JP2924070B2 - Proximity switch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a proximity switch used for detecting a metal ball such as a pachinko ball.

[Conventional technology]

2. Description of the Related Art Conventionally, in a pachinko game machine or the like, a proximity switch for detecting a pachinko ball is used in a passage path for detecting a pachinko ball. Such a proximity switch for pachinko balls has a Hartley-type oscillation circuit that oscillates at a constant frequency, a comparison circuit that compares the oscillation output thereof at a predetermined level, and an output circuit that processes the output and outputs it. doing. And when the metal ball does not pass, a certain level of oscillation is detected and output by the comparison circuit,
The metal sphere was detected by the decrease in amplitude accompanying the passage of the metal sphere.

[Problems to be solved by the invention]

However, in such a conventional proximity switch, when a relatively strong high-frequency radio wave is emitted in the proximity of the proximity switch, the oscillation of the oscillation circuit may be stopped, and the output is output as an erroneous detection of a metal ball. There was a drawback that sometimes.

The present invention has been made in view of such a problem of such a conventional proximity switch for detecting a metal ball, and when a radio wave is emitted in the vicinity, a metal object cannot be detected regardless of the presence or absence of the metal object. Is a technical task.

[Means for solving the problem]

The present invention is a proximity switch including an oscillation circuit having a resonance coil, and a comparison circuit that discriminates a decrease in oscillation output due to the proximity of an object with a predetermined threshold, wherein an output of the oscillation circuit is provided to a base thereof. A collector is formed as a substrate, the substrate is grounded, and the emitter is provided with an emitter follower circuit formed by a substrate type PNP transistor connected to a power supply via an emitter resistor. It is characterized by being connected to a comparison circuit via a circuit.

[Action]

According to the present invention having such features, by connecting a substrate type PNP transistor to the output side of the oscillation circuit, when radio waves oscillate in the vicinity of the oscillation circuit, the output sharply decreases. , The output supplied to the comparison circuit drops to the substrate potential (0 V in this case). Therefore, at that time, the detection of the metal object is prevented regardless of the presence or absence of the metal object.

〔Example〕

FIG. 1 is a block diagram showing a proximity switch according to an embodiment of the present invention. In this figure, the proximity switch has an oscillation circuit 2 to which a resonance circuit 1 is connected. Resonant circuit 1
, A detection coil is disposed close to the detection position of the object. The oscillating circuit 2 is, for example, a Hartley type oscillating circuit, which is supplied with a constant voltage and is always in an oscillating state. Then, the oscillation output is given to the substrate type PNP transistor Tr1. The collector of the substrate type PNP transistor Tr1 is common to the substrate, and the collector is grounded in the circuit, so that an emitter follower circuit is configured. The emitter of the transistor Tr1 is a resistor R
It is connected to the power supply via 1 and to the emitter of the NPN transistor Tr2 via the resistor R2. Transistor Tr2
Is connected to a voltage source 3 having a constant voltage V ₀ , for example, 2.8 V. The collector of the transistor Tr2 is connected to the base of the PNP transistor Tr3. Transistor Tr3
Is a switching transistor having an emitter connected to the power supply terminal and a collector serving as an output. Here the transistors Tr2, Tr3 is a voltage V ₀ as a threshold value, constitutes a comparator circuit 4 for comparing the level of the input signal and the this level.

Next, the configuration of the substrate type PNP transistor Tr1 according to the present embodiment in the IC will be described. FIG. 2 is a diagram showing a transistor Tr1 and its emitter resistance R1,
If the substrate of C is the P layer 10, the N layer 1
1 is formed. And the P layer 10 has P ⁺ up to the top of the IC.
Regions 12 and 13 are provided, and a metal electrode is arranged on the upper surface thereof and connected to the ground and the output terminal, respectively. An N ⁺ region 14 and a P ⁺ region 15 are provided adjacent to each other as a base and an emitter, respectively, in the N layer 11, and these constitute a substrate type PNP transistor Tr1. And N through the P ⁺ layer 13
A P ⁺ region 16 is formed as a resistor R1 in the region 11, and is connected to the P ⁺ region 15 as an emitter by a metal body. The P ⁺ layer 16 constituting the resistor R1 is connected to the power supply Vcc via the N ⁺ layer 17.

Next, the operation of the proximity switch according to the present embodiment will be described. FIG. 3A is a diagram showing the output of the emitter terminal of the transistor Tr1 and the output terminal of the comparison circuit 4 when a metal ball is intermittently passed near the coil of the resonance circuit 1. In this figure, when the metal ball does not pass through (T1), the oscillation circuit 2 oscillates at a constant frequency, and the amplitude waveform shown in FIG. 3A is obtained at the emitter of the transistor Tr1. Since the signal transistor Tr1 becomes the threshold value V ₀ below with concomitant intermittent is applied to the emitter of the transistor Tr2 in this state, the transistor Tr2 is also intermittently conductive. Therefore, as shown in FIG. 3 (b), the transistor Tr3 is turned on, the output is at a relatively low level, and a state in which the metal ball does not pass can be detected.

On the other hand, when the metal ball passes near the coil (T2), the oscillation circuit 2 stops oscillating as shown in FIG. Thus the emitter of the transistor Tr1 becomes a threshold greater than or equal _to V _0, the transistor Tr2 is turned off, the transistor Tr3 is also output turned off becomes H level, can detect the passage of the metal ball.

As shown in FIG. 4, when a strong electric wave, for example, an electric wave of 40 W at 430 MHz is irradiated near the coil of the oscillation circuit 2 in a state where the metal ball is intermittently passed (T3),
The substrate type PNP transistor Tr1 shown in the figure is shut off, and the emitter thereof has a low potential close to 0V. It is considered that this is because the substrate functions as one type of antenna and does not function as a transistor. In this way, during the radio wave irradiation period, the emitter potential of the transistor Tr1 drops sharply, and as shown in FIG.
2 is turned on, the transistor Tr3 is also turned on, and its output decreases. Therefore, regardless of the presence or absence of the passage of the metal sphere, an output for determining that there is no metal sphere is made. When the irradiation of the radio wave is stopped, the operation returns to the original operation.

FIG. 5 is a waveform diagram of each part showing a state in which a radio wave is interrupted while a metal ball is brought close to the resonance circuit 1. In this case, unless a radio wave is emitted, all the transistors Tr1 to Tr3 are turned off and a high level metal ball detection output is obtained. However, at the time of radio wave irradiation (T3), the emitter potential of the transistor Tr1 becomes 0 V. Then, the transistors Tr2 and Tr3 are turned on to output a state where there is no metal ball.

As described above, by using the substrate type PNP transistor in the present invention, it is possible to always output a state in which a metal sphere is not detected when a strong radio wave is irradiated.
Although the present embodiment describes a radio wave of 430 MHz and 40 W, the same effect can be obtained over a wide range from several tens of MHz to about 1000 MHz.

〔The invention's effect〕

As described in detail above, according to the present invention, when a strong radio wave is irradiated by using a substrate type PNP transistor, the emitter becomes 0 V, so that there is no metal object regardless of the presence or absence of the metal object passing Output can be obtained. Therefore, even when a strong radio wave, for which there has been no effective countermeasure in the past, is applied, the output can be reliably stopped.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a proximity switch according to one embodiment of the present invention, FIG. 2 is a configuration diagram in an IC showing a substrate type PNP transistor used in this embodiment, FIG.
FIG. 4 and FIG. 5 are waveform diagrams showing the waveform of each part of the proximity switch of this embodiment. 1 ... resonant circuit, 2 ... oscillation circuit, 3 ... voltage source, 4 ...
... Comparison circuit, 10 ... P layer (substrate), Tr1 ...
Substrate type PNP transistor, Tr2, Tr3 …… Transistor

Claims (1)

(57) [Claims] 1. A proximity switch comprising: an oscillation circuit having a resonance coil; and a comparison circuit that discriminates a decrease in oscillation output due to proximity of an object with a predetermined threshold value, wherein an output of the oscillation circuit is supplied to a base thereof. A collector is formed as a substrate, the substrate is grounded, and the emitter is provided with an emitter follower circuit formed by a substrate type PNP transistor connected to a power supply through an emitter resistor. A proximity switch connected to a comparison circuit via a follower circuit.