JP2889993B2 - Vehicle anti-theft device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] In a vehicle anti-theft device that detects a change in inclination of a vehicle and issues an alarm, an object of the invention is to reduce the influence of offset due to temperature drift of an inclination angle sensor and an amplification element. The initial value for calculating the change in inclination is updated every predetermined time.

[Industrial applications]

The present invention relates to a vehicle antitheft device that detects a change in the inclination of a vehicle and issues an alarm.

[Conventional technology]

When the inclination angle sensor mounted on the vehicle detects the inclination angle of the vehicle, the processor that processes the output of the sensor calculates the inclination change during parking, and when the inclination change exceeds a predetermined threshold value. Has a vehicle anti-theft device that issues an alarm. This device is useful for preventing the act of jacking up a vehicle and stealing the vehicle body or wheels.

The direct current vehicle antitheft device stores the sensor output at the start of parking as an initial value, and issues an alarm when a difference from the subsequent sensor output (corresponding to a change in inclination) exceeds a predetermined threshold value.

[Problems to be solved by the invention]

If the above-described vehicle anti-theft device is affected by a large outdoor temperature change, the offset of the tilt angle sensor and the input offset of the DC amplifier receiving the output of the sensor are DC-amplified and a large error occurs, causing a malfunction. (A false alarm is issued).

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the influence of an offset due to a temperature drift of a tilt angle sensor and an amplifying element in a vehicle antitheft device.

[Means for solving the problem]

According to the present invention, a tilt angle sensor mounted on a vehicle detects a tilt angle of the vehicle, a processor that processes an output of the sensor calculates a tilt change during parking, and the tilt change is determined by a predetermined threshold value. In the vehicular anti-theft device that issues an alarm when exceeding, a plurality of determination systems for comparing the inclination change with a predetermined threshold are set, and each determination system sets an initial value for calculating the inclination change every predetermined time. In addition to the updating, the initial value updating timing is different from each other.

[Action]

If the initial value for calculating the change in inclination is updated every predetermined time, the change due to the temperature drift of the offset will not be accumulated for a long time, and a warning will be issued even though the inclination angle of the vehicle has not actually changed. Malfunction can be prevented beforehand.

Further, when a plurality of determination systems are provided and the initial value update timings are made different from each other, an output change that cannot be detected by one determination system is detected by another determination system, and the tilt angle change can be more reliably detected.

〔Example〕

FIG. 1 is a schematic configuration diagram of the present invention, wherein 10 is an inclination angle sensor for detecting the inclination angle of a vehicle from a gravitational acceleration or the like, 20 is an amplifier for DC amplifying a minute output of the sensor, and 30 is vibration or the like from the output of the amplifier. A filter for removing a noise component caused by the A / D converter for converting the output of the filter into a digital signal;
Is a processor (using a microcomputer) which takes in the output of the A / D converter and detects inclination change.

Figure 2 is an operation explanatory diagram of the present invention, V _N is the inclination angle sensor 10
Is the output of The sensor output V _N denotes the inclination angle of the vehicle. The inclination change is calculated as the difference between the inclination angle at a certain point in time (this is called an initial value) and the current inclination angle. Generally initial value is a value of the sensor output V _N at the time of system start,
In the example of the figure, V _A1 corresponds to this. In the present invention, this initial value (general term is _VA ) is set to a fixed time (60 s in the example in the figure).
Update every time. The value of V _N 60 seconds after the start is V _A2 , and the value of V _N 60 seconds later is V _A3 , so the initial value V _A is updated to V _A1 , V _A2 , V _A3 , ... It has been trying to follow the change of the sensor output V _N.

The change of the sensor output V _N, there is a due to the offset changes due to the inclination change and the temperature drift of the vehicle. The former changes greatly in about 30s due to jack-up, while the latter is extremely slow, so for example
By updating the initial value every 60 seconds, it is possible to detect a change in the vehicle's inclination that leads to theft while avoiding the effects of temperature drift.

For example, the solid line in the example of FIG.
The broken line is due to jack-up. And if the threshold value to alert was V _R, the maximum value of the output change due to temperature drift (V _A2 -V _A1), set so as not to have (V _A3 -V _A2), ...... in alarm deep. Such output change by the jack-up even if the there is a (V _N1 -V _A1), this is an alarm comes out if it exceeds the threshold value V _R.

In the way one system initial value updating method, output change immediately before updating the initial value V _A, for example, (V _N1 -V _A1) is less than V _R, updating the initial value from the V _A1 to V _N1 Causes the output change to become zero, so the output change (V _N1
-V _A1) close to is V _R, it may not be possible to detect this even exceed V _R if some time.

In order to solve this problem, a plurality of determination systems having different initial value update times may be introduced. V _B and V _{C in} FIG. 2 are initial values of other judgment systems, and V _B is V _B1 , V _B2 and V _B3 20 s later than _VA.
, And V _C is updated like V _C1 , V _C2 20 s later than V _B. When a plurality of determination systems are introduced in this manner, a large output change that cannot be detected by one determination system can be detected by another determination system. For example, an output change that cannot be detected at V _A (V _N1 −V _A1 ) <V _R by V _B after 20 s (V _N2 −V _B1 )> V
Can be detected as _R.

The initial value of each judgment system is updated every 60 seconds, but the threshold V _R
Not all systems need to be performed at all times, and each system has 20
It suffices to go in order by shifting by s. That is, V _A → V _B → V _C
→ V _A → V _B → However, from the start when V _B and V _C are not stored, until 40 s, judgment is made only with V _A.

FIG. 3 is a flowchart showing the processing in this case. Here, the timing counter T and two types of flags
F _B, using F _C, also the initial value V _A, V _B, is V _C is shown as a memory for storing the sensor output V _N at the time of update.

First write V _N at the start to V _A at the initialization process of step S1, also with sets 2 to T, F _B, F
Clear _C to 0. Next, in step S2, the interval time of this routine is set to 20 s. And F in step S3
Check the value of _C. Since This F _C initially V _N is written into the V _C (40 s from the start) is 0, during which executes step S4. This step S4 is for detecting the tilt changes in the initial value V _A, where | alert in step S5 if _{a> V R | V N -V A} . However, after passing through both steps S3 and S4 at N (No), T is decremented (DEC) at step S6. Since the initial value of T is 2, the first time through step S6, T = 1. Therefore, if it is determined in step S6 that T = 2, the result is N, so that step S8
Move to Here, if it is determined that T = 1, the determination is Y (yes), and the process proceeds to step S9. In this step S9, it is determined whether F _B = 0. Since the start and is F _B = 0 If only not elapsed 20s return writes V _B = V _N at step S10, after setting to 1 F _B at the next step S11 to step S2.

When the next 20 s (40 s from the start) elapses in this step S2, the process moves from step S3 through step S4 to S6, and T
Is further decremented to zero. This results in a step
The process moves to step S12 via S7 and S8, sets T to 3, and then goes to step S13. Check F _C here. Initially, since F _C = 0, V _N is written to V _C in step S14, and F _C is written in step S15.
Is set to 1 and the process returns to step S2.

Further, when the next 20 s (60 s from the start) elapses in step S2, the flow directly goes to step S6 from step S3, where T = 2 is decremented. As a result, the process moves from step S7 to step S16, and the output change is determined based on _VA . If the result that less than V _R In this determination to update the V _A at step S17, the flow returns to step S2.

Furthermore, when this next 20s in step S2 (80s from the start) has passed, since decrementing T = 1 in step S6, it enters the step S9, wherein the output change judgment by V _B in step S18 to be judged as N Is performed. V _B in step S10 if the determination result that less than V _R in
And returns to step S2.

When the next 20 s (100 s from the start) elapses in step S2, the value is decremented to T = 0 in step S6. Therefore, the process proceeds to step S12, and further proceeds to step S13.
To enter the S19, the output change judgment by V _C are performed. If the result of this determination is smaller than V _R , in step S14 V _C
And returns to step S2.

In the same manner, judgment and update by V _A every 20 s, V _B
Determining and updating by, a determination and update by V _C, step S16, S18, alert in step S5 When the results of greater than V _R is obtained in any of S19.

〔The invention's effect〕

As described above, according to the present invention, in a vehicle anti-theft device that detects a change in the inclination of a vehicle and issues an alarm, it is possible to reduce the influence of offset due to temperature drift of the inclination angle sensor and the amplification element.

Further, there is obtained an advantage that an output change that cannot be detected by one determination system is detected by another determination system, so that it is possible to more reliably detect a change in the inclination angle.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is an explanatory diagram of the operation of the present invention, and FIG. 3 is a flowchart showing the processing of the present invention. In the figure, 10 is an inclination angle sensor, 20 is a DC amplifier, and 50 is a processor.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60R 25/10

Claims (1)

(57) [Claims] An inclination sensor mounted on a vehicle detects an inclination angle of the vehicle, and a processor for processing the output of the sensor calculates a change in inclination during parking, and the inclination change is a predetermined threshold. In the vehicle anti-theft device that issues an alarm when the value exceeds the threshold value, a plurality of determination systems for comparing the inclination change with a predetermined threshold value are set, and each determination system sets an initial value for calculating the inclination change at predetermined time intervals. A vehicle anti-theft device characterized in that the initial values are updated at different times.