JPS6318799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a support structure for a detection line in an electric field type human body detection device.

Figure 1 shows an example of a conventional electric field type human body detection device, in which 1 is an oscillator, 2 is an excitation line,
3 is a detection line, 4 is an amplifier connected to the detection line, 5 is a detection circuit, 6 is a bandpass filter, 7
is a comparator, 8 is a switching circuit, and 9 is a terminating resistor. The electric field type detection device attempts to detect an intruder by changing the capacitance between the excitation line 2 and the detection line 3. That is, when a human body crosses the detection line, a capacitance change occurs between the human body and the detection line, which causes an induced voltage change. This change is detected through a detection circuit, passes through a bandpass filter, and enters a comparator that detects the level of change. When this level is higher than a set value, a switching output is generated.

Consider a case where the detection wire of such an electric field type human body detector gets wet with water.

If the conventional detection wire 2 and support part 10 leak into water, the wet portion 11 becomes an electrode as shown in FIG. 2, and a coupling capacitance C _w is generated between the detection wire and the detection wire. Also, this wet part generates a coupling capacitance C _pw with the ground, so in the end, the capacitance of the sensing wire is △C _w = C _w・C _pw / C _w + C _pw (1) This will increase.

Therefore, by detecting the increase in capacitance △C _w due to this water leakage, the electric field detector can:
This will result in false alarms.

If the surface of the detection wire is a conductor, an electrode is formed by wetting the supporting portion, which is an insulator, as shown in FIG.

If the electrode formed by this water droplet is insulated from the sensing wire, a capacitance change as shown in equation (1) will occur, but if it is electrically connected to the sensing wire, the sensing wire will change. The electrode area increases, and the capacitance of the detection line increases.

The present invention has been proposed to improve the above-mentioned drawbacks. Figures 4A and 4B show an embodiment of the present invention. In the figure, 21 is a detection wire, 22 is a cover that supports the detection wire, and has a conical shape whose inner diameter increases toward the bottom, and a support 2 made of an insulator.
3 is connected to the cover at the inner upper part of the cover. Further, the surfaces of the detection wire 21 and the cover 22 are formed of a conductor. By having such a configuration,
Even if the detection wire 21 and the cover 22 get wet due to rain, new electrodes will not be formed, and the presence of the cover can prevent the support itself from getting wet with the rain. The capacitance change △C _w of the detection line caused by leakage into water is much smaller than in the past. The structure of the cover must be such that it has a water-tight top to prevent water from accumulating, and the tangential direction of the bottom of the cover must face outward.

The structure shown in FIG. 5 is disadvantageous because rainwater flows into the support, increasing the electrode area.

6 to 11 show other embodiments of the present invention, in which FIGS. 6 and 7 have a bell-shaped cover, and FIG. 8 shows that water falling down the cover is supported. In order to prevent water from getting on the rod and forming a new electrode, a gutter 24 is provided at the bottom of the cover to allow water to fall from a position far away from the support rod.

In FIG. 9, a rain return plate 25, that is, a plate-like member is provided inside the cover perpendicularly to the support, thereby preventing water from entering the inside of the cover even when rain blows up from below.

In FIG. 10, a constriction 26 is formed in the middle of the cover, and the constriction makes it difficult for water to enter the inside of the cover. Moreover, this constriction can increase the creepage distance inside the cover, so that it takes time for the inside to get wet when condensation occurs.

In FIG. 11, an outwardly expanding portion 27 is provided at the bottom of the cover to easily deflect rain.

In electric field type human body detection devices, the causes of malfunction due to water droplets such as rain can be broadly divided into (a) changes in the area of the detection electrode (detection wire) itself; (The worst case scenario is a short circuit) (b) There are two possible causes: a change in the area of the counter electrode (earth electrode or space electrode) where the sensing electrode forms a capacitance.

(a) As shown in FIG. 3, when the water droplet 11 in contact with the detection line 2 flows down the support (insulator) 10, a large capacitance change occurs. The reason for this is that when water droplets flow through the support, they form a band-like flow, which in the worst case can result in a short circuit with the ground electrode. That is, in a state where a short circuit does not occur, the distance to the ground electrode becomes very close, causing a large capacitance change.

In either case, the problem is that water droplets in contact with the detection wire move (fall) on the insulator while forming new electrodes.

(b) Even if the water droplet is not in direct contact with the detection line, the same phenomenon as in (a) will occur as the electrode formed by the water droplet is closer to and larger than the detection line.

Based on the above considerations, the present invention is a supporting section invented. Its characteristics are as shown in FIG. 4: (a) Since the cover 22 is a conductor, there is no formation of new electrodes due to adhesion of water droplets.

(b) Since the shape of the cover 22 expands downward, when water droplets fall, they are released into the space without contacting the insulator of the support 23.
A large capacitance change does not occur, and of course a short circuit cannot occur.

(c) Since the support portion (insulator) 23 is surrounded by the cover 22, water droplets will not adhere to the portion close to the detection line, that is, the connection portion. Also,
In the vicinity of the support where the cover becomes ineffective, even if water droplets adhere, the cover is spread out and the distance is long, so the coupling capacity is small.

Due to the above three major features, the present invention has a greater effect on malfunctions caused by water droplets than the conventional case where the device is simply supported by an insulator.

Next, experimental comparison data are shown in FIGS. 12 and 13.

Fig. 12 shows the conventional device, and Fig. 13 shows the device of the present invention, where the horizontal axis shows time and the vertical axis shows time.
The BPF output, that is, the output of the bandpass filter (bandpass filter 6 in FIG. 1) is shown.
This was to detect changes in the capacitance of the detection circuit, and the rainfall was approximately 30mm/min. As a result, in the conventional device, the output changes drastically (see FIG. 12), but in the present invention, the output changes less as shown in FIG. 13, and the superiority of the present invention is recognized.

Since the present invention is configured as described above, (a) the capacitance of the sensing wire does not change even if the sensing wire and the sensing wire/support part become wet with water; and (b) weather conditions. As a result, dew condensation may occur on the detection wire/support part, but even in such a case, with the configuration shown in Figure 10, the capacitance of the detection wire will change very slowly. No false alarms will occur. That is, the electric field type human body detector has the effect of detecting changes in capacitance, but not detecting changes in capacitance that are very gradual.

[Brief explanation of the drawing]

Figures 1 to 3 are explanatory diagrams of conventional examples, Figure 4 A,
B is an embodiment of the present invention, FIG. 5 is an explanatory diagram, and FIGS.
FIG. 11 shows another embodiment of the present invention; FIG. 12 shows the conventional device, and FIG. 13 shows the change in capacitance of the detection line with respect to rainfall in the device of the present invention. 21...Detection wire, 22...Cover, 23...Support, 24...Gutter, 25...Rain return plate, 26...
Waist part.

Claims (1)

[Scope of Claims] 1. A detection line formed of a conductor, a cover coupled to the detection line, formed of a conductor, and sloping downward and outward, and coupled to the inside of the cover. A detection wire support device for an electric field type human body detection device, which is composed of an insulator support. 2. The detection wire support device according to claim 1, wherein the cover has a conical shape. 3. The detection line support device according to claim 1, wherein the cover is in the shape of a bell. 4. The detection line support device according to claim 1, wherein a gutter is provided at the bottom of the cover. 5. The detection line support device according to claim 1, wherein a rain return plate perpendicular to the support body is provided inside the cover. 6. The detection line support device according to claim 1, wherein the cover has a constricted portion in the middle.