JPH0226414B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to a proximity switch device for automatic doors, and more particularly to a proximity switch device for automatic doors with variable oscillation frequency and high sensitivity.

(Prior technology) High-frequency oscillation type proximity switches used in automatic doors of buildings, etc. have a sensing plate made of two conductive plates embedded in the mat part, and oscillate a high frequency of 1 to 20MHz in the oscillation part. The sensing plate is used as part of the oscillation circuit. When the human body approaches the mat, the frequency of the oscillation circuit changes due to stray capacitance and resistance loss between the human body and the sensing plate, and the output level changes as the sharpness Q changes. The change is taken out to the outside and operates the switch part,
This controls the opening and closing of the automatic door.

5A and 5B show the structure and embedding of a conventional sensing plate device, in which two sensing plates 30,
A resin frame 32 is sandwiched between 31, and a printed circuit board circuit (oscillation circuit) 33 having electronic elements such as transistors mounted thereon is disposed, and lead wires 34 and 35 from the printed circuit board 33 are connected to each other. It is connected to sensing plates 30 and 31 by soldering or the like. After making a predetermined adjustment, it is fixed with a mold 36 and is buried under the floor near the entrance of the automatic door. Power is supplied to the printed circuit board circuit 33 via a transmission line 37, and the detection signals detected by the sensing plates 30 and 31 are transmitted to a switch circuit separately arranged in the automatic door drive section, and this opening/closing signal is It is designed to control the opening and closing of the door.

Here, to explain the principle of such a sensing plate device, first, FIG. 6 shows an example in which sensing plates 30 and 31 are used as part of an oscillator without a feeder.
Part of the Hartley type LC oscillator is shown.
The oscillation condition for this oscillator is that since the feedback reactance is capacitive (C _d ), Z ₁ and Z ₂ are inductive reactances. The reactance curves of the inductive reactances Z ₁ and Z ₂ are shown in FIG. In FIG. 7, the solid line shows the characteristics on the base side of the transistor _Q1 , and the broken line shows the characteristics on the collector side of the transistor _Q1.As shown in _FIG. The dashed line shows the case where the resonant frequency shifts to f ₀₁ ' due to the vibration. Now, if the adjustment is made so that f ₀₁ <f ₀₂ as shown in FIG. 7, this condition is satisfied in the area shown by diagonal lines.
However, it is well known that the actual oscillation frequency is near the frequency f ₀₁ where the reactance is large.

Here, in FIG. 6, the tuning circuit provided on the base side of the transistor _Q1 is connected to the sensing plate 30.
and 31 capacitance as C _c , fixed capacitance C ₂ and coil L ₁ The tuning circuit on the collector side is the adjustment capacitor C ₃
and in coil L ₂ becomes. Then, according to equation (2), the oscillation output is adjusted to the maximum by adjusting the variable capacitor _C3 so as to meet the conditions shown in FIG. In such a state, when a hand or the like is brought close to the sensing plates 30 and 31 as shown in FIG _. There is a capacitance C _b between the sensing plates 30 and 31, and the capacitance C _c between the sensing plates 30 and 31 is (1/
(1/C _a +1/C _b )). Here, since the opposing area between the human body and the ground is large, the capacitance C _a satisfies C _b ≪ _{C a} and can be considered to be almost the sum of C _b . As a result, the sensing plate capacitance (C _c + C _b )
According to equation (1), the tuning frequency decreases by this amount, and the resonance frequencies f ₀₁ and f ₀₂ are detuned, so the oscillation output decreases. The automatic door is switched by detecting this change. This is the basic principle of automatic doors, and even if the oscillation circuit is changed, the operation shown in FIG. 8 will not change. In addition to the capacitance, a loss resistance R is also added, which acts to reduce the sharpness Q of the circuit, and in this case as well, the oscillation output is reduced and a large detection signal can be obtained.

Here, the size of this type of sensing plate used for automatic doors is quite large, 200 x 200 mm to 1000 x 1000 mm, and the transmitter is used as a capacitor to apply high frequency voltage to the sensing plate. In order to do this, the supply line could not be made longer unless a feeder was used, and the only way to do this was to install the transmitter inside or near the sensing plate. If the supply line is made too long, it will be emitted as radio waves and will not reach the sensing plate. Two parallel sensing plates have a structure that makes it difficult to emit radio waves as antennas, but when such sensing plates are buried underground at the exit of an automatic door as shown in Figure 5, sensing plates 2 If the antenna is not completely grounded, the supply line (signal line) will operate as part of the antenna, that is, as one half of a dipole antenna, and radio waves will be emitted as shown in FIG. Therefore, fluctuations occur in the oscillation output, resulting in malfunction. High-frequency current carried through the transmitter power supply and signal wires may reach the next room through the power line, causing sudden changes when plugging in or removing the plug from an outlet, etc., causing the proximity switch to continue to operate or not to operate. occurs.

Here, the fact that the sensing plates 30 and 31 as shown in FIG. It is described on page 70 of ``Antenna/Transmission Circuits.''
That is, as shown in FIG. 9A, the sensing plates 30 and 31 act as a type of capacitor if the supply line is ignored, but when one of the capacitors is opened, radio waves are emitted. Then, when the supply line as shown in FIG. 9B is arranged, since the sensing plate 31 and the supply line are at the same potential, a part of the high frequency current begins to radiate, and finally the state as shown in FIG. This results in a dipole antenna state as shown in Figure 10. If the sensing plate 31 is incompletely grounded, radio waves will be emitted between the sensing plate 30 and the supply line, and the maximum radiation will be reached when the length of the supply line reaches, for example, λ/4 of the wavelength λ. This may lead to malfunction.

By the way, since the oscillation part uses the sensing plate as part of the oscillation circuit, it is best to place the oscillation part near the sensing plate.
When buried underground, due to the impedance of the sensing plate, it is common to use it by placing it inside the sensing plate within the same electric field. However, when the oscillating section is separated from the sensing plate, another electric field is generated in the feeder line connecting the two due to impedance, making the sensing plate no longer usable as part of the oscillating circuit. That is, the 11th
The figure shows a Colpitts-type oscillation circuit 40 with a sensing plate 41,
The distance d between the two upper and lower sensing plates 41 and 42 is constant, so that even if the switch section is placed at an arbitrary location, there will be no significant difference in the oscillation conditions. It's getting old. Therefore, C _c is the stray capacitance between the sensing plates 41 and 42, and R _c is the stray capacitance between the sensing plates 41 and 42.
C ₂ and C ₃ are the divide capacitors. Also, C ₆ is a coil
This capacitor is used to adjust the oscillation frequency in synchronization with L ₁ , but due to the stray capacitance C _c , C _a = C ₆ + C ₂ (C _c + C ₃ )/C ₂ + C ₃ + C _c ……(3
), and the oscillation frequency is determined by this capacitance C _a , so the frequency cannot be changed much. For this reason, even if the device is operating normally before being buried, oscillation stops or the oscillation output decreases when buried, making it difficult to put it into practical use.

Furthermore, in a structure in which the oscillation part is housed within the sensing plate,
This is a big practical inconvenience. That is, in the case of inspection and repair due to a malfunction in the oscillation section, it is necessary to remove the entire sensing plate, and in particular, removing the floor such as tiles is a large-scale construction work. Further, although it is sufficient to provide a hole for maintenance in advance, providing such a hole on the floor in front of the door poses problems both from the viewpoint of appearance and from the viewpoint of smooth passage.

This invention was made in consideration of the above-mentioned problems, and is a proximity switch device for an automatic door in which the oscillation frequency of the sensing plate is uniquely set by a loading coil, making it less susceptible to surrounding influences. is intended to provide.

Structure of the Invention; (Means for Solving the Problems) The present invention relates to a proximity switch device for an automatic door, and the above object of the present invention is to provide two sensing plates and a high frequency oscillation circuit disposed between the sensing plates. and a loading coil that is inserted between one of the sensing plates and the input section of the high frequency oscillation circuit and has an inductance that resonates with the stray capacitance of the sensing plate, and detects the output level of the high frequency oscillation circuit. and a switch circuit connected to the high frequency oscillation circuit for controlling the opening and closing of the door, and a check coil inserted in a power line and a signal line, respectively, between the high frequency oscillation circuit and the switch circuit. It is achieved by doing so.

(Function) The necessary oscillation conditions for a high-frequency oscillation type proximity switch are not good conditions because if the oscillation is too stable, it will not change much even when a human body or the like approaches. Further, even if the oscillation is too unstable, the change can be made large, but the oscillation may stop when buried. Therefore, appropriate stability and instability elements are required. With the conventional type without loading coil (Fig. 11), the oscillation frequency is determined by the sensing plate stray capacitance C _c as shown in equation (3), so it is difficult to determine the above oscillation conditions. Difficult work was required. Therefore, in some cases, a problem occurred in that the oscillation stopped when the sensing plate was buried. However, by inserting a loading coil, the oscillation part can be adjusted regardless of the stray capacitance C _c of the sensing plate as shown in equation (5), so it is possible to create the optimal oscillation conditions, and it is possible to create a stable automatic door. A proximity switch device can be created.

In this invention, a loading coil is inserted between the sensing plate and the high frequency oscillation circuit, and the oscillation frequency of the sensing plate is uniquely set by the loading coil, so that it is hardly influenced by the surroundings. Moreover, the oscillation conditions can also be ideally adjusted.

(Embodiment) As shown in FIG.
and 3B, and these two sensing plates 3A and 3B are part of the oscillation element, and these sensing plates 3A,
3B, a loading coil _L2 and a resistor _R4 inserted between the sensing plate 3A and the input part of the high frequency oscillation circuit 4, and the output level of the high frequency oscillation circuit 4. A switch circuit 6 connected to a high frequency oscillation circuit 4 for detecting the door opening/closing control, and a power line l1, l2 and a signal line l3 connected between the high frequency oscillation circuit 4 and the switch circuit 6, respectively. Interposed chiyoke coil
L ₃ , L ₄ and L ₅ are provided.

As mentioned above, the sensing plate 3A originally functions as a capacitor, and since the loading coil L ₂ and the resistor R ₄ are inserted into the input section of the oscillation circuit 12, the oscillation frequency of the oscillation circuit 4 depends on the inductance. L ₄ and capacity Ca Ca = C ₆ + C ₂ · C ₃ / C ₂ + C ₃ ... (4) However, it is determined by C ₂ ≫ _{C 3} . On the sensing plates 3A and 3B side, loading coil L ₂ , stray capacitance C _c , and divide capacitor C ₃
Since all that is required is to resonate, the adjustment is extremely easy. In other words, the equivalent circuit of the resonance system of the oscillation circuit 4 and sensing plates 3A and 3B in FIG. 1 is shown in FIG. 2, and the resonance frequency on the oscillation circuit 4 side is
f ₀₁ is Therefore, the resonance frequency f ₀₂ of the sensing plates 3A and 3B is Therefore, it can be seen that it is sufficient to set f ₀₁ ≒ f ₀₂ .

Note that the sharpness Q of resistance _R4 decreases when an object that is not a pure conductor, such as a human, approaches, but when a conductor such as a metal approaches, the resistance becomes almost 0, so only the frequency This is to prevent the output level from increasing due to changes in the output voltage. Therefore, the resistor _R4 may be connected in series or in parallel with the loading coil _L2 .

In this way, when manufacturing the oscillation circuit 4, by determining the capacitance Ca from the relationship in equation (4) above, and adjusting the inductance of the loading coil _L2 , that is, the number of turns of the core, from the sensing plate capacitance _Cc , a highly sensitive automatic You can get a door switch. In addition, if the oscillation circuit is buried underground, stray capacitance C _c and leak resistance
R _c is added, but these effects are removed by the divide capacitors C ₂ and C ₃ . In other words, the oscillation frequency of the oscillation circuit 4 is determined by the capacitance Ca and the inductance _L1 , and if the inductance of the loading coil _L2 is adjusted according to the size of the stray capacitance _Cc to get closer to the oscillation frequency, the sensitivity can be improved. You can get a switch.

On the other hand, power is supplied to the oscillation circuit 4 via the power lines l1, l2 and the switch coils _L3 , _L4 , and a signal is supplied from the oscillation circuit 4 to the switch circuit 6 via the signal line l3 and the switch coil _L5 . Note that these choke coils L ₃ to _{L 5} play the role of completely preventing leakage of high frequency waves to the power supply section. The switch circuit 6 is composed of an automatic reset type amplifier section (for example, Japanese Patent Publication No. 56-22170) and a comparator section. At the same time, a capacitor C ₈ is connected to the inverting input terminal via a resistor R ₅ , and the output V ₀ of the DC amplifier 61 is input to one side of the comparator 62 and is connected to the inverting input terminal via a resistor R ₆ . It is applied to the inverting input terminal via the diode D ₂ to the connection point of the capacitor C ₈ and the resistor R ₅ . Further, the voltage from the variable resistor R7 is given to the other side of the comparator 62 as a reference, and the output of the comparator 62 is inputted to the base of the transistor Q2 via the resistor _R8 , and the collector of the transistor _Q2 is inputted to the base of the transistor _Q2 . The excitation winding RY of the relay is connected with a diode _D3 for surge absorption.
Therefore _, the output V ₀ of the DC amplifier 61 is as follows _, where V ₁ is the non-inverting input, _{V 2} is the inverting input, and A _{1 is} the amplification factor. be. However, if we consider the case where the charge on capacitor _C8 is 0, the inverting input is -V, so the output
V ₀ becomes V ₀ = (V ₁ −V) A ₁ ...(8). In other words, the output V ₀ is saturated at +V, and the output V ₀ begins to charge the capacitor C 8 through the diode D _2. When V ₁ ≒ V ₂ is reached, the output V ₀ becomes almost V ₁ , and the capacitor C ₈ is charged through the diode D ₂ . It stops charging. If there is a discharge due to the leakage current of the capacitor _C8 , this appears as a difference between (V ₁ - V ₂ ), and the output V ₀ becomes (V ₁ - V ₂ ) A ₁ , so it is immediately charged through the diode D ₂ . do. This is repeated, and the output V ₀ becomes almost a non-inverting input.
The voltage becomes stable at V ₁ . In this state the voltage V ₁
When V is changed by -ΔV ₁ , the difference between the inverting input and the non-inverting input becomes -ΔV ₁ since V ₁ = V ₂ ,
The output V ₀ is V ₀ = -ΔV ₁ A ₁ ...(9). Similarly, if the voltage V ₁ is changed by +ΔV ₁ , the output V ₀ becomes V ₀ = +ΔV ₁ A ₁ ...(10), but the capacitor C ₈ is changed through the diode D _2.
The output V ₀ is charged to the non-inverting input (V ₁
+ΔV ₁ ) and becomes stable. That is, when the non-inverting input changes in the positive direction, this DC amplifier 6
An output of 1 has an amplification factor of 1, and only in the case of a negative change, the amplification factor becomes A ₁ . Then, when changing in the negative direction,
The voltage charged in the capacitor _C8 is gradually discharged by the leakage voltage of the capacitor, the input impedance of the DC amplifier 61, etc., and when it drops by _ΔV1 , the difference between the inverting input and the non-inverting input becomes 0.
The output becomes stable at (V ₁ −ΔV ₁ ). In other words, since ΔV ₁ is a minute value, it can be considered that the state has almost returned to the state at the time of change, and the time period in between can be set appropriately.

Here, the output of the DC amplifier 61 is V ₁ ,
If the signal from the oscillation circuit 4 drops by ΔV ₁ , the output will be -ΔV ₁ A ₁ as described above,
This is input to one side of the comparator 62. Therefore, the reference voltage V ₃ is input from the variable resistor R ₇ to the other side, and V ₁ > V ₃ > ΔV ₁ ...(11) ΔV ₁ A ₁ > V ₃ ...(12) There is. In this way, when there is a change, V ₁ >
Since the voltage is V ₃ , the output of the comparator 62 becomes negative, and after the change, since V ₃ <ΔV ₁ A ₁ , the input difference is reversed, the output becomes positive, transistor Q ₂ is turned on, and the relay winding RY is energized and the door is opened via this relay contact. If the capacitor _C8 is connected in this state, the voltage across the capacitor C8 gradually decreases, and when it drops to _ΔV1 , the output of the DC amplifier 61 becomes ( _V1 - _ΔV1 ). In this state, the input to the next stage comparator 62 is V ₃ >
Since ΔV ₁ , the input is inverted again and V ₁ > V ₃
, its output becomes negative, transistor _Q2 is turned off, the excitation is cut off, and the door is closed.

In addition, the structure of the present invention, as shown in FIG. 3, is such that a printed circuit board circuit (oscillation circuit) 23 with an electronic element mounted thereon is arranged between two sensing plates 21 and 22, and after a predetermined adjustment operation, a molded circuit is installed. 24, which is buried underground near the automatic door. However, printed circuit board circuit 2
The signal from No. 3 is transmitted to the switch circuit in the manner described above, and the opening/closing of the door is controlled by this relay contact output. The size of the sensing plates 21 and 22 may be the same, but if the lower one is made larger as shown in the figure, the ground contact will be improved and the sensitivity will be increased. Furthermore, a printed circuit board circuit 23 and a sensing plate 2
1 and 22 may be made by soldering the lead wires, but as shown in Fig. 4, conductor coupling plates 25 and 26 are attached to the top and bottom of the side surfaces, and the sensing plate is directly sandwiched between these. It's okay. Note that although a Colpitts type oscillation circuit is shown above, this is arbitrary.

Effects of the invention: As described above, according to the present invention, the oscillation frequency can be easily adjusted near resonance,
The operation is also stable.

[Brief explanation of drawings]

FIG. 1 is a circuit connection diagram showing an embodiment of the invention, FIG. 2 is a diagram for explaining the principle of the invention, FIGS. 3 and 4 are diagrams showing an example of the structure of the invention, and FIG. 5A and 5B are structural diagrams showing how a conventional sensing plate device is embedded; FIGS. 6 to 8 are diagrams for explaining the operating principle of a sensing plate for automatic doors;
Figures 9A to 9C are diagrams for explaining the principle of automatic doors, Figure 10 is a diagram showing a dipole antenna, and Figure 11 is a circuit diagram when a Colpitts type oscillation circuit is arranged between sensing plates. . 3A, 3B, 30, 31, 41, 42...sensing plate, 6...switch circuit, 4, 40...high frequency oscillation circuit, _L2 ...loading coil, _L3 to _L5 ...
...Chiyoke coil, 61...DC amplifier, 62...
…comparator.

Claims (1)

[Claims] 1 two sensing plates, a high-frequency oscillation circuit disposed between the sensing plates, and a high-frequency oscillation circuit inserted between one of the sensing plates and the input section of the high-frequency oscillation circuit to reduce the stray capacitance of the sensing plates. a loading coil having a resonant inductance; and a loading coil for controlling the opening and closing of the door by detecting the output level of the high frequency oscillation circuit.
A proximity switch for an automatic door, comprising a switch circuit connected to the high frequency oscillation circuit, and a check coil inserted in a power line and a signal line, respectively, between the high frequency oscillation circuit and the switch circuit. Device.