive industry technology. The safety and humanization of automobiles have also become the focus of major automobile manufacturers. The automatic detection system is not only focused on the humanized care that is convenient for driving, but more importantly, the automatic detection system is an important part of the active safety system of the vehicle. In rainy weather or in a relatively high air relative humidity environment, the driver's line of sight is often affected by excessive rain on the surface of the windshield.

The key technology of the automatic wiper system in the prior art is the raindrop sensor technology. Objectively speaking, the world's raindrop sensor technology is still not mature enough, even though some famous automobile manufacturers such as German Volkswagen, Chrysler, France, France. Citroen and others have successfully equipped their car products with an automatic wiper system. However, due to the immature raindrop sensor technology, it is difficult to install, costly, and has a high misoperation rate.

In order to solve the above problems, the applicant applied for ZL03160008. No. 5 invention patent on September 19, 2003, which is a flat capacitive intelligent automatic wiper system sensor, including: one installed in the front windshield of the car a planar capacitor on the surface of the glass to act as a sensor for the sensor, wherein the two plates of the planar capacitor are placed on the same plane; a sensor detection circuit detects the change in capacitance of the planar capacitor due to environmental influences And generating a control signal for controlling the operation of the wiper according to the detected change in capacitance. This solution can solve the problems of many prior art mentioned above by installing the sensor on the inner surface of the front windshield of the automobile and within the range of the wiper brushing. However, this solution does not solve the problem that temperature drift and electromagnetic interference affect the detection accuracy of the sensor. First, the two electrodes of the planar capacitor are directly attached to the inner surface of the front windshield of the car, due to the speed of the car. The temperature of the front windshield changes greatly, and the temperature directly affects the change of the dielectric constant of the glass, causing the temperature drift of the measurement signal. The consequence is that the measurement sensitivity is unstable, and even the wiper malfunctions. Secondly, it is attached to the front windshield of the automobile. The planar capacitor on the inner surface forms a receiving antenna for the wireless electromagnetic signal and cannot be shielded. When strong wireless electromagnetic interference is encountered, the wiper may malfunction.

Another example is the German patent DE102004026716. 2, which is applied by Siemens, with a magnetic field capacitor surrounded by a first carrier layer. There is also a second carrier layer in this sensitive element parallel to the surface of the first carrier layer. The carrier layer surrounds another magnetic field capacitor. An intermediate layer which is electrically conductive is mounted between the first carrier layer and the second carrier layer. If this sensitive element is used in a structure corresponding to the invention, condensation can be detected in both the inner and outer chambers. In the second carrier layer space in which the second field capacitor is located, it is necessary to plate the inner wall of the dielectric wall in which the inner and outer chambers are separated from each other. The above scheme can simultaneously detect rain and fog inside the vehicle, but it also has the problem of not eliminating temperature drift and electromagnetic interference.

Summary of the invention:

One of the technical problems to be solved by the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a planar capacitive sensor capable of eliminating temperature drift and electromagnetic interference. The device has a simple structure and can overcome existing photoelectric and planar capacitances at the same time. The type of detection device has the advantages of small measurement area, inability to measure rainwater thickness, vulnerability to pollutants, excessive installation requirements, poor adaptability, and high cost.

Another technical problem to be solved by the present invention is to provide a method for detecting environmental changes of an automobile windshield capable of eliminating temperature drift and electromagnetic interference, and the method is simple and practical, and is advantageous for promotion.

According to a technical problem to be solved by the present invention, a planar capacitive sensor includes a planar capacitor mounted on a front windshield of a vehicle and a sensor detecting circuit connected to the planar capacitor, the planar capacitor serving as a sensor of the sensor, wherein the two plates of the planar capacitor are placed on the same plane, the sensor detecting circuit detects a change in capacitance caused by the environmental impact of the planar capacitor, and changes according to the detected capacitance Generating a control signal for controlling the operation of the wiper device, the sensor detection circuit is further connected Connected to a planar capacitance compensator for canceling the interference signal, the two plates are placed on the same plane, the planar capacitance compensator is only used as a sensitive component for detecting an interference signal, and the sensor detection circuit detects the planar capacitance compensator The change in capacitance caused by the influence of the interference signal, and the change in capacitance caused by the environmental impact of the planar capacitor is compensated according to the detected change in capacitance.

A planar capacitive sensor according to the present invention further has the following subsidiary technical features - an embodiment of the present invention provides that the planar capacitive compensator and the planar capacitor are disposed in parallel with each other on the windshield of the automobile.

The planar capacitor is located within the interlayer of the automotive windshield, and the planar capacitive compensator is located on the inner surface of the automotive windshield opposite the planar capacitor.

The planar capacitor is in close contact with the inner surface of the windshield of the automobile, and the planar capacitor compensator is located behind the planar capacitor and forms a certain distance from the planar capacitor through a layer of insulating material.

According to another embodiment of the present invention, the planar capacitor compensator is mounted on the same plane as the planar capacitor.

The planar capacitor compensator and the planar capacitor are mounted on an inner surface of an automobile windshield.

The planar capacitance compensator is located within the planar capacitor.

The planar capacitance compensator abuts a side of the planar capacitor.

The capacitor compensator shares one of the plates with the planar capacitor.

The total area of the two plates of the planar capacitor compensator is smaller than the total area of the two plates of the planar capacitor, and the spacing between the two plates of the planar capacitor compensator is smaller than the thickness of the glass at the position where the planar capacitor The spacing between the two plates is equal to or greater than the thickness of the glass at the location.

The conductive material of the planar capacitor and the planar capacitor compensator is copper, aluminum, silver, conductive rubber, conductive plastic, transparent conductive film or conductive adhesive; bonding, pressing or spraying on the windshield of the automobile On the inner surface of the glass. The planar plates of the planar capacitor and the planar capacitor compensator are rectangular, ring-shaped, fan-shaped, triangular or polygonal.

The total area of the two plates of the planar capacitor is 10-20 square centimeters, and the total area of the two plates of the planar capacitance compensator is 5-11 square centimeters.

An embodiment of the sensor detection circuit provided by the present invention is that the sensor detection circuit includes a signal generator, a program-controlled analog signal amplification and filtering circuit, a differential circuit, an analog-to-digital conversion circuit, and a microprocessor, and the signal generator Generating a test signal of the access plane capacitor and the planar capacitor compensator, and when the test signal flows through the planar capacitor and the planar capacitor compensator, it is changed by the external environment, and the two changed test signals are input respectively. a program-controlled analog signal amplification and filtering circuit, after performing amplification and filtering, generating two DC voltage signals, and the two DC voltage signals are differentially processed by the difference circuit to generate a differential signal, wherein the differential signal passes through the module The number conversion circuit converts to a digital signal, the microprocessor receives the digital signal, and processes the digital signal to form a sensor digital output signal that controls operation of the device.

According to still another embodiment of the sensor detection circuit provided by the present invention, the sensor detection circuit includes a signal generator, a program-controlled analog signal amplification and filtering circuit, an analog-to-digital conversion circuit, and a microprocessor, and the signal generator generates a connection. The test signals of the planar capacitor and the planar capacitor compensator are changed by the external environment when the test signal flows through the planar capacitor and the planar capacitor compensator, and the two changed test signals are respectively input into the program-controlled simulation. a signal amplifying and filtering circuit, after performing amplification and filtering, generating two DC voltage signals, wherein the DC voltage signals are respectively converted into two digital signals via the analog to digital conversion circuit, and the microprocessor receives two of the digital signals, A differential operation is performed on the two digital signals, and a digital output signal of the sensor that controls the operation of the device is formed according to the result of the differential operation.

The planar capacitor is installed in the working area of the automobile wiper. While the device is working, the device continues to detect the glass surface and form a feedback signal to further control the operation of the device to form a closed loop control system.

The test signal is a sine wave signal, a square wave signal or a triangular wave signal.

The frequency of the test signal is 100 kHZ - 1000OHHZ, the planar capacitor and the flat The surface capacitance compensator has a static capacitance value between 50 and 400 pf.

According to a second aspect of the present invention, a method for detecting a change in an environment of an automobile windshield is provided as follows:

a, initialize the sensor;

b. The signal generator in the sensor generates a test signal, and the test signal is respectively transmitted to the planar capacitor and the planar capacitor compensator;

c. respectively detecting changes caused by the influence of the external environment when the test signal passes through the planar capacitor and changes caused by the interference signal when the test signal is passed through the planar capacitor compensator; d. testing the two changes detected The signal is subjected to a differential operation;

e. The processing unit generates a control signal according to the differential signal;

f, transmitting control signals to the device;

g. The sensor detects the glass surface again, generates a feedback signal, and transmits it to the processing unit to form a closed-loop control system.

The planar capacitive sensor provided in accordance with the present invention has the following advantages over the prior art: The present invention employs a biplanar capacitor in which one planar capacitor acts as a measurement capacitor and the other acts as a compensation capacitor by changing the mounting position and shape of the compensation capacitor. It is not sensitive to rain on the outer surface of the glass, but sensitive to temperature drift and electromagnetic interference. When there is temperature drift or electromagnetic interference, the measured values of the measuring capacitance and the compensation capacitance occur simultaneously and the amplitude of the change is approximately equal. When the rain changes, the measured capacitance value changes, and the compensation capacitance value remains basically unchanged. The above characteristics can be used to differentially compensate the sensor measurement value, effectively reducing the adverse effects of temperature drift and electromagnetic interference on the sensor measurement sensitivity, and avoiding the wiper malfunction.

At the same time, the present invention has the following advantages as a built-in planar capacitive sensor:

1. The measuring area is large. The planar capacitor plate can be made into any shape, and the measurement area can be arbitrarily expanded without affecting the driver's line of sight. This can fundamentally avoid the drawback that the detection system of the photoelectric raindrop sensor is too small to reflect the sluggishness.

2. It can measure the thickness of rainwater attached to the glass surface. Since the dielectric space of the planar capacitor is a space near the surface of the glass and glass above the plate and the outer surface is approximately a semi-ellipsoidal shape, the variation of the thickness of the rainwater will cause the dielectric constant of the dielectric of the capacitor. The change causes a change in capacitance. This overcomes the defect that the photoelectric raindrop sensor cannot measure the thickness of the rainwater caused by the slow movement of the automatic wiper system and thus affects the rain effect.

3. Not susceptible to interference from pollutants. Since the relative dielectric constant of water is much larger than the general pollutants, the planar capacitive sensor can easily distinguish the pollutants from the changes in the water to the capacitance, thus solving the photoelectric raindrop sensor due to the influence of pollutants. The problem of malfunction of the automatic wiper system.

4. The installation process is very simple. Planar capacitive sensors can be formed by bonding, crimping, spraying, or various metallization methods on the glass surface to form planar capacitors on the inner surface of the glass, without the need for precise positioning like a photoelectric raindrop sensor.

5. Adaptability. Since the dielectric constant of water is several times larger than that of glass, the influence of changes in glass material and thickness on the accuracy and sensitivity of the sensor is negligible. The same planar capacitive sensor can be adapted to almost all kinds of automotive glass. There is no need to design special sensors for various automotive glass.

6. Material, installation, and labor costs are significantly reduced. Planar capacitive sensors can be selected from a variety of conductive materials, such as: copper foil, aluminum foil, conductive rubber, conductive plastic film, glass surface spray metallization, etc., and the amount is very small, generally only about 10 square centimeters, so the material cost is extremely low. Due to the simple installation, the installation and installation man-hour costs are much lower than the photoelectric rain sensor.

7. The invention can be conveniently installed in the range of brushing of the automobile wiper. Therefore, the effect of the team wiper work can be detected to form a closed loop control system.

A method for detecting environmental changes of a windshield of an automobile according to the present invention has the following advantages: The method simultaneously detects a measurement signal and a compensation signal, and differentially processes the two signals, and controls the operation of the related device according to the differential signal. The effect of temperature drift and electromagnetic interference on the sensor is eliminated, and the method is advantageous for implementation, and is suitable for promotion and application.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 is a point charge electric field line distribution diagram;

Figure 2 is a parallel plate type capacitor electric field line distribution diagram;

3 is a field line distribution diagram of a planar capacitor of two rectangular plates of the present invention;

4 is a schematic view showing a measurement space formed by a planar capacitor of two rectangular plates of the present invention; Figure 5 is a diagram showing an equivalent capacitance measurement model of the present invention;

Figure 6 is a cross-sectional view showing an embodiment of the present invention, showing a plane capacitor and a planar capacitor compensator disposed on the interlayer and the inner surface of the windshield of the automobile, and simultaneously showing the measurement formed by the two. space.

Figure 7 is a cross-sectional view showing another embodiment of the present invention, showing a planar capacitor and a planar capacitor compensator disposed on the inner surface of the windshield of the automobile, and showing the measurement space formed by the two. .

Figure 8 is a schematic view showing a rectangular plate of a planar capacitor and a planar capacitor compensator in the present invention.

Fig. 9 is a schematic view showing a state in which the plates of the planar capacitor and the planar capacitor compensator are annular in the present invention.

Figure 10 is a schematic illustration of the planar capacitor and planar capacitance compensator disposed on the same plane in accordance with the present invention.

Figure 11 is a schematic view showing that the plates of the planar capacitor and the planar capacitor compensator of the present invention are rectangular and share one of the plates.

Fig. 12 is a view showing the plate of the planar capacitor and the planar capacitor compensator of the present invention in a ring shape and sharing one of the plates.

Figure 13 is a cross-sectional view showing the mounting structure of the present invention.

Figure 14 is a block diagram of an embodiment of a planar capacitance detecting circuit of the present invention.

Figure 15 is a block diagram showing another embodiment of the planar capacitance detecting circuit of the present invention.

The embodiments are described below in conjunction with the accompanying drawings, and the invention will be described in detail -

Before describing the present invention in detail, the prior art and the working principle of the present invention will be briefly described. The conventional capacitive sensor is based on a parallel plate type capacitor, and its principle is: If the edge effect of the non-uniform electric field is not considered, the two parallel plates a capacitor composed of

Oe*S/d

Where e is the dielectric constant of the dielectric between the plates, € e0« er, e0 is the dielectric constant in vacuum, e0=8. 854* 10— ^{1 2} F/m, er is the dielectric relative to the dielectric of the vacuum Constant, air phase For the dielectric constant er l, other media er>l; S is the area of the plate; d is the pitch of the plates. Due to the change of the measured medium, the change of the parameter e:, S, d of the capacitive sensor causes the capacitance C to change accordingly. Accordingly, the conventional capacitive sensor can be divided into three types according to the change of different parameters: variable pitch type (parameter d change); variable area type (parameter S change); variable dielectric constant type (parameter e change).

The planar capacitor proposed by the present invention theoretically breaks the mindset of the conventional capacitive sensor based on the parallel plate type capacitance principle, and places the two plates of the capacitor on the same plane with a certain gap instead of being placed in parallel. It does not belong to any of the three types of conventional capacitive sensors described above. It is a comprehensive capacitive sensor that combines the characteristics of variable pitch, variable area and variable dielectric constant capacitance sensors.

The principle of capacitance measurement of the present invention is as follows:

According to the principle of field strength vector superposition of electric field theory, we know that the characteristics of capacitors can be described by electric field line distribution. See Figure 1 and Figure 2, respectively, for the electric field line distribution of point charge and parallel plate capacitance, in the figure, 10 Is the electric field line, 28 and 29 are point charges. To facilitate the discussion below, Figure 3 shows the electric field line distribution of a semi-circular planar capacitor. As can be seen from Fig. 2, the electric field lines 10 of the parallel plate capacitors are mainly distributed in the rectangular space between the two parallel plates. Therefore, when calculating the capacitance of the parallel plate capacitors, the influence of the electric field of the parallel plate edges can be ignored. The capacitance calculation formula of the plate capacitor: C=e*S/d. Similarly, as can be seen from Fig. 3, the electric field lines of the planar capacitor are mainly distributed in the approximately elliptical sphere space around the two planar electrode plates. Since the theoretical calculation of the plane capacitance is too complicated, it will not be discussed in detail here.

Referring to FIG. 3 and FIG. 4, the electric field line spatial distribution of the planar capacitor in the application environment according to the present invention is shown, and the two planar electrode plates 11, 12 are closely attached to the glass 9, as shown in FIG. 3 and FIG. The distribution shape of the electric field lines 10 can be seen that the approximate elliptical sphere space around the two planar electrode plates 11 and the electrode plates 12 can be divided into three different spaces due to the influence of different media: the inner surface of the automobile glass 9 is closely attached to The planar electrode plate 11 on the inner surface and the approximately semi-elliptical spherical space N1 below the electrode plate 12; the flat electrode plate 11 and the electrode plate 12 and the flat elliptical space N2 contained inside the automobile glass 9; near the outer surface of the automobile glass 9 The semi-elliptical space Nx formed. Due to the approximate semi-elliptical sphere space N1 and the flat elliptical space The medium of N2 is uniform air and glass, respectively, and its dielectric constant and volume can be considered as constant. The semi-elliptical space Nx is usually air. When other foreign objects enter, the dielectric constant and volume will change greatly. The semi-elliptical space Nx is our measurement space.

Based on the above discussion, referring to Figure 5, the equivalent capacitance model proposed by the present invention. Wherein, the parallel equivalent capacitance C3 is a constant capacitance determined by a semi-approximate elliptical sphere space N1 and a flat elliptical space N2, and the series capacitors C1 and C2 are crossed by the plane electrode above the outer surface of the automobile glass but enclosed on the outer surface of the automobile glass. The constant capacitance determined by the space inside, Cx is a variable capacitance formed by the semi-elliptical space Nx. The capacitance of Cx depends on both the dielectric constant of the foreign matter entering the semi-elliptical space Nx, the area covered by the foreign matter, and the thickness of the foreign matter formed in the semi-elliptical space Nx, which thickness can theoretically be equivalent to the pitch of the parallel plate capacitor.

Through the above discussion of the principle of the present invention, we can obtain the following two conclusions - 1. The planar capacitor proposed by the present invention is different from any other type of capacitive sensor in the past, including: variable area, variable pitch type, and variable Dielectric constant type, which is a comprehensive capacitive sensor that simultaneously senses changes in three parameters of area, pitch and dielectric constant.

2. The planar capacitor proposed by the invention can not only distinguish foreign objects near the surface of the automobile glass, but also can simultaneously sense the area and thickness of the foreign matter covered on the surface of the automobile glass covered by the sensor, which is impossible for the existing photoelectric sensor. .

Having explained the inventive principle of the present invention, a planar capacitive sensor fabricated by the above principle is given below.

Referring to FIG. 6 and FIG. 8, as a preferred embodiment of the present invention, two rectangular electrode plates 11 having a width of a=2 cm and a length of b=4 cm are processed by using a copper foil tape with a sticker on one side. 6厘米。 The gap between the two plates is 0. 6cm. The electrode plates 11, 12 are attached to the inner surface of the windshield 9 of the automobile, and are located behind the automobile rearview mirror 19 without affecting the driver's line of sight and being in the range of the wiper brushing range. Thereby two electrodes of the planar capacitor 1 are formed. Mounting on the inner surface of the windshield 9 of the car enables non-contact measurement. At the same time, the installation position of the planar capacitor 1 belongs to the working range of the wiper rain, not only detecting whether there is rain on the glass surface, but also detecting the effect of the wiper work. The distance between the plates 11, 12 is greater than the position of the plates Set the thickness of the glass. Thus, a large portion of the magnetic field formed is located outside the outer surface of the glass to form a semi-elliptical magnetic field space Nx for measuring rainwater.

Referring to FIG. 7 and FIG. 8, in the above embodiment according to the present invention, in order to eliminate the influence of temperature and electromagnetic on the planar capacitor 1, the present invention is provided with a planar capacitance compensator 2 in parallel behind the planar capacitor 1. The two plates of the planar capacitor compensator 2 are identical to the two plates of the planar capacitor 1, and the spacing is the same. Finally, the planar capacitor compensator 2 is identical in shape, size, and static capacitance value to the planar capacitor 1. In order to make the planar capacitance compensator 2 not sensitive to rain, a layer of insulating material 4 is disposed between the planar capacitor 1 and the planar capacitor compensator 2 to form a certain pitch. Therefore, the magnetic field space formed by the planar capacitance compensator 2 does not exceed the outer surface of the windshield of the automobile, that is, there is no magnetic field space Nx for measuring rainwater.

Referring to FIG. 6, the planar capacitor 1 and the planar capacitor compensator 2 are arranged in parallel in front and rear. The planar capacitor 1 can also be mounted on the interlayer of the front windshield 9 of the automobile during installation. The planar capacitance compensator 2 is located on the inner surface of the front windshield 9 of the automobile opposite to the position of the planar capacitor 1. However, it is also to be ensured that the magnetic field of the planar capacitance compensator 2 is located below the outer surface of the glass, i.e., there is no magnetic field space Nx for measuring rainwater.

Referring to Figures 10 and 11, in another preferred embodiment of the present invention, the planar capacitor compensator 2 and the planar capacitor 1 are mounted on the same plane of the front windshield 9 of the automobile. They are all located on the inner surface of the front windshield 9 of the car. One plate 21 of the planar capacitor compensator 2 is shared with one of the plates 12 of the planar capacitor 1, and the other plate 22 of the planar capacitor compensator 2 is located at one side of the common plate. The width is 0.2 cm, the length is 4 cm, and the gap with the common plate 12 is 0.1 cm. The total area of the two plates of the planar capacitor compensator 2 is 8.8 square centimeters. The total area of the two plates of the planar capacitor compensator 2 is smaller than the total area of the two plates of the planar capacitor 1 (16 square centimeters), and the spacing between the two plates of the planar capacitor compensator 2 is much smaller than The thickness of the glass 9 at the location. This ensures that the magnetic field of the planar capacitive compensator 2 is located below the outer surface of the glass 9, i.e., does not have the magnetic field space Nx for measuring rainwater. Referring to FIG. 12, in the embodiment of the present invention, the planar capacitor 1 and the planar capacitor compensator 2 are disposed in the same plane, and the planar capacitor compensator 2 may be disposed inside the planar capacitor 1. In still another aspect of the present invention, one of the two plates of the planar capacitor 1 is an annular plate 11 in which a circular plate 12 is disposed. Further, a small circular plate 22 is disposed in the circular plate 12 of the planar capacitor 1, so that the large circular plate 12 becomes a common plate, thereby constituting the planar capacitance compensator 2. The distance between the small circular plate 22 and the large circular plate 12 is much smaller than the thickness of the glass in which it is located, thereby ensuring that the magnetic field of the planar capacitive compensator 2 is located below the outer surface of the glass, that is, without measuring rainwater The magnetic field space Nx used.

In the above various embodiments of the present invention, the ultimate goal is to ensure that the magnetic field of the planar capacitive compensator 2 is located below the outer surface of the glass 9, that is, without the magnetic field for measuring rainwater, regardless of the embodiment. Space Nx. 'This is the only way to make the planar capacitor compensator 2 insensitive to rain, sensitive to temperature and electromagnetic interference signals, and a sensitive component that only detects the interference signal.

Referring to Fig. 13, in the embodiment of the present invention, the planar capacitor 1 and the plates of the planar capacitor compensator 2 are connected to the sensor detecting circuit 3 by shield wires 14, respectively. In order to prevent accidental damage, a conical plastic protective cover 24 is attached to the rear surface of the planar capacitor 1 and the planar capacitor compensator 2, and a conical plastic protective cover 24 is adhered to the inner surface of the windshield 9 of the automobile. In order to protect the shielded conductor 14, the shielded conductors 14 are led out through the plastic sleeve 13 on the upper side of the conical plastic protective cover 24 into the interlayer of the roof casing 17 and the roof trim 16, and the two shielded conductors 14 are electrically connected to each other. On the circuit board 15 in the roof of the roof casing 17 and the roof trim 16, the circuit board 15 is electromagnetically shielded and protected by a plastic casing 23 with a shield, and the digital output signal of the sensor is sent to the automatic through the shielded LIN bus cable 18. The control unit of the wiper system.

Referring to FIG. 14, in the above embodiment of the present invention, the sensor detecting circuit 3 includes a signal generator 31, a program-controlled analog signal amplifying and filtering circuit 32, a differential circuit 33, an analog-to-digital conversion circuit 34, and a microprocessor 35. The signal generator 31 generates a sine wave test signal 36 of the access plane capacitor 1 and the planar capacitance compensator 2, when the test signal 36 flows through The planar capacitor 1 and the planar capacitor compensator 2 are changed by the influence of the external environment, and the two changed test signals 36 are respectively input into the programmable analog signal amplification and filtering circuit 32, and after amplification and filtering, two DCs are generated. The voltage signal 37, after the two DC voltage signals 37 are differentially processed by the difference circuit 33, generates a differential signal, and the differential signal is converted into a digital signal via the analog-to-digital conversion circuit 34 to receive by the microprocessor 35. The digital signal, which is digitally filtered, digitally linearized, and digitally adaptively adjusted by the microprocessor 35 to form a digital output control signal of the sensor and sent to a shielded LIN (Local Interconnect Network) bus interface. Circuit 38 is then routed through shielded LIN bus cable 18 to the control unit of the automatic wiper system. After the wiper works, the device continues to detect the glass surface and form a feedback signal to further control the operation of the wiper to form a closed-loop control system, so that the device controls the operation of the wiper according to the size of the raindrop. The test signal given by the present invention may also be a square wave signal or a triangular wave signal. The frequency of the test signal 36 may be between lOOkHZ- lOOOkHZ, the present embodiment is employed in the frequency of 230KHZ, 'static capacitance value of the capacitor 1 plane and the planar capacitive compensator 2 in the 50- 400 _P f between. The capacitance value used in this embodiment is 220 pf.

Referring to FIG. 15, in another embodiment of the present invention, the sensor detection circuit 3 includes a signal generator 31, a programmable analog signal amplification and filtering circuit 32, an analog to digital conversion circuit 34, and a microprocessor 35. The signal generator 31 generates a test signal 36 for accessing the planar capacitor 1 and the planar capacitance compensator 2, which is changed by the external environment when the test signal 36 flows through the planar capacitor 1 and the planar capacitive compensator 2. The two changed test signals 36 are respectively input to the programmable analog signal amplification and filtering circuit 32, and after being amplified and filtered, two DC voltage signals 37 are generated, and the DC voltage signals 37 are respectively passed through the analog to digital conversion circuit 34. Converted into two digital signals, the microprocessor 35 receives the two digital signals, performs differential operations on the two digital signals, and digitally filters and digitally linearizes the differentially processed digital signals in the microprocessor 35. Processing and digital adaptive algorithm adjustment to form the sensor's digital output control signal sent to the shield LIN (Local Interconnect Network) connection The port circuit 38 is then routed through the shielded LIN bus cable 18 to the control unit of the automatic wiper system. After the wiper works, the device continues to detect the glass surface and form a reverse The feed signal further controls the operation of the wiper to form a closed loop control system, so that the device controls the operation of the wiper according to the size of the raindrop.

In the above embodiment of the present invention, the conductive material used for the planar capacitor 1 and the plate of the planar capacitor compensator 2 is copper, aluminum, silver, conductive rubber, conductive plastic, conductive adhesive or transparent conductive film. The plates required for the planar capacitor 1 and the planar compensation capacitor 2 are formed on the inner surface of the automobile glass 9 by a plurality of mounting methods such as: pasting, pressing, and spraying, and the plates may be many Shapes such as rectangles, rings, scallops, triangles, or polygons. The annular plate is shown in Figure 9. The installation should ensure that the plates of the planar capacitor 1 are in close contact with the inner surface of the glass 9 to avoid the influence of the air gap on the sensor. Metal plating on the glass surface is the best choice. Experiments have shown that the total area of the plates of the planar capacitor 1 can be less than 100 cm 2 , but the total area of the two plates of the planar capacitor 1 is preferably 10-20 cm 2 in terms of cost saving and use effect. The planar capacitor compensator 2 has a total area of 5-11 square centimeters.

The following is a method for detecting the environmental change of the windshield surface of a car using the above device:

According to the detection method provided by the present invention, the process is as follows:

a, initialize the sensor;

b. The signal generator 31 in the sensor generates a test signal 36, which is transmitted to the planar capacitor 1 and the planar capacitor compensator 2, respectively;

c. respectively detecting a change caused by the influence of the external environment when the test signal 36 passes through the planar capacitor 1 and a change caused by the interference signal when the test signal 36 passes through the planar capacitance compensator 2;

d. Perform differential operation on the detected two change test signals 36;

f, transmitting control signals to the device;

The initialization of the sensor of the invention is based on the material and thickness of the automotive glass, the plane electricity The area of the sensing element of the container 1 and the mounting method, ambient temperature, and humidity conditions, and the static initial value of the sensing element of the planar capacitor 1 is detected and set. Since the dielectric constants are different due to different substances, the detecting device can set different initial values according to different substances to determine which substances adhere to the glass surface. For example, when water adheres to the glass surface where the planar capacitor 1 is located, the capacitance value of the planar capacitor 1 changes, and the amount of change of the capacitor at this time is set as a criterion for judging that water adheres to the surface of the glass.

The method of the present invention is realized by providing a planar capacitor 1 and a planar capacitance compensator 2 on the inner surface of the windshield 9 of the automobile, the two plates 11, 12 of the planar capacitor 1 being placed on the same plane, As a sensitive element for detecting a change in rainwater on the surface of the windshield 9, a signal of the change in the capacitance Cx caused by the magnitude of the rainwater of the planar capacitor 1 is transmitted to the sensor detecting circuit 3. The two plates 21, 22 of the planar capacitance compensator 2 are also placed on the same plane. Since the mounting position or shape is different from that of the planar capacitor 1, the size of the rain does not affect its capacitance. Therefore, it can only detect changes in temperature and electromagnetic interference to its capacitance, and transmits a change signal to the sensor detecting circuit 3. The sensor detecting circuit 3 performs a differential operation based on the detected two change test signals, and generates a control signal for controlling the operation of the device based on the result of the difference operation. Since the test capacitors of the planar capacitor 1 and the planar capacitor compensator 2 are affected by temperature and electromagnetic interference, the changes of the test signals are simultaneously synchronized and the amplitudes are approximately equal. For the rain change, only the test signal of the planar capacitor 1 changes. According to the above characteristics, after the differential operation, the effects of temperature and electromagnetic interference can be effectively eliminated. The detection accuracy of the sensor is improved, and the ultimate object of the invention is achieved.

Claims

Claim

A planar capacitive sensor comprising a planar capacitor (1) mounted on a windshield (9) of a vehicle and a sensor detection circuit coupled to said planar capacitor (1)

(3) the planar capacitor (1) is a sensitive component of the sensor, wherein two plates of the planar capacitor (1) are placed on the same plane, and the sensor detecting circuit (3) detects the planar capacitor ( 1) a change in capacitance caused by the environment, and a control signal for controlling the operation of the wiper device according to the detected change in capacitance, wherein: the sensor detection circuit (3) is further connected with a plane for canceling the interference signal a capacitor compensator (2), the two plates of which are placed on the same plane, the planar capacitance compensator (2) only serves as a sensitive component for detecting an interference signal, and the sensor detection circuit (3) detects the planar capacitance compensation The device (2) changes the capacitance caused by the disturbance signal, and compensates for the change in capacitance caused by the environmental impact of the planar capacitor (1) according to the detected capacitance change.

The planar capacitive sensor according to claim 1, characterized in that: the planar capacitance compensator (2) and the planar capacitor (1) are arranged in parallel on the windshield (9) of the automobile.

The planar capacitive sensor according to claim 1 or 2, wherein: the planar capacitor (1) is located in an interlayer of a windshield (9) of the automobile, and the planar capacitive compensator (2) is located The planar capacitor (1) is positioned opposite the inner surface of the automotive windshield (9).

The planar capacitive sensor according to claim 1 or 2, wherein: the planar capacitor (1) is in close contact with the inner surface of the windshield (9) of the automobile, and the planar capacitor compensator (2) in said plane capacitor (1) behind, and by a layer of insulating material (4) is formed with a spacing between _ώ (1) the planar capacitor

The planar capacitive sensor according to claim 1, characterized in that: the planar capacitance compensator (2) is mounted on the same plane as the planar capacitor (1).

6. The planar capacitive sensor according to claim 5, wherein: said plane A capacitor compensator (2) and the planar capacitor (1) are mounted on the inner surface of the windshield (9) of the automobile.

7. A planar capacitive sensor according to claim 5, characterized in that said planar capacitive compensator (2) is located in or immediately adjacent to said planar capacitor (1).

8. A planar capacitive sensor according to claim 5 or 6 or 7, characterized in that - said capacitance compensator (2) shares one of the plates with said planar capacitor (1).

The planar capacitive sensor according to claim 5 or 6 or 7, wherein - the total area of the two plates of the planar capacitance compensator (2) is smaller than the total of the two plates of the planar capacitor (1) The area, and the spacing between the two plates of the planar capacitor compensator (2) is smaller than the thickness of the glass at the location where the spacing between the two plates of the planar capacitor (1) is equal to or greater than the thickness of the glass at the location .

The planar capacitive sensor according to claim 1, wherein: the planar capacitor (1) and the planar capacitor compensator (2) are made of a conductive material of copper, aluminum, silver, or conductive. Rubber, conductive plastic, transparent conductive film or conductive adhesive; bonded, pressed or sprayed on the inner surface of the windshield (9) of the car.

The planar capacitive sensor according to claim 1, wherein: the planar capacitor (1) and the planar capacitor compensator (2) have rectangular plates, a ring shape, a sector shape, a triangle shape or a polygonal shape. The total area of the two plates of the planar capacitor (1) is 10-20 square centimeters, and the total area of the two plates of the planar capacitor compensator (2) is 5-11 square centimeters.

The planar capacitive sensor according to claim 1, wherein: said sensor detecting circuit (3) comprises a signal generator (31), a programmable analog signal amplifying and filtering circuit (32), and a differential circuit (33). , an analog-to-digital conversion circuit (34), a microprocessor (35), the signal generator (31) generates a test signal (36) for the access plane capacitor (1) and the planar capacitance compensator (2), The test signal (36) flows through the planar capacitor (1) and The planar capacitance compensator (2) is changed by the influence of the external environment, and the two changed test signals (36) are respectively input into the program-controlled analog signal amplification and filtering circuit (32), and after amplification and filtering, two DCs are generated. a voltage signal (37), the two DC voltage signals (37) are differentially processed by the difference circuit (33) to generate a differential signal, and the differential signal is converted into a digital signal via the analog-to-digital conversion circuit. The microprocessor receives the digital signal and processes the digital signal to form a sensor digital output signal that controls the operation of the device.

13. The planar capacitive sensor according to claim 1, wherein: said sensor detecting circuit (3) comprises a signal generator (31), a program-controlled analog signal amplifying and filtering circuit (32), and an analog-to-digital conversion circuit ( 34) a microprocessor (35), the signal generator (31) generating a test signal (36) for the access plane capacitor (1) and the planar capacitance compensator (2), when the test signal (36) Flowing through the planar capacitor (1) and the planar capacitor compensator

(2) The time is changed by the external environment, and the test signals (36) after the two changes are respectively input into the program-controlled analog signal amplification and filtering circuit (32), and after amplification and filtering, two DC voltage signals (37) are generated. The two DC voltage signals (37) are respectively converted into two digital signals via the analog-to-digital conversion circuit (34), and the microprocessor (35) receives two of the digital signals, and performs differential operations on the two digital signals. And based on the result of the differential operation, a digital output signal of the sensor that controls the operation of the device is formed.

The planar capacitive sensor according to claim 12 or 13, wherein: the planar capacitor (1) is installed in an area where the automobile wiper works, and the device continues to detect the glass surface while the device is operating. And form a feedback signal to further control the operation of the equipment to form a closed-loop control system.

The planar capacitive sensor according to claim 12 or 13, wherein - the test signal (36) is a sine wave signal, a square wave signal or a triangular wave signal, and the frequency of the test signal (36) is lOOkHZ — 1000kHZ, the planar capacitor (1) and the planar capacitor compensator (2) have a static capacitance between 50 and 400 pf.

16. A method of detecting environmental changes in a windshield of a vehicle using the sensor of claim 1 wherein the process is as follows:

a, initialize the sensor;

b. The signal generator (31) in the sensor generates a test signal (36), and the test signal (36) is respectively transmitted to the planar capacitor (1) and the planar capacitor compensator (2);

c. respectively detecting the change of the test signal (36) caused by the external environment through the planar capacitor (1) and the test signal (36) being affected by the interference signal when the planar capacitance compensator (2) The change;

d. Perform differential operation on the detected two change test signals (36);

f, transmitting control signals to the device;

17. A method of detecting environmental changes in a windshield of a vehicle as claimed in claim 16 wherein: said sensor is mounted in the area in which the automotive wiper operates.