CN2199099Y - Vehicle anti-theft alarm device - Google Patents

Abstract

An anti-theft alarm device for vehicle is aimed at detecting pressure change and giving alarm when someone breaks through the cab. The sensor activates the annunciator when detecting a pressure change. However, since such sensors are so sensitive that pressure changes occurring when the door is closed are also detected, false positives result. In order to avoid this error, a second sensor is additionally arranged in the alarm circuit, which second sensor is arranged outside the vehicle. If the pressure change is detected by the two sensors at the same time, the alarm system can not be activated. Only if the sensor in the vehicle detects a pressure change will the alarm system be activated.

Description

The utility model relates to an anti-theft alarm device for vehicles, especially an alarm device which is designed to be used together with automobiles, can minimize false alarms, and can only activate when someone tries to break into the vehicle without authorization.

It is very common for traditional electronic alarm devices to be used as anti-theft devices. This type of anti-theft device is often used in conjunction with automobiles. After being activated, the anti-theft alarm device can perform various required functions. For example, when the alarm device is activated, it can cause annunciators such as whistles, horns and/or flashing lights to be activated. In addition, after the alarm device is activated, it can also disable the starting circuit of the car.

A commonly used alarm device in the past is to install a sensor in the electronic circuit. When the sensor detects a change in pressure, even a slight pressure change will trigger the circuit to start. For example, a car horn produces a series of beeping sounds, or Make the lights flash and go off. The sensor of the alarm device is located in the cab of the car. If the alarm device is set, it will be activated when the door is opened. A broken window will also activate the alarm. In fact, the sensors are so sensitive that even someone tapping hard on the window will trigger the alarm. The reason is that when the car window is knocked heavily, it is vibrated enough to change the air pressure in the cab, and the sensor will detect it and activate the alarm device.

For alarm devices to function properly, these sensors must be highly sensitive. However, this also means that any changes in pressure throughout the car are detected by the sensors. As a result, the alarm device is often falsely activated due to pressure changes outside the vehicle. Parking a car in a garage is a good example of what can cause this false actuation, since the act of closing the garage door creates a change in pressure sufficient to activate the alarm. In addition, if the car is parked in the garage and the alarm device is set at the same time, the action of opening the door and entering the garage will also cause a change in pressure sufficient to trigger the alarm device.

Therefore, it is desirable to install a component in the induction anti-theft alarm device so that the alarm device will not be activated when the pressure difference in the surrounding environment of the automobile occurs. In order to avoid above-mentioned errors, the utility model adds a second sensor in the alarm circuit, and this second sensor is located on the outside of the automobile, such as in the engine room. If a pressure change is detected by these two sensors at the same time, the alarm system will not be activated. The alarm system is activated only when sensors in the vehicle detect a change in pressure.

The main purpose of this utility model is to provide a car anti-theft alarm system that can eliminate false alarms, so that when the alarm system is triggered, it is a real situation that someone is trying to break into the car without authorization.

Another object of the present invention is to provide a car alarm system that can be manufactured at a reasonable cost, and thus can be sold to consumers at a fairly reasonable price.

Fig. 1 is the schematic diagram of the general automobile that alarm system of the present utility model is housed, shows that this car is parked in the garage;

Fig. 2 is the circuit block diagram of the warning system of the present utility model; And

FIG. 3 is a schematic block diagram of the alarm system circuit shown in FIG. 2 .

Referring to the drawings, a typical garage 10 having a floor 12 is shown in longitudinal section. The garage 10 is usually attached to a house (not shown), and an access door 14 is provided between the parking space 16 of the garage 10 and the house. The garage door 18 can be used to close the parking space 16, and the opening and closing of the garage door 18 is accomplished by remote control of the garage door operating mechanism 20. A motor vehicle 22 can be parked on the floor 12 of the parking space 16 . Car 22 includes a cab. Inside the cab is an internal sensor 24 and its associated circuitry. In addition, the car 22 also includes an engine room, and an external sensor 26 and its associated circuits are located in the engine room.

Sensors 24, 26 and their associated circuits are combined to form the vehicle anti-theft alarm device of the present utility model. The utility model can also be used independently. However, it is also often used in conjunction with another type of alarm system installed in the vehicle 22 . For example, if someone jacks up the car with a jack and the wheels 28 are unloaded, the alarm system of the present utility model cannot be detected. Therefore another type of alarm system (not shown) must be installed on the automobile 22 to detect such unauthorized theft.

The utility model is designed to be connected with a conventional 12 volt storage battery (not shown) of the automobile 22 . The battery supplies electricity to connection point 32 via diode 30 . The connection point 32 is grounded via a capacitor 34 . The purpose of using the capacitor 34 is to keep the voltage in the connection point 32 at 12 volts, even if the battery of the automobile 22 consumes too much power, the voltage in the connection point 32 will not drop below 12 volts. Both diode 30 and capacitor 34 are part of a 2 volt DC supply 36 .

The connection point 32 is connected to a reference voltage generator 38 . The signal from connection point 32 is then passed via resistor 40 to a positive terminal 42 of amplifier 44 . The function of resistor 40 is to act as a current limiting resistor for diode 54 . Diode 54 is connected between connection point 32 and ground. The voltage supplied to the positive terminal 42 is approximately 0.6 volts. A negative terminal 46 of amplifier 44 is connected to resistors 48 and 50 via an output connection point 52 of amplifier 44 . The purpose of using capacitor 56 is to maintain the voltage in connection point 52 at 1 volt.

The output reference voltage is supplied from connection point 52 to connection point 58 , and then supplied to an external low-pass amplifier 64 via an internal low-pass amplifier 60 and connection point 62 . The reference voltage sent from connection point 58 is then supplied to the positive terminals of amplifiers 66 and 68 . Sensor 24 then supplies an output to the negative terminal of amplifier 66 via connection point 70 . Connected between connection point 70 and output connection point 72 of amplifier 66 is a gain control circuit comprising a capacitor 74 and a resistor 76 . The output signal at junction 72 is also around 1 volt, and this signal is passed through a low pass filter formed by capacitors 78, 80 and resistor 82. The low pass filter only passes the AC signal through resistor 84 which, together with resistor 86 and capacitor 88, sets the gain of second stage amplifier 68 . This signal is introduced into the negative terminal of amplifier 68, which produces a 5 to 10 volt signal from output connection point 90 of amplifier 68.

The output voltage developed at connection point 90 is introduced into the negative terminal of amplifier 94 via an input resistor 92 . In addition, the signal generated by the connection point 90 is also transmitted through a fixed value resistor 96 and an adjustable resistor 98 acting as a potentiometer. A signal is input from potentiometer 98 to the positive terminal of amplifier 94 . The charge supplied to amplifier 94 is held for a brief period of one or two seconds by means of resistor 100 and capacitor 102 . In addition, the resistor 100 and the capacitor 102 also have the function of filtering noise.

The output of amplifier 94 is directed to connection point 104 via diode 106 and fixed value resistor 108, wherein resistor 108 cooperates with resistor 110 and capacitor 112 to hold the charge for a brief period of time. This charge is supplied to the positive terminal of amplifier 114 of voltage comparator 116 . Amplifier 114 produces an output signal in connection point 118 only if its positive terminal is higher than its negative terminal. The negative terminal of amplifier 114 is connected to connection point 120 . The signal at connection point 120 is then responsive to the signal of the external or second sensor 26 provided on the external low pass amplifier circuit 64 .

If the sensor 26 senses pressure, it sends a signal to the negative terminal of the amplifier 122 . The positive terminal of the amplifier 122 is connected to the connection point 58 via the connection point 124 . In addition, the connection point 124 is also connected to the positive terminal of the second-stage amplifier 126 . If the sensor 26 detects a pressure difference, it will send a high level signal to the amplifier 122, and the positive terminal of the amplifier will also receive a high level signal. As a result, there is no output signal at junction 128 and the negative terminal of amplifier 126 . Since the amplifier 126 receives a high signal at its positive terminal, a high signal is generated at the output connection point 130 of the amplifier 126 . This high level signal is maintained in capacitor 130 for a period of time using resistor 132 , resistor 134 , and capacitor 136 . Resistors 132 and 134 are connected to the negative side of amplifier 138 and a high level signal is generated at output connection point 140 because the high level signal is sent to the positive terminal of amplifier 138 . The charge transferred from the output terminal 140 to the connection point 120 is also held by the resistor 142 and the capacitor 144 for a period of time.

The diode 146 charges the capacitor 144 instantaneously without delaying the charging by the signal via the resistor 142 . A high level signal at junction 120 is higher than a high level signal at junction 104 leading to the positive side of amplifier 114 . This means that the same pressure will be detected by both sensors 24 and 26 at the same time. Therefore, no output signal is passed to connection point 118, nor can it be connected to transistor 150 via resistor 111 and diode 148. In this way, the triode 150 will not be triggered, and the annunciator 152 will not be activated. A typical annunciator is a sounding device such as a whistle or horn, or it may be an annunciator such as a strobe light. The annunciator 152 is connected to the transistor 150 through a connection point 154 . The transistor 150 and the diode 148 form an output device 156 . This output device outputs the signal generated by the voltage comparator 116 .

Assume that sensor 24 senses a pressure and that pressure results in a high level signal being sent to the positive terminal of amplifier 114 . Assume further that sensor 26 detects no pressure and therefore sends a low level signal to the negative terminal of amplifier 122 . However, if a high level signal is applied to the negative terminal of amplifier 122 and the signal is amplified by capacitor 158 and resistor 160, the signal will be introduced into junction 128 and passed through capacitors 162, 164 and resistor 166. A low-pass filter is formed which is substantially the same as the low-pass filter formed by capacitors 78, 80 and resistor 82 described above. The signal then passes through resistor 168 , which may cooperate with capacitor 170 and resistor 172 to establish the gain effect of amplifier 126 . However, there are now two high level signals to the two terminals of amplifier 126 and one low level signal from connection point 130 to the positive terminal of amplifier 138 via resistor 174 . The output from amplifier 138 in connection point 130 is also at a low level like this low signal going into connection point 120 and thus goes to the negative terminal of amplifier 114 . Since the signal transmitted to the positive side of the amplifier 114 is at a high level, an output signal is provided at the connection point 118, which causes the transistor 150 to switch to the on position. After the triode is switched, the trigger annunciator 152 will be activated.

In summary, the present invention utilizes pressure change as its inducing medium. There is a sensor in the cab of the car. When the sensor detects a change in pressure, it activates the alarm system. There is also a second sensor located outside the cab, such as in the engine room, but still on the body of the car. When both sensors detect a change in pressure, the alarm system is not activated. As a result, a false alarm situation caused by a change in pressure outside the vehicle, such as when the garage door is closed and the door is opened to enter the garage from a room, can thus be prevented. The alarm system will only be triggered when the sensor in the cab detects a change in pressure, but the external sensor does not detect this change.

Claims (3)

1. An anti-theft alarm device for a vehicle, which includes a first sensor which is extremely sensitive to air pressure changes in the cab, and which is connected to an annunciator through a circuit, and is characterized in that it also includes: The second sensor, the second sensor is connected to the circuit, the second sensor is also extremely sensitive to changes in air pressure, and is installed outside the cab of the car, if the first and second sensors are simultaneously When it is detected that the air pressure changes, the annunciator will not be actuated, and only when the first sensor detects an air pressure change but the second sensor does not detect an air pressure change, the annunciator is actuated. 2. The vehicle anti-theft alarm device according to claim 1, characterized in that said automobile comprises an engine compartment, which is located outside said driver's cab, and said second sensor is installed on Inside the engine room. 3. The vehicle anti-theft alarm device according to claim 1, characterized in that the sensitivity of the first sensor can be adjusted.

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