JP2536148B2 - Proximity switch identification device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a discriminating device in a proximity switch for discriminating whether or not a metal to be detected has approached a coil within a magnetic flux generated by the coil which constitutes an attenuating resonant circuit with a coil and a capacitor, particularly a switch for a proximity switch. The present invention relates to a proximity switch discriminating apparatus that can improve the detection accuracy of a switch regardless of variations in components. In the drawings below, the same reference numerals indicate the same or corresponding parts.

[Prior art]

FIG. 2 is a circuit diagram showing a configuration example of this type of proximity switch (device), and FIG. 3 is a waveform diagram of the operation explanatory diagram of FIG. In FIG. 2, L is a coil for determining whether or not the metal to be detected approaches itself within the generated magnetic flux, C is a capacitor connected in parallel to this coil L to form a resonance circuit,
R1 is a resistor for limiting the energization current of the coil L, and S1 is a transistor that is driven through the pulse counting control circuit 2 to open and close the current of the coil L. Further, R2 and R3 are voltage dividing resistors for obtaining the reference voltage VF from the DC body voltage power supply VCC, and 3 is the voltage of the resonance circuit (in this example, the voltage at the connection point P between the resistor R1 and the transistor S1) and the reference voltage VF. It is a comparison circuit for comparing with. Reference numeral 2 denotes a pulse counting control circuit for opening and closing the transistor S1 and pulse counting, and 11 is a counter belonging to this circuit 2 for counting the output 3a of the comparison circuit 3. Now, when the transistor S1 is turned on for a predetermined time to establish a predetermined current in the coil L that is determined by the DC voltage VCC and the resistance R1, the transistor S1 is turned off, and the potential at the point P is as shown in Fig. 3 (1). In addition, it has a damping vibration waveform that vibrates up and down around the potential VCC. The comparison circuit output 3a obtained by comparing the P-point potential and the reference voltage VF via the comparison circuit 3 is as shown in FIG. 3 (1) and 3 (2), the waveforms on the left side show the case where there is no metal, that is, the case where the metal to be detected does not approach the coil L, and the waveforms on the right side also have metal, that is, the case where the metal to be detected to the coil L The case where a metal approaches is shown. In this way, the resonance waveform decays faster (stronger) as the metal to be detected approaches. This is because the change of the magnetic flux generated by the coil L causes an overcurrent to flow in the metal to be detected which is close to the coil L. In this way, when the pulse output as the comparison circuit output 3a is counted through the counter 11, this count value becomes smaller when the metal to be detected is approaching than when it is not approaching. Therefore, conventionally, the count output (pulse number) A of the counter 11 is compared with one threshold value (N) through the count N discriminating means 12 of FIG. 1, and if the pulse number A is N or more, there is no metal and less than N. If so, it was determined that there was metal.

[Problems to be Solved by the Invention]

However, in the conventional proximity switch, since the count value of the counter 11 is compared with the fixed numerical value N, the attenuation waveform varies due to the variation of Q of the co-advance circuits L and C, and thus the operation of switching the presence or absence of metal. The points were different due to the proximity switch, and it was not possible to realize a highly accurate proximity switch. Therefore, the present invention provides the count value of the counter when adjusting the proximity switch in advance, when there is no metal to be detected in the bundle when the detection coil is generated, or when the metal to be detected is placed at a desired position where detection should be performed. A threshold value as a value obtained by subtracting a predetermined value from the value stored in this memory, which is stored in the memory and detected and output when actually used as a proximity switch, or the value stored in the memory. An object of the present invention is to solve the above-mentioned problem by providing a determination device for a proximity switch that determines the presence or absence of metal by comparing it with a threshold value.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the device of the present invention is configured such that “a coil (L or the like) arranged so that the metal to be detected can enter the magnetic flux created by itself and a capacitor (C or the like) are connected in parallel. To form a resonance circuit, and after applying a predetermined bias to this resonance circuit via a DC power supply (such as VCC) (using transistor S1, resistor R1 etc.), disconnect the DC power supply from this resonance circuit, After disconnection, the wave number of the damped resonant wave generated until the current or voltage of the coil or the capacitor is damped to a predetermined level is calculated (this wave number is obtained through the comparison circuit 3, counter 11, etc.). In a proximity switch that determines whether or not the detected metal is close to the coil (via the pulse counting control circuit 2 or the like) by comparing with a predetermined count threshold value, a predetermined state (the detected metal is a coil Occurrence of L The number of the damped resonant wave generated as described above is stored and stored (via the writing means 13 or the like) in a state where it is not in the bundle, or in a state where the metal is placed at a desired position to be detected). Means (memory 15 or the like) and the stored value (M or the like) are used to set the counting threshold value (as a value M-α obtained by subtracting a predetermined value α from the stored value M or a stored value M). Means (writing means 14, count value discriminating means 12A, etc.).

[Work]

When there is no metal to be detected in the surroundings, it is judged that there is metal when the count value changes by a predetermined value or more, or when the count value when used as a proximity switch is actually detected metal. The presence or absence of the proximity of the metal is determined by comparing with the count value when the metal is placed at the proper position, and the proximity detection of the metal with high accuracy is performed.

【Example】

Next, an embodiment of the present invention will be described with reference to FIG. This drawing is a circuit diagram showing a configuration as an embodiment of the present invention and corresponds to FIG. In FIG. 1, the pulse counting control circuit is replaced with a new circuit 2A as compared with FIG. 2, and the count value discriminating means 12A, writing means 13, reading means 14 are provided in this circuit 2A.
Is newly established. Further, a memory 15 is added outside the circuit 2A. Next, the operation of FIG. 1 will be described with reference to two embodiments.
First, as a first embodiment, when the proximity switch is adjusted in advance, the number of output pulses 3a of the comparison circuit 3 is counted by the counter 11 in a state where there is no metal to be detected in the magnetic flux generated by the detection coil L, and the count value is obtained. M is written in the memory 15 via the writing means 13 and placed. In this case, when actually used as a proximity switch, the value M written in the memory 15 by the reading means 14 is loaded into the count value judging means 12A, and the judging means 12A outputs the number of output pulses 3a of the comparison circuit 3a. Is compared with a threshold value M-α defined as a value obtained by subtracting a predetermined value α from M, and when A ≧ M-α, no metal, A <M-α When it is determined that there is metal. In the second embodiment, similarly, when the proximity switch is adjusted, the detected metal is placed at a desired position where the proximity of the detected metal should be detected, and the output pulse number 3a of the comparison circuit 3 at this time is counted. The value is counted in 11 and the counted value M is written in the memory 15 via the writing means 13 and stored.
In this case, when actually used as a proximity switch, the value M written in the memory 15 by the reading means 14 is loaded as a threshold value into the count value determining means 12A, and the threshold value M is determined by the determining means 12A. Is compared with the count value A of the counter 11 that has counted the output pulse number 3a of the comparison circuit 3, and when A ≧ M, it is determined that there is no metal, and when A <M, there is metal.

【The invention's effect】

According to the present invention, when the proximity switch is adjusted, the counter count value output when there is actually no metal around the detection coil is stored in advance, and when the proximity switch is used, the detected count value is stored. When it is smaller than the stored count value by a predetermined value or more, it is determined that there is metal, or when the proximity switch is adjusted, when the metal to be detected is placed at the position where the proximity of the metal should be actually detected. The output count value is stored and stored, and when it is used as a proximity switch, the detected count value is compared with the threshold value as the stored count value. Not only the variations but also the variations of R1, R2, and R3 can be effectively corrected, and a highly accurate proximity switch can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration as one embodiment of the present invention, FIG. 2 is a corresponding conventional circuit diagram, and FIG. 3 is a waveform diagram for explaining the operation of FIG. 2A: Pulse counting control circuit, 3: Comparison circuit, 3a: Comparison circuit output, VCC: DC constant voltage power supply, L: Coil, C: Capacitor, R
1, R2, R3: resistance, S1: transistor, VF: reference voltage, 11: counter, M, A: count output (pulse number), 12A: count value discriminating means, 13: writing means, 14: reading means, 15: Memory.

Claims (1)

(57) [Claims] 1. A resonance circuit is constructed by connecting a coil and a capacitor arranged in parallel so that the metal to be detected can enter the magnetic flux created by the resonance circuit, and the resonance circuit is connected to the resonance circuit via a direct current power source. After energizing, the DC power supply is disconnected from the resonant circuit, and after this disconnection, the wave number of the damped resonant wave generated until the current or voltage of the coil or the capacitor is damped to a predetermined level is set to a predetermined value. A proximity switch for determining whether or not the detected metal is in proximity to the coil by comparing with a counting threshold, and means for storing and storing a fraction of the damped resonant wave generated as described above in a predetermined state in advance. And a means for setting the counting threshold value using the stored value, and a proximity switch discriminating apparatus.