JPS61247911A - Inclination sensor for automobile - Google Patents

Abstract

PURPOSE:To prevent a theft of an automobile tire by detecting an inclination of the automobile with good accuracy. CONSTITUTION:When an iron core 3 is fixed on an automobile body, the iron core 3 is inclined in a body with the automobile body. With reference to this, since a movable iron core 1 holds an angle in a pendulum state so as to face in a direction G of the gravity at all times, an angle theta of inclination is generated between both. At this time, when the facing part of the iron cores 1 and 3 is made in a comb shape, the resolution with reference to the angle theta of inclination is improved. Consequently, when the titled inclination sensor is utilized, a system to sound an alarm automatically can be constituted by jacking up and inclining a part of the car body at the time of the theft of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a simple tilt sensor for automobiles that utilizes a magnetic circuit.

[Conventional technology]

There are ways to prevent car tires from being stolen, such as locking the tire fastening bolts, but generally speaking, if you focus on jacking up the car body and removing the tires, you can detect whether the car body is tilted and generate an alarm. Emitting a message is also a measure to prevent theft.

[Problem that the invention seeks to solve]

However, if a tilt sensor of this type is used for high-precision measurement, such as those used in the field of construction machinery, there is a drawback that it increases costs. The present invention attempts to detect the inclination of a vehicle body simply and with relatively high accuracy using a magnetic circuit.

[Configuration and action]

FIG. 1 is a diagram showing the principle of the present invention, in which 1 is a movable iron core, 2 is a rotating shaft set above its center of gravity, 3 is a fixed iron core, and 4 is a coil. The movable iron core 1 and the fixed iron core 3 constitute a closed magnetic path, but there is an air gap d between them. When the iron core 3 is fixed to the vehicle body, the iron core 3 tilts integrally with the vehicle body. On the other hand, since the movable iron core l always maintains its swing angle along the gravitational direction G, an inclination angle θ is generated between the two. At this time, the opposing portions of the iron core 1.3 are made into a comb shape (and the resolution with respect to the inclination angle θ is improved).

FIG. 2 is a characteristic diagram showing the relationship between the inclination angle θ and the inductance L of the coil 4, and the maximum value L max is shown in FIG. The minimum value Lmin is the state in which the teeth of one comb are located between the teeth of the other (maximum air gap).The magnetic flux at this time is expressed by φ1.φ2 as shown in the following equation. It becomes like this.

φ1=□ Rc+Mmax φ2=□ Rc+R+++in Here, Re is the magnetic resistance of the iron core 1.3, Rmax+Rl
1 inch is the maximum and minimum magnetic resistance of the air gap d, N
is the number of turns of the coil, and 1 is the current flowing through the coil 4 (N
-i is magnetomotive force).

Generally, the relative magnetic permeability of the iron core with respect to air is about 1000, so the relationship is Rmax':)>RoIin>>Rc. Therefore, Lmax and Lmin in FIG. 2 are as follows. Here, S is the cross-sectional area of iron core 1.3, d max
+d win is the maximum and minimum value of the air gap d.

When measuring the change in the inductance L mentioned above, the inclination angle θ
can detect changes in Therefore, by using this inclination sensor, it is possible to configure a system that automatically issues a warning when a part of the vehicle body is jacked up and tilted when a tire is stolen. This will be explained in detail below with reference to illustrated embodiments.

〔Example〕

FIG. 3 is a circuit diagram showing an embodiment of the present invention, in which the middle point 40 of the coil 4 is grounded. 5 is a control CPU (microcomputer), and its baud) PI and R2 give pulses of opposite phase to the driver transistor 6.7. When transistor 6 is turned on, resistor R is connected to the +12V power supply.
t, a current flows through one end 41 of the coil 4 via the diode D1 (this current flows to the midpoint 40). On the other hand, when the transistor 7 is turned on, the resistor R is connected to the +12V power supply.
2. A current is caused to flow through the other end 42 of the coil 4 via the diode D2 (this current also flows to the midpoint 40).

Therefore, the movable core 1 tries to rotate in opposite directions alternately, but if the pulse period of PI and R2 is short, it becomes a kind of AC electromagnet, and the movable core 1 changes its relative position with respect to the fixed core 3. become unable to do so. In this way,
It is possible to prevent the movable iron core 1 from rotating due to vibrations during traveling and the shaft 2 from being worn out.

However, the reason why pulses of opposite phase are generated from P+ and R2 is to prevent the movable iron core l from being magnetized in one direction by the residual magnetic field.

On the other hand, if pulses are generated from boats PI and P2 like this, inclination cannot be detected, so while the boats are stopped, boat) PI,
Both R2 are set to L (low) to turn off the transistor 6.7 and allow the iron core 1.3 to rotate relative to each other. Instead, a detection pulse A is generated from port P3. Since this pulse A is not for exciting the coil 4, the current value is made small. Specifically, resistor R3 is replaced by R1, R
2 (=120Ω) and do not use a driver. Also, there is no need to shorten the cycle (set it to the required search cycle). Then, this pulse A is passed through a resistor R3 and a diode D3 to one end 41 of the coil 4 (
or the other end 42).

In this way, the voltage B on the cathode side of the diode D3 is influenced by the inductance L of the coil 4, and its waveform becomes dull. For example, in the rising portion, the voltage rises as shown in FIG. 4 (VH is a steady value on the H (high) side). The time constant at this time is determined by the inductance L of the coil 4 and the resistance value R of the resistor R3, so when L changes, the rise time changes. Therefore, the comparator 8 sets the voltage B to a constant value v
By comparing with th, the time ti at which the output of the comparator 8 is inverted from H to L can be obtained. Pulse A in CPU5
The rise of t.

Since the delay time τ from time to time t1 can be calculated, it is possible to determine whether the vehicle body is tilted from this value.

FIG. 5 is an example of a flowchart showing this process.

For example, the decision to stop a car is made by turning on the ignition key,
Determine OFF. This is to distinguish between cases where the car stops temporarily while driving and cases where the car is parked. If it has not stopped, ports PI and P2 are controlled to turn transistor 6.7 on and off alternately, but if it has stopped, Pl,
Both P2 are set to L, and a detection pulse A is output from P3. Then, the rise of pulse A (time to)
Start the timer (soft counter) with
When the output of comparator 8) is inverted to L (time 1+
).

When P4 is inverted to L, τ is obtained from the relationship t+to=τ (if to=0, τ=tI), and this is temporarily stored in the RAM to determine whether there is an inclination.

One possible method for this is to compare the obtained τ with a fixed value set in advance, but this would lead to malfunctions if the car is parked on a slope.
It is desirable to use a reference value of τ as a reference value and compare subsequent τ values. If they match, nothing will be done, but if they do not match, an alarm will be issued. However, even in this case, it is preferable to set a predetermined margin Δτ and issue an alarm when the subsequent τ becomes equal to or greater than τ0+Δτ, or conversely when it becomes equal to or less than τ0−Δτ.

〔Effect of the invention〕

As described above, according to the present invention, inclination can be detected with relatively high accuracy with a simple structure, so there is an advantage that an alarm system for preventing automobile tire theft can be realized at a low cost.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a characteristic diagram thereof, FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIGS. 4 and 5 are operational waveform diagrams and flow charts thereof. In the figure, 1 is a movable core, 2 is its rotating shaft, 3 is a fixed core,
4 is a coil, 5 is a CPU, 6.7 is a transistor, and 8 is a comparator. Applicant Fujitsu Ten Ltd. Representative Patent Attorney Minoru Aoyagi (α) Front view (b) 11th page 3 Principle of the present invention Figure 1 However, 1 force 1! Ie Characteristic diagram of Figure 1 Figure 2 Q-Width C0GIII3L4d Fuo-Cheet Figure 5

Claims (1)

[Claims] A movable iron core that is rotatable about a horizontal axis, a fixed iron core that has a predetermined air gap between the iron core and the closed magnetic circuit, a coil wound around the fixed iron core, and the fixed iron core. 1. A tilt sensor for an automobile, comprising a circuit that detects the tilt of the vehicle body based on a change in the inductance of the coil in a state where the iron core is fixed to the vehicle body side.