JPH02283548A - Burglar alarm device for vehicle - Google Patents

Abstract

PURPOSE:To watch a burglar from the time immediately after a parking even though a vehicle is parked on a sloped ground by providing an inclination detecting device, an inclination change detecting device, an alarm device, and an initiating device to reset the output of the inclination change detecting device at the parking starting time of the vehicle. CONSTITUTION:When a vehicle is parked on a sloped ground, the inclination change is detected at the starting time of the parking, the output of an inclination change detecting device 20 is increased suddenly, and it is soon reduced to a normal value, but the change is made slowly. This is because a burglar who tries to incline the vehicle by a slow jacking-up is made as the object of detection, and the time constant of the C and R is set larger for such a purpose. Since the residual charge of a capacitor C is discharged forcibly by the switch of an initiating device 40 at the starting of the parking, and the output of an amplifier 31 is returned to a normal value instantly, the burglar watching can be carried out from the time immediately after the starting of the parking even though the vehicle is parked on a sloped ground.

Description

[Detailed Description of the Invention] [Summary] Regarding a vehicle theft alarm device that detects changes in the inclination of a vehicle in an alternating current manner, the residual output of the inclination change detection means is prevented from interfering with theft detection at the start of parking for a long time. Inclination detecting means mounted on a vehicle to detect the degree of inclination of the vehicle; inclination change detecting means detecting changes in the inclination of the vehicle in an alternating current manner from the output of the inclination detecting means; and the inclination change detecting means The vehicle is configured to include an alarm means that issues an alarm when the output of the means exceeds a certain value, and an initialization means that forcibly resets the residual output of the slope change detection means when the vehicle starts parking.

[Industrial Field of Application] The present invention relates to a vehicle theft alarm system that detects changes in the inclination of a vehicle in an alternating current manner.

Tire theft by jacking up a parked vehicle or vehicle theft using a tow truck can be detected by monitoring changes in the slope of the vehicle.

Although the degree of inclination of the vehicle itself can be easily detected by a slope detection means such as an acceleration (G) sensor, a change in the degree of inclination must be detected based on the degree of inclination at the start of parking.

The direct current slope change detection means stores the initial slope at the start of parking and compares this with subsequent slopes to find the change in slope at each point, so a memory is required to store the initial slope. become.

On the other hand, the alternating current slope change detection means calculates the slope change by differentiating the output of the slope detection means, and therefore does not require the above-mentioned memory. The present invention relates to a vehicle theft alarm system equipped with such an AC tilt change detection means.

[Conventional technology]

2. Description of the Related Art Conventionally, there is a device configured as shown in FIG. 17 for detecting changes in the degree of inclination of a vehicle in an alternating current manner.

In the figure, 11 is an acceleration sensor installed on the vehicle;
12 is a constant current circuit, and 13 is a differential amplifier, which constitute the slope detection means IO. 20 is this inclination detection means IO
31 is an AC amplifier that amplifies the output.

There are various types of acceleration sensor 11. In FIG. 18, a permanent magnet 72 is fixed to the tip of a swingable support rod 71, and displacement of the magnet 72 due to acceleration G is detected by magnetic detection elements (ball elements or magnetoresistive elements) 73 and 74 with opposite polarities. It is something. In this method, two magnetic detection elements 73.
The two outputs of 74 are input to a differential amplifier circuit and the difference is taken to cancel out variations in the elements.

On the other hand, FIG. 19 shows a structure in which diffused resistors Ra-Rd are formed in four directions on an elastically deformable semiconductor substrate 81 to form a bridge, one end of the substrate 81 is fixed, and a weight 82 is attached to the other end. This sensor utilizes the fact that when stress is applied to the substrate 81 due to acceleration G, the resistance Ra-RdO value changes due to the piezo effect, and the resistance value change is caused by the two output terminals A, It can be detected as the voltage generated between B.

Although the apparatus shown in FIG. 17 uses the acceleration sensor shown in FIG. 19, the sensor shown in FIG. 18 can also be represented by the same equivalent circuit. 13 in FIG. 17 is a differential amplifier that amplifies the minute output of the acceleration sensor 11, and includes a two-stage operational amplifier At,
A2 is used.

Reference numeral 20 denotes a slope change detection means that extracts only the alternating current bone (change in slope) from the output of the slope detection means 10. In principle, only a coupling capacitor is required, but in this case, a bypass consisting of a capacitor C and a resistor R is used. A filter (HPF) is used. 31 is A that amplifies the output of this HPF 20.
It is a C amplifier and is configured using an operational amplifier A3.

When the constant current (■) is 5 mA, the sensitivity of the acceleration sensor 11 is approximately 1.35 mV/0.5 G. G is the acceleration of gravity, and 0.5G corresponds to a tilt of 30°.

The resolution required for vehicle theft detection is minute at about 0.0523G at a detection angle of 3° acceleration, so if the threshold of the subsequent circuit is set to 0.5V, the total gain of the amplifiers 13 and 31 is 0.5V. Approximately 5G will be required. Furthermore, in order to detect a gradual jack-up over time, for example, if the tilt angle is 3° over 30 seconds, the cutoff frequency of the HPF20 is 0.0016f (
z, and the time constants of C and H become extremely large.

[Problem to be solved by the invention]

As mentioned above, when the time constants of C and H are large, when the vehicle is parked on a slope, the amplifying section 31 generates an output due to the residual charge in the capacitor C for a while from the time the vehicle starts parking, so it is difficult for the vehicle to be stolen during this time. When we meet, there remains an undetectable problem. For example, C=100μF.

When R is set to 1 MΩ, it takes more than 10 minutes to return to a steady value.

The present invention attempts to improve this point.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention, where IO is an inclination detecting means for detecting the inclination of the vehicle, and 20 is a device that extracts only the alternating current component from the output of the inclination detecting means 10 to detect changes in the inclination of the vehicle. Inclination change detection means 30 is an alarm means 40 that issues a theft alarm when the output of the inclination change detection means 20 exceeds a certain value.
is initialization means for resetting the output of the slope change detection means 20 to the parking start time of the vehicle.

The inclination detection means 10 includes an acceleration sensor 11 as shown in FIG.
, a constant current circuit 12, and a differential amplifier 13. Further, the slope change detection means 20 may also be an HPF whose cutoff frequency is set to 0.01 Hz or less, as in FIG. 17. The alarm means 30 is the AC amplifier 3 explained in FIG.
1 is provided with a comparator 32 having a threshold value for discriminating a slope change of, for example, 3 degrees or more, and an alarm device 33 that issues an audible or light alarm based on the discrimination output. Initialization means 4
0 resets the output of the slope change detection means 20 by a switch that is temporarily turned on at the start of parking. Specifically, the switch forcibly discharges the residual charge in the capacitor C of the HPF.

[Effect]

When a vehicle is parked on a slope, a change in the slope of the vehicle is detected at the start of parking, and the output of the slope change detection means 20 increases rapidly. FIG. 2 shows this at the output of the amplifier 31.

Although this output eventually decreases to a steady value, the change is gradual. This is because the time constants of C and H are set large in order to detect theft that tilts the vehicle by gently jacking up the vehicle.

In such a vehicle theft alarm system, when the residual charge of the capacitor C is forcibly discharged by the initialization means 40 at the start of parking, the output of the amplifier 31 immediately returns to a steady value, so even if the vehicle is parked on a slope, it is not possible to start parking. Theft monitoring becomes possible immediately after.

〔Example〕

FIG. 3 is a circuit diagram of the first embodiment of the present invention, in which the differential amplifier 1
3 to comparator 32 are shown in particular detail.

The differential amplifier 13 consists of an operational amplifier A1 that receives one output A of the acceleration sensor 11 as an input, and an operational amplifier A2 that receives the other output B as an input.By using the output of the operational amplifier A1 as the other input of the operational amplifier A2, Acceleration sensor 11
outputs an output according to the difference between outputs A and B. The DC reference voltage of the first stage operational amplifier AI is E2, which is the HPF
20, also used for biasing the AC amplifier 31.

The HP F 20 consists of a capacitor C and a resistor R, and an analog SW (initialization means) 40 is connected in parallel with the resistor R. The AC amplifier 31 is configured using an operational amplifier A3, and the subsequent comparator 32 is configured using two operational amplifiers A4. A5
is configured in window comparator format using . In other words, two types of reference voltages El and E3 have a relationship of E3>El, and E3 is connected to the non-inverting terminal of the operational amplifier A4.
Further, E2 is applied to the inverting terminal of the other operational amplifier A5, and the output of the operational amplifier A3 is commonly input to each of these inverse input terminals. Then, if a wired OR is configured with the output of the operational amplifier 7''A4.A5, if the output of the operational amplifier A3 is between El and E3, the output of the comparator 32 will be Hl.
Otherwise it will be L. Therefore, the alarm 33 is connected to the comparator 32.
When the output becomes L, an alarm will be issued. Two operational amplifiers A
4. The reason why A5 is used is to detect changes in the inclination of the vehicle, for example, in positive and negative directions in the X direction.

FIG. 4 shows a specific example of the initialization means 40.

In this example, FET 41 is connected in parallel with resistor R of HP F 20 and driven by npn transistor 42. When the reset signal becomes L, this transistor 42 turns off and turns on the FET 41. The reset signal is of a nature that remains low for a certain period of time from the start of parking, and is synchronized with the existing system monitor signal. FIG. 5 is an explanatory diagram of this.

This system monitor signal is created by the microcomputer 43, and enters the alert state after the chattering removal filter time has elapsed after the driver's side door key lock signal becomes L (lock completed, that is, parking starts). Before that, there is a waiting time of L level for a certain period of time. The reset signal is output after the waiting time.

The waiting time of the system monitor signal is intended to exclude the possibility that the driver may return to the vehicle again during the approximately 30 seconds that the driver is near the vehicle. Therefore, resetting within this time is not a problem at all due to the nature of the system; rather, the natural return to a steady value, which conventionally took several tens of minutes, is forcibly returned to a steady value within about 30 seconds after parking is started. The benefits are great.

By the way, when the vehicle is parked on a bridge or when a trunk or the like passes by the side while the vehicle is parked, the vehicle vibrates vertically and horizontally as shown in Figure 6(a)(t)), and the acceleration sensor detects this. Resulting in. If such external vibrations are received, there is a possibility that a false theft alarm will be issued, but this type of external vibrations has frequency characteristics and is generally in a band of 1 to 2H2. Therefore, in the present invention, as shown in FIG. 7, a low-pass filter (LPF) 50 with a cutoff frequency set to about IHz is used,
Either insert this between the initialization means 40 and the alarm means 30 as shown in (a), or insert it between the inclination detection means 10 and H as shown in (b).
Insert between it and PF20.

FIG. 8 is a circuit diagram of a second embodiment of the present invention embodying FIG. 7(a), in which the LPF 50 is composed of a parallel circuit of a capacitor C1 and a resistor R1 connected to the feedback path of an operational amplifier A3. This example has a simple configuration in which a capacitor C1 is added to the circuit shown in FIG. 3 (R1 is the original feedback resistance of the operational amplifier A3). In this way, if the cutoff frequency of HPF20 is 0.0IHz, it will be 0.01-1.0
A slope change in Hz becomes a target for a theft alarm.

FIG. 9 is a circuit diagram of a third embodiment of the present invention, which embodies the circuit shown in FIG. 7(b) using an active filter. LPF5 in this example
0 is an active filter composed of resistors R2 to R4, capacitors C2 and C3, and an operational amplifier A6, and is inserted after the differential amplifier 13. A7 is an operational amplifier that stabilizes the reference voltage E2, and is used in the AC amplifier 31 by adjusting it with a variable resistor VR2. Since the active filter can reduce the capacitance of capacitors C2 and C3, it is suitable for miniaturization.

Since the above-mentioned theft alarm device is operated while the vehicle is parked (with the engine stopped), it is desirable that the current consumption be as low as possible. Therefore, in the present invention, as shown in FIG. 10, an intermittent drive switch 61 is interposed between the constant current circuit 12 and the acceleration sensor 11, so that the current (2) is caused to flow intermittently. In this way, power can be saved depending on the on-ratio of the switch 61. For example, even if I = 5 mA is required, the average current consumption can be reduced to 115 mA by intermittently driving the switch 61 such that it is on for 1 second and off for 4 seconds.

However, when the switch 61 is turned on/off, the change affects the subsequent circuit through the capacitor C.

Therefore, a switch 62 is provided before the capacitor C and is operated in synchronization with the switch 61.

FIG. 11 is an operational waveform diagram in this case. Differential amplifier 1
This shows an example in which the output of 3 changes during the OFF period of 5W61.62 and then maintains a constant value. The solid line is the waveform during intermittent driving, and the broken line is the waveform during continuous driving shown for reference. The output of the AC amplifier 31 is slowly attenuated with time constants C and H. If the subsequent comparator determines that the first output of the AC amplifier 31 is greater than the threshold value, an alarm is issued and the state is locked.

FIG. 12 shows a fourth embodiment of the present invention, which embodies the structure shown in FIG. 10, in which a switch 6162 is added to the configuration shown in FIG. The switches 61 and 62 are driven by two types of intermittent drive signals (clocks) CKI and CK2. These clocks CKI and CK2 are synchronized, but the clock CK
The rising edge of clock CKI is slightly delayed with respect to clock CKI (described later).

FIG. 13 is an operation waveform diagram when a gentle slope change occurs. The output of the differential amplifier 13 indicates the magnitude of the slope, whereas the output of the AC amplifier 31 indicates the magnitude of the slope change. Therefore, when the slope increases as shown, the output of AC amplifier 31 also increases. Eventually, the slope stops changing (when the output of the AC amplifier 31 starts to attenuate as shown in FIG. 11), the output of the AC amplifier 31 corresponds to the charge of the capacitor C in the previous stage.

When the switch 61 is turned on, the output of the differential amplifier 13 rises with a constant time constant as shown in FIG.

Generally, it is stable at about 20 m5, so the rise of the switch 62 is delayed by about 20 to 30 m5 to apply a stable voltage to the capacitor C.

Although the above embodiments all show examples of detecting inclinations in one direction, in reality it is necessary to detect inclinations in two orthogonal directions.

FIG. 15 is a circuit diagram of a fifth embodiment of the present invention in which the above-mentioned respective sides are comprehensively incorporated to improve practicality.

In this example, one G sensor (acceleration sensor) 11 is used to detect inclination in the X direction, and the other G sensor 11' is used to detect inclination in the X direction. The constant current circuit 12 is shared by the two G sensors 11 and 11', and the differential amplifiers 13 and 13' are provided individually. A 1 ′ and A 2 ′ are operational amplifiers forming a differential amplifier 13′ in the X direction. The switches for intermittent drive are 61°62 for the X direction and 61' for the X direction.
, 62' are provided, the switches 61 and 62 are driven by the aforementioned clocks CKI and CK2, and the switches 61' and 62' are driven by the clocks CKI and CK2 described above.
are driven by opposite-phase clocks CKI and CK2 that are turned on during part of the off time of clocks CK1 and CK2. In this way, the configuration after the resistor R of the HPF 20 can be shared.

C' is a capacitor for detecting a change in inclination in the X direction.

The initialization means 40 is illustrated as an FET that is turned on by a reset pulse from the microcomputer 43. AC amplifier 31 is L
PF50 is connected to the return path.

The output of the comparator 32 is ORed by a diode Di, and output from the driver transistor Tr as a slope signal to the outside. The operational amplifier A7 is used to stabilize the reference voltage E2, but in this example, the operational amplifier A7 is also used to stabilize the reference voltage E1.
8 is used.

As shown in FIG. 16, the microcomputer 43 determines the parking start time from the states of the key rotor SW and lock SW, and first outputs a reset pulse to turn on the initialization means 40. This is the waiting time at the beginning of the system monitor signal (30 seconds)
Take advantage of. Then the system monitor signal is set to 0.5 Hz.
While flipping the system monitor indicator LED
91, and clocks CKI, CK2 . C.K.
Outputs I and CK2. These clocks have an on-time of 1
seconds, the off time is 5 seconds. However, clock CK2
．． CK2 has a rising edge of 30 m from clock CKI, CKI.
It's 5ec behind. During the reset period, these clocks are turned on for 15 seconds at a time to train the G sensor, etc.

The waveform in FIG. 16 shows that the slope in the X direction changes gradually and is detected by the G sensor 11'.

The output of the AC amplifier 31 cannot distinguish between the X direction and the X direction, but in any case, if there is a slope change exceeding the threshold value of the comparator 32, a slope signal is output. Microcomputer 4
3 turns on the relay 92 to sound the security horn 33 upon receiving this inclination signal, and continues to issue the theft alarm.

〔Effect of the invention〕

As described above, according to the present invention, a vehicle theft alarm system using an AC tilt change detection means has the advantage of being able to reliably detect theft immediately after the start of parking. It also has the advantage that it does not malfunction due to external vibrations and can prevent the battery from running out due to intermittent drive.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of the present invention, Fig. 2 is an operation waveform diagram of Fig. 1, Fig. 3 is a circuit diagram of the first embodiment of the invention, and Fig. 4 is a specific circuit diagram of the initialization means. , FIG. 5 is a signal waveform diagram of FIG. 4, FIG. 6 is a waveform diagram of external vibration, FIG. 7 is another configuration diagram of the present invention, and FIG. 8 is a circuit diagram of a second embodiment of the present invention. FIG. 9 is a circuit diagram of the third embodiment of the present invention, FIG. 10 is a different configuration diagram of the present invention, FIG. 11 is an operating waveform diagram of FIG. 10, and FIG. 12 is a circuit diagram of the fourth embodiment of the present invention. 13 is an operating waveform diagram of FIG. 12, FIG. 14 is a partially enlarged view of FIG. 13, FIG. 15 is a circuit diagram of the fifth embodiment of the present invention, and FIG. 16 is a diagram of FIG. 15. FIG. 17 is a block diagram showing an example of a conventional tilt change detection device; FIG. 18 is a block diagram showing an example of an acceleration sensor; FIG. 19 is a block diagram showing another example of an acceleration sensor. . In the figure, 10 is an inclination detection means, 11 is an acceleration sensor, and 12
13 is a constant current source, 13 is a differential amplifier, 20 is a slope change detection means, 30 is an alarm means, 31 is an AC amplifier, 32 is a comparator, 33 is an alarm, 40 is an initialization means, 50 is a low-pass filter, 60 is a switching means, and 61 and 62 are switches. Applicant Fujitsu Ten Ltd. Representative Patent Attorney Minoru Aoyagi Door 1? -Lock signal jlls Fig. 12 and "-m- 1i, tLY-, L-work, I3. Figure AC amplifier 31 output + + - - One slope change (a) Structure diagram fb1 Equivalent circuit diagram Figure 19

Claims (1)

[Claims] 1. An inclination detection means (10) mounted on a vehicle to detect the inclination of the vehicle; and an inclination change that detects the change in the inclination of the vehicle in an alternating current manner from the output of the inclination detection means (10). a detection means (20); an alarm means (30) for issuing an alarm when the output of the slope change detection means (20) exceeds a certain value; and a residual output of the slope change detection means (20) when the vehicle starts parking. A vehicle theft alarm device comprising: initialization means (40) for forcibly resetting. 2. The vehicle theft according to claim 1, further comprising a low-pass filter (50) that provides the alarm means (30) with only low frequency components from which external vibrations have been removed from the output of the slope change detection means (20). Alarm device. 3. Inclination detection means (10) and inclination change detection means (20)
2. The vehicle theft alarm system according to claim 1, further comprising switching means (60) for synchronizing and intermittent operation of the vehicle theft alarm system.