JPH02213221A - Fault discrimination method for proximity switch - Google Patents

Abstract

PURPOSE:To discriminate a fault of a proximity switch such as a broken coil wire by setting two large and small threshold levels as count threshold levels and discriminating it that the proximity switch is faulty when the level is lower than the smaller threshold level. CONSTITUTION:A transistor(TR) S1 is turned on to activate an LC circuit. When the TR S1 is turned off, the LC resonance circuit starts the oscillation. Number of pulses 3a as the comparison output outputted from a comparator circuit 3 is counted via a counter 11 while a prescribed time (y) is counted and its count is stored in the counter 11. When a count N discriminating means 12 discriminates the count output (pulse number) 11a of the counter 11 to be, for example, 15 or over, it is discriminated that 'no coin' is deposited. On the other hand, when the count N discriminating means 12 discriminates the pulse number 11a of the counter 11 to be less than 15, a count 0 discrimination means 13 discriminates whether or not the pulse number 11a is 0 and if it is discriminated to be 0, then it is regarded as a broken wire of a coil L, and 'faulty switch' is decided.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention provides a method for determining whether or not a metal to be detected approaches the coil within the magnetic flux generated by the coil, which constitutes a damped resonant circuit by a coil and a capacitor, based on the speed of attenuation of the resonance. The present invention relates to a method for determining an abnormality such as a coil disconnection in a switch. Note that in the following figures, the same reference numerals indicate the same or corresponding parts. rPrior Art] Fig. 1 is a circuit diagram showing the configuration of an embodiment of the proximity switch (device) of the present invention, and this drawing will be used hereinafter, and the conventional technology will be explained using Fig. 4. do. In the prior art, the count 0 determining means 13 shown in FIG. 1 is not provided, and FIG. 4 is a waveform diagram for explaining the operation of FIG. 1. In Figure 1, L is a coil that determines whether the metal to be detected approaches itself within the generated magnetic flux, C is a capacitor connected in parallel to this coil to form a resonant circuit, and R
1 is a resistor for limiting the current flowing through the coil L, and SI is a transistor that is driven via the pulse counting control circuit 2 to open and close the current of the coil L. Also R2. R3 is a voltage dividing resistor for obtaining the reference voltage VF from the DC constant voltage power supply ■CC, and 3 is a voltage dividing resistor for comparing the voltage of the resonant circuit (in this example, the voltage at the connection point between the resistor R1 and the transistor S1) and the reference voltage VF. This is a comparison circuit that 2 is a pulse counting control circuit for opening/closing the transistor S1 and counting pulses, and 11 is a counter belonging to this circuit 2, which counts the output 3a of the comparison circuit 3. Now, when transistor S1 is turned on for a predetermined period of time to establish a predetermined current determined by the DC voltage CC and resistor R1, the potential at point P becomes as shown in Figure 4 (1). A damped oscillation waveform oscillates above and below the potential vCC as the center. The comparison circuit output 3a obtained by comparing this P point potential and the reference voltage VF via the comparison circuit 3 is as shown in FIG. 4(2). In Fig. 4 (1) and (2), the waveforms on the left side indicate the case where there is no metal, that is, there is no detected metal approaching the coil L, and the waveforms on the right side indicate the case where there is metal, that is, the case where the detected metal does not approach the coil L. Indicates a case where there is close contact with metal. In this way, the attenuation of the resonance waveform becomes faster (stronger) as the metal to be detected approaches. This is because an eddy current flows in the metal to be detected close to the coil due to a change in the magnetic flux generated by the coil L. When the pulse output as the comparison circuit output 3a is counted by the counter 11 in this manner, the counted value becomes smaller when the metal to be detected approaches than when it does not approach. Therefore, conventionally, the count output (pulse number) 11a of the counter 11 is compared with one threshold value (N) via the count N discrimination means 12 shown in FIG. In that case, it was determined that there was metal.

[Problem to be solved by the invention]

In this type of proximity switch, disconnection of the coil L is often the cause of failure. Conventionally, when the coil L is disconnected, the LC shown in Figure 1
The circuit no longer oscillates, and as a result, the comparator circuit 3 no longer outputs pulses. Therefore, conventionally, when a coil is disconnected, there has been a problem in that it is determined that metal is present because the pulse number 11a is less than N regardless of the presence or absence of metal. Therefore, the present invention adds a second small threshold (0) in addition to the conventional large threshold (N) when processing the counted pulse number 11a to determine the presence or absence of a pulse. It is an object of the present invention to solve the above problem by providing a method for determining an abnormality in a proximity switch.

[Means to solve the problem]

In order to solve the above problems, the method of the present invention uses a coil (L, etc.) disposed (near the change cylinder 01, etc.) so that the metal to be detected (coin, etc.) can enter the magnetic flux generated by r itself. ) and a capacitor (such as C) are connected in parallel to form a resonant circuit, and this resonant circuit is energized to a predetermined value using a transistor 31, a resistor R1, etc. via a DC power supply (VCC, etc.). After that, the DC power source is disconnected from this resonant circuit, and after this disconnection, the wave number of the attenuated resonant wave that occurs until the current or voltage of the coil or capacitor attenuates to a predetermined level is calculated (comparison circuit 3. 11, etc., and compares this wave number with a predetermined counting threshold value to determine (via pulse counting control circuit 2, etc.) whether or not the detected metal is close to the coil. Swish. In H, the counting threshold is large (such as 15) or small (such as 0).
two threshold values are set, and when the wave number exceeds the large threshold value (this is determined through the counting N determining means 12 or the like), it is determined that the metal to be detected is not in the vicinity; The wave number is the above two large and small wave numbers.
between two threshold values (counting N discriminating means 12,
If the detected metal is in the vicinity (as determined by the counting O discrimination means 13 or the like), it is determined that the detected metal is in the vicinity, and the wave number is below the small threshold value (this is determined through the counting O discrimination means 13 or the like). In this case, it is set to 1 to determine that there is an abnormality in this proximity switch (such as a disconnection of the coil L).

[For use]

Since a wave number of 0 means that the LC resonant circuit is not oscillating, it is possible to determine an abnormality in the proximity switch such as coil breakage by determining this 0.

【Example】

The present invention will be described in detail below with reference to FIGS. 1 to 3. In FIG. 1, in the present invention, the pulse counting control circuit 2
A counting O discrimination means 13 is newly installed within the unit. FIG. 2 shows a configuration in which the present invention is specifically applied to a change detection switch of a coin mechanism. In the figure, the coil L portion of the proximity switch 1 is installed near the change tube O1 of the coin mechanism. Note that the proximity switch 1 here refers to the portion excluding the pulse counting control circuit 2 in FIG. 1, that is, a proximity switch in a narrow sense, and the pulse counting circuit 2 in FIG. 2 has the same configuration as the circuit 2 in FIG. 1. However, in FIG. 2, it is included in the control circuit of the main body of the coin mechanism. However, in a broader sense, that is, in the present invention, the proximity switch refers to the entirety of FIG. 1, and when it is intentionally called to distinguish it, it is called a proximity switch device. FIG. 3 is a flowchart showing the operation of the pulse counting control circuit 2 in the example of FIG. Next, the operation of the pulse counting control circuit 2 shown in FIGS. 1 and 2 will be explained using FIG. 3. In addition, in the following explanation (2-1) ~
Numbers (2-13) indicate step numbers in FIG. First, in (2-1), the transistor S1 is turned ON and the LC circuit is energized. In other words, the DC constant voltage power supply ■CC causes the coil L to
Wait for the software timer A to measure a predetermined time X until the current of is established to approximately the value determined by the resistor R1 (2
-2), the counter 11 is cleared for later pulse counting in (2-3). Next, when the transistor S1 is turned off in (2-4), the LC resonant circuit starts oscillating. In the following steps (2-5) to (2-6), until the software timer B counts a predetermined time y, the number of pulses 3a as a comparison output output from the comparison circuit 3 is counted by the counter 11. and stores the counted value in the counter 11. (2-7) and subsequent steps are data processing. That is, if the counting ratio (number of pulses) of the counter 11 is determined to be 15 or more in (2-7), then
On the other hand, if the counting N determining means 12 determines that the pulse number 11a is less than 15,
In (2-9), the counting O discrimination means 13 sets the pulse number 11a to 0.
If it is 0, it is assumed that the coil L is disconnected and
It is determined that the switch is abnormal (2-10). At the same time, since the presence or absence of coins is uncertain, it is determined that there is no coin (2-11)
. On the other hand, if the count 0 determining means 13 determines that it is not O in the above (2-9), it is determined that "coins are present" (2-12
), and finally, in (2-13), software timers A and B are cleared for the next measurement. In addition, the measurement result of the counting output 11a when using an actual coin is 20 pulses without a coin, and a copper coin (10 yen).
There are 12 pulses when a cupronickel coin (100 yen, etc.) is present, and 10 pulses when a cupronickel coin (100 yen, etc.) is present, indicating that the above determination method is effective.

【Effect of the invention】

According to the present invention, a resonant circuit is formed by connecting the coil L, which is disposed so that the metal to be detected can enter the magnetic flux it generates, and the capacitor C in parallel, and the transistor S1 is
NL DC power supply ■ After energizing this resonant circuit by passing a predetermined current through CC, transistor S1 is turned off.
F to disconnect the DC power supply ■CC from this resonant circuit,
After this disconnection, the wave number of the attenuated resonant wave generated until the voltage of the coil or capacitor attenuates to a predetermined level determined by the power supply voltage CC and the reference voltage VF was determined by the comparison circuit 3 and the counter 11. In a proximity switch that compares the wave number of this wave with a predetermined counting threshold to determine whether or not the detected metal is close to the coil, the counting threshold may be large (such as 15) or small (such as O). and)
two threshold values are set, and when the wave number exceeds the large threshold, it is determined that there is no proximity of the detected metal, and when the wave number is between the two large and small thresholds, When the wave number is below the small threshold value, it is determined that there is a proximity of the metal to be detected, and when the wave number is below the small threshold value, it is determined that there is an abnormality in the proximity switch. When a wire breaks, regardless of the presence or absence of metal, it is determined that there is metal, that is, there is change, so it is fine as long as there is change, but if there is no change, it will be impossible to pay out change. According to the present invention, such a situation can be avoided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the main part configuration as an embodiment of the present invention, FIG. 2 is a configuration diagram when the present invention is applied to a coin mechanism, and FIG. 3 is a pulse diagram in FIGS. 1 and 2. A flowchart showing the operation of the counting control circuit, and FIG. 4 is a waveform diagram for explaining the operation of FIG. 1. 01: Change cylinder, 2: Pulse counting control circuit, 3: Comparison circuit, 3a: Comparison circuit output, VCC: DC constant voltage power supply, L
: Coil, C: Capacitor, R1, R2゜R3: Resistor,
SL: Transistor, vF: Reference voltage, 11: Counter, 11a: Count output (number of pulses), 12: Count N discrimination means, 13: Count O discrimination means. Direct determination, voltage diagram 1 diagram 2

Claims (1)

[Claims] 1) A coil arranged so that the metal to be detected can enter the magnetic flux it generates and a capacitor are connected in parallel to form a resonant circuit, and this resonant circuit is connected via a DC power source. The wave number of the attenuated resonant wave that occurs after the DC power source is disconnected from the resonant circuit after a predetermined energization is applied to the coil or capacitor until the current or voltage in the coil or capacitor attenuates to a predetermined level. in a proximity switch that determines whether the metal to be detected is in proximity to the coil by comparing it with a predetermined counting threshold; two thresholds, large and small, are set as the counting threshold; When the wave number exceeds the large threshold, it is determined that the metal to be detected is not in proximity, and when the wave number is between the two large and small thresholds, it is determined that the metal to be detected is not in proximity. A method for determining an abnormality in a proximity switch, characterized in that the proximity switch is determined to have an abnormality when the wave number is less than the small threshold value.