JP3802897B2 - Vehicle glass breakage alarm device - Google Patents

Description

  The present invention relates to a vehicle antitheft device that detects a change in micro atmospheric pressure in a vehicle due to breakage of a glass window of the vehicle using a pressure sensor.

Conventional anti-theft devices and anti-roughing devices for vehicles are roughly divided into mechanical devices that make it impossible to operate by fixing pedals, levers, steering, etc., necessary for driving the vehicle, and various sensors. There are electronic devices that generate alarm signals.
1. JP 2000-386728 A 2. JP-A-5-128200 3. JP 2003-85660 A

  A typical example of an electronic device is a method of detecting an impact (body vibration detection) sensor attached to the vehicle body and detecting the vibration applied to the vehicle body. However, when the detection sensitivity is increased, a person touches the vehicle. There were many so-called malfunctions that responded to the vehicle alone or operated when the vehicle passed nearby.

As another typical example of an electronic device, there is a device that uses an audio band microphone to detect abnormal sounds such as a hitting sound applied to a vehicle body or glass breakage, but this device also increases the sensitivity of the microphone. In addition, there is a drawback in that it malfunctions in response to natural wind and surrounding sounds that enter from the air intake port of the vehicle.
There is also a problem that the sound of crack progress due to glass breakage cannot be distinguished from the ambient sound.

As another example of the electronic device, there is a method in which a microphone capable of detecting an ultra-low frequency below the audible band is installed in a vehicle, and a pressure change generated in the vehicle is detected when the door is opened and closed. Proposed.
However, this method is also likely to malfunction in vehicles with low airtightness.

If the sensitivity of the sensor or microphone is lowered in order to avoid malfunctions that are common disadvantages of electronic devices as described above, it will not be possible to detect if the thief is careful and quiet.
Therefore, in order to obtain a sufficient anti-theft effect, it is necessary to use an electronic device and a mechanical device in combination.

In addition, as a method for detecting the breakage of the window glass, there is a method in which a transparent conductive pattern is mounted on the glass surface and an attempt is made to use the change in electrical characteristics of the glass surface due to the breakage of the glass. (Japanese Patent Laid-Open No. 2003-85660)
However, if such an element is attached to the glass surface, it cannot withstand the friction caused by opening / closing or wiping the window.
In order to prevent this, it is conceivable to embed the glass inside the glass, but this is not a realistic method in terms of production process and cost.

  The present invention focuses on the phenomenon that when the tempered glass used in a vehicle is broken, the glass expands to the outside of the vehicle at the same time as cracks generated at a high speed, thereby abruptly occurring in the vehicle about 25 to 42 mSec. A minute negative pressure of a width is detected by a pressure sensor such as a piezoelectric microphone or an omnidirectional condenser microphone, and a theft alarm signal is generated.

  In addition, the phenomenon that 300 to 600 Hz vibration lasts for about 10 to 25 mSec at the time of cracking is captured by the same sensor, and by combining this signal with the negative pressure generation signal, the accuracy of glass breakage detection is increased and malfunctions are caused. It is something to prevent.

  According to the vehicle antitheft device of the present invention, an alarm signal is generated only by detecting a specific pressure change that occurs only in an abnormal situation such as a glass breakage of a vehicle, so that a general pressure change is detected. Compared with the method, the risk of malfunction can be reduced.

  In addition, it is possible to reduce the malfunction of the alarm signal by capturing the unique sound at the time of crack occurrence with the microphone and generating the alarm signal only when both signals due to pressure change are observed. Become.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a graph in which when a crack occurs in a glass of a sealed vehicle, the pressure change in the vehicle is measured by a pressure sensor and the output is displayed on a waveform analyzer.
FIG. 1A shows the case where cracks occur in the side window (largest area window) glass.
FIG. 1B shows a case in which a crack has occurred in the glass of the rear fitting window (smallest area window).
In either case, the vertical axis represents voltage millivolts (mV), and one scale is 80 mV. The horizontal axis represents elapsed time in milliseconds (mS), and one scale is 100 mS.
The positive side indicates that a positive pressure has occurred with the zero voltage line as the boundary, and the negative side indicates that a negative pressure has occurred.

In FIG. 1 (common to both A and B), when a crack occurs in the glass, the crack spreads instantaneously over the entire glass surface as a characteristic of the tempered glass used in the vehicle.
In general, glass for vehicles is sealed with an elastic body such as rubber in order to keep watertight.
On the other hand, the tempered glass is made so as to keep the original shape as much as possible even if a crack occurs for safety, so that the expansion phenomenon occurs toward the outside of the vehicle at the same time as the crack occurs.

Therefore, a steep negative pressure is generated inside the vehicle at the point b, and once counterbalanced with the external air pressure at the point c, the positive pressure reaches the maximum value at the point d.
Thereafter, after a slight fluctuation is repeated, it converges to a zero level, that is, a state in equilibrium with the external pressure.

In FIGS. 1A and B, a case where a crack occurs in the side window glass and the rear-fitting triangular window is illustrated, but almost all of these relatively small windows are divided in the case of vehicle theft and roughing on the vehicle. It is rare that a large laminated glass such as a windshield is broken.
Regardless of the type and size of the vehicle, when these windows cracked, a similar wave shape was observed.
In addition, the time w from the occurrence of a crack (point a) to the return to the zero level (point c) is within a range of a minimum of about 25 mS and a maximum of about 42 mS regardless of the type of vehicle or the size of the window. Confirmed.

  Therefore, it is possible to measure the initial negative pressure b and the negative pressure maintenance time w, and detect the occurrence of cracks by their mutual relationship.

Next, the sound generated when a crack occurs will be described.
FIG. 2 is a graph in which a high-frequency sound of 300 Hz or higher is picked up and displayed on a waveform analyzer when a crack is generated in a triangular window by a sensor in a vehicle.
In the graph, the vertical axis indicates voltage with a scale of 40 mV, and the horizontal axis indicates time with a scale of 10 mS.
It is a period of about 10 to 25 mS that a sound having a certain intensity (output of ± 20 mV or more) is generated from the time of occurrence of a crack at point a in FIG. 2 regardless of the size of the glass.
The frequency is 300 to 600 hertz.

FIG. 3 shows a table of results obtained by measuring the duration of the negative pressure width W and the crack progress sound of 20 mV or more with respect to a commercially available general passenger car (including a light vehicle).
Vehicle types A to J are abbreviations for the vehicle to be inspected.
The remarks column indicates which window of the vehicle has been broken.
As a result, in these 10 models, the duration W of the negative pressure was 25.5 mS at the shortest, 42 mS at the longest, and 31.6 mS on average.
In addition, the time for observing a crack progress sound of 20 mV or higher at a frequency of 300 to 600 Hz was 11 mS at the shortest, 24.5 mS at the longest, and an average of 16.8 mS.
Therefore, when a period of a certain level of negative pressure b and a certain width w is detected by the pressure sensor and a sound of 300 to 600 Hz is detected by the microphone for about 10 to 25 mS seconds, it is determined that a crack has occurred. If an electric circuit is set in advance, malfunction can be prevented as compared with a case where determination is made only by the generation of negative pressure.

By the way, as described in the section [0003], in an actual use situation, a parked vehicle resonates and resonates with vibrations from a car, train, airplane, etc. that passes nearby, and is affected by so-called low-frequency pollution.
The low frequency has a long wavelength, the acoustic resistance is low in tube resonance such as tunneling, and the resonance sharpness Q far exceeds π / 2.
In addition, a three-dimensional crossing bridge or the like cannot reduce the spring rigidity in order to ensure the strength against a heavy vehicle, and when passing through a heavy vehicle, although Q decreases, vibrations cannot be braked to π / 2 or less.
Therefore, the positive pressure side signal immediately before the negative pressure side signal is at least 37% (about one third or more).
The apparatus according to the present invention also knows the characteristics of low-frequency pollution and eliminates the influence thereof, so that malfunction can be prevented more reliably.

FIG. 4 is a graph in which the output when a microphone picks up the sound when another vehicle passes near the vehicle parked on the three-dimensional intersection road is displayed with a waveform analyzer.
The vertical axis represents one scale of 40 mV, and the horizontal axis represents one scale of 250 mS.

As is clear from FIG. 3, the vibration becomes stronger as the passing vehicle approaches, and the vibration becomes weaker as the vehicle goes farther.
A part of the waveform of the negative pressure in this may include a waveform very similar to the waveform of the negative pressure caused by the crack.
However, the fundamental difference is that the pressure waveform caused by cracks always appears steeply on the negative side, whereas the positive side noise always exists before the negative side of the vehicle passing noise. .

Therefore, the pressure sensor for detecting negative pressure due to cracks provided inside the vehicle is about 3 minutes of the negative pressure (b value in FIG. 1) generated when the triangular window with the smallest glass area cracks. If one or more positive pressure side signals are first detected, it is possible to recognize that the subsequent negative pressure signal is not due to glass cracks, thereby preventing malfunction due to vibration of the passing vehicle. it can.
In the example of FIG. 1B, the negative pressure signal due to the crack is about 200 mV, and the negative pressure duration w is within 35 ms. Therefore, immediately after the detection of the positive pressure side signal of 70 mV or higher, the negative pressure signal is maintained for about 42 ms or longer. It is sufficient to set the dead time of the pressure sensor so as not to detect.

FIG. 5 is a chart showing a program for setting the dead time in the alarm device for detecting cracks.
When the alarm device using the pressure sensor is turned on (started), the pressure sensor enters a negative pressure detection state and also enters a state of detecting ambient noise.
When a positive level signal equal to or higher than a certain level is detected in ambient noise (YES), the signal is fed back to the pressure sensor and instructed to execute a dead time of 42 mS or more.
When there is no positive level of a certain level (NO), the normal standby state is continued.
When a negative level of a certain level or more is detected in this state, the negative pressure width (time) is detected, and the negative level returns to the zero level, so that the negative pressure width w (w shown in FIG. 1). Determine.
When w is 42 mS or less and the negative level is 70 mV or more, it is determined that there is a negative pressure due to a crack, and an alarm is activated.
Note that various examples of alarms such as sound, light emission, and signal transmission to an external receiving device can be considered.

A is a graph showing a change in pressure generated when a crack occurs in the side window glass. B is a graph showing the pressure change that occurs when a triangular window cracks A graph showing the sound produced when a crack occurs A diagram showing the time of negative pressure and sound generated when a crack occurs A graph showing the sound of a vehicle passing outside the vehicle Chart representing the program

Claims (3)

A pressure sensor is disposed inside the vehicle having a window of tempered glass and the periphery of the tempered glass is sealed with an elastic body,
When a crack occurs in the tempered glass when the vehicle is sealed,
Detect both steep negative pressure and crack sound generated inside the vehicle at the same time as the crack is generated as an electrical signal with the pressure sensor,
A glass breakage alarm device for a vehicle, which generates an alarm in response to the electric signal.   2. The vehicle glass breakage alarm device according to claim 1, wherein the negative pressure and crack sound detected by the pressure sensor are 25 ms after the occurrence of the crack.   2. The vehicle glass breakage alarm device according to claim 1, wherein the pressure sensor detects a change in external sound and pressure entering the vehicle interior, and a positive signal level of an external sound or pressure electrical signal is a constant value. When the above is exceeded, the vehicle glass breakage alarm device is set so that the recognition of the negative pressure signal is interrupted for 42 ms or more thereafter.

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