JP2021110549A - Proximity sensor - Google Patents

Abstract

To provide a proximity sensor that can increase a detectable distance of a detection target made of metal.SOLUTION: A proximity sensor comprises: an oscillator circuit 10 having an oscillation coil 11, which outputs an oscillation signal having an amplitude that is attenuated as a detection target made of metal approaches to the oscillation coil 11; an oscillation control circuit 20 that has a magnetic field detection element 21 whose impedance changes according to a change of intensity of a magnetic field due to an interaction between the detection target and the oscillation coil 11, and that decreases the amplitude of the oscillation signal according to the amount of the change of the impedance of the magnetic field detection element 21; and a determination circuit 30 that determines whether or not the detection target is detected by comparing a signal value corresponding to the amplitude of the oscillation signal outputted from the oscillation control circuit 20 with a prescribed threshold level.SELECTED DRAWING: Figure 1

Description

The present invention relates to a proximity sensor.

A proximity sensor using an oscillation circuit including an oscillation coil has been proposed in order to detect the approach of an object to be detected (hereinafter, simply referred to as a detection object) formed of metal (for example, Patent Document 1). reference). In the technique described in Patent Document 1, the oscillation circuit oscillates when the object to be detected is away from the leakage magnetic field of the oscillation coil, while the conductance of the oscillation coil increases by approaching the leakage magnetic field of the oscillation coil. Therefore, the oscillation condition of the oscillation circuit is no longer satisfied, and the oscillation circuit is in the oscillation stop state. As a result, the object to be detected is detected.

Further, in order to increase the sensitivity of the proximity sensor, a technique using a magnetic impedance element has been proposed (see, for example, Patent Document 2). In the technique described in Patent Document 2, a magnetic impedance element is arranged inside the exciting coil, and the eddy current magnetic flux from the metal body is detected by the magnetic impedance element. Further, the oscillation frequency is set so that an eddy current magnetic flux whose phase is delayed by 90 degrees with respect to the exciting magnetic flux is generated, and the timing control circuit is centered on the time when the exciting current from the exciting oscillation circuit becomes zero. A sampling pulse is generated in a predetermined period. Then, the output from the magnetic impedance element during the output period of the sampling pulse is integrated, the integration result is accumulated in the differential amplifier circuit, and then compared with a predetermined threshold value in the comparator.

Japanese Unexamined Patent Publication No. 4-25218 Japanese Unexamined Patent Publication No. 2003-273718

However, in the technique described in Patent Document 1, the structure of the proximity sensor becomes too complicated in order to increase the sensitivity of the proximity sensor, so that the detection target is a detectable distance (hereinafter, simply referred to as a detectable distance). May not be enough. Further, since the magnetic force of the metal itself is very weak, the signal-to-noise ratio in the output signal from the magnetic impedance element is not good in the technique described in Patent Document 2. Therefore, even with this technique, the detectable distance may not be sufficiently obtained.

Therefore, an object of the present invention is to provide a proximity sensor capable of increasing the detectable distance of a detection object formed of metal.

A proximity sensor is provided as one embodiment of the present invention. This proximity sensor is based on the interaction between an oscillating circuit that has an oscillating coil and outputs an oscillating signal having an amplitude that attenuates as the detection object formed of metal approaches the oscillating coil, and the oscillating object and the oscillating coil. An oscillation control circuit that has a magnetic field detection element whose impedance changes according to a change in the strength of the magnetic field and reduces the amplitude of the oscillation signal according to the amount of change in the impedance of the magnetic field detection element, and an oscillation control circuit that outputs the oscillation signal. It has a determination circuit for determining whether or not a detection target is detected by comparing a signal value corresponding to the amplitude of an oscillation signal with a predetermined threshold value.
By having such a configuration, the proximity sensor can increase the distance at which a detection object formed of metal can be detected. Further, by separately providing the oscillation coil and the magnetic field detection element, this proximity sensor sets the distance at which the detection target can be detected in the direction in which the oscillation coil and the magnetic field detection element are lined up, and the detection target in the other direction. Can be made larger than the detectable distance, that is, directional with respect to the detection direction.

In this proximity sensor, the oscillation control circuit is connected between the oscillation circuit and the determination circuit, and the voltage divider circuit that can reduce the amplitude of the oscillation signal by dividing the oscillation signal and the impedance of the magnetic field detection element It has a switching element that causes the voltage divider circuit to divide the oscillation signal when the amount of change exceeds a predetermined threshold, and does not cause the voltage divider circuit to divide the oscillation signal when the amount of change in the impedance of the magnetic field detection element is less than the predetermined threshold. Is preferable.
As a result, the proximity sensor can set a predetermined threshold value in advance according to the application of the proximity sensor, so that the distance between the detection object and the oscillation coil whose amplitude of the oscillation signal is reduced by the magnetic field detection element can be set. The distance at which the detection target can be detected can be set appropriately.

Alternatively, in this proximity sensor, the oscillation control circuit causes an oscillation signal amplitude by passing a constant amount of current from the oscillation circuit to a predetermined circuit other than the oscillation coil when the amount of change in the impedance of the magnetic field detection element exceeds a predetermined threshold value. When the amount of change in the impedance of the magnetic field detection element becomes less than a predetermined threshold value, it is preferable to suppress the decrease in the amplitude of the oscillation signal by stopping the outflow of current from the oscillation circuit to the predetermined circuit.
As a result, the proximity sensor can set a predetermined threshold value in advance according to the application of the proximity sensor, so that the distance between the detection object and the oscillation coil whose amplitude of the oscillation signal is reduced by the magnetic field detection element can be set. The distance at which the detection target can be detected can be set appropriately.

Alternatively, in this proximity sensor, the oscillating circuit further has an oscillating circuit body that supplies a current to the oscillating coil, and the magnetic field detecting element reduces the strength of the magnetic field due to the interaction between the object to be detected and the oscillating coil. It is preferable that the impedance increases as the frequency increases and the oscillation coil is connected to the main body of the oscillation circuit.
As a result, the proximity sensor can increase the distance at which the object to be detected can be detected with a simple circuit configuration.

Alternatively, in this proximity sensor, the oscillating circuit further has an oscillating circuit body that supplies a current to the oscillating coil, and the magnetic field detecting element reduces the strength of the magnetic field due to the interaction between the object to be detected and the oscillating coil. It is preferable that the impedance is lowered as much as possible, and the oscillation circuit body is connected in parallel with the oscillation coil.
As a result, the proximity sensor can increase the distance at which the object to be detected can be detected with a simple circuit configuration.

As another embodiment of the present invention, a proximity sensor is provided. This proximity sensor has an oscillating coil formed by a magnetic impedance element, and as the detection object formed of metal approaches the oscillating coil, the amount of change in impedance by the magnetic impedance element and between the detection object and the oscillating coil. By comparing an oscillating circuit that outputs an oscillating signal with an amplitude that decays according to the amount of change in the strength of the magnetic field due to interaction, and a signal value according to the amplitude of the oscillating signal from the oscillating circuit and a predetermined threshold value. It has a determination circuit for determining whether or not a detection object has been detected.
By having such a configuration, the proximity sensor can increase the distance at which a detection object formed of metal can be detected. Further, since the oscillation coil itself is formed by the magnetic impedance element, the proximity sensor can be miniaturized and the directivity regarding the detection direction can be suppressed.

It is a circuit block diagram of the proximity sensor by one Embodiment of this invention. It is a figure which shows an example of the change of the waveform of the oscillation signal from the oscillation circuit which a proximity sensor has, and the waveform of the oscillation signal which passed through an oscillation control circuit, according to the change of the distance between a detection object and a proximity sensor. It is an external perspective view of a proximity sensor. It is an exploded perspective view of a proximity sensor. It is a side view of the circuit board of a proximity sensor. (A) is an external perspective view of a flow path of a game ball showing an example of arrangement of proximity sensors in a gaming machine having a proximity sensor. (B) is a cross-sectional view of the flow path in the line seen from the arrows A and A'sides in (a). It is a circuit block diagram of the proximity sensor by the modification. It is a circuit block diagram of the proximity sensor by another modification. It is a circuit block diagram of the proximity sensor by still another modification. It is an equivalent circuit diagram of an oscillation circuit and a detection object in the modification shown in FIG. It is an external perspective view of the proximity sensor in the modification shown in FIG. It is an exploded perspective view of the proximity sensor in the modification shown in FIG.

Hereinafter, the proximity sensor according to one embodiment of the present invention will be described with reference to the drawings. This proximity sensor determines the presence / absence of an object to be detected by comparing a signal value corresponding to the amplitude of an oscillation signal output from an oscillation circuit having an oscillation coil with a threshold value. This proximity sensor further includes a magnetic field detecting element whose impedance changes according to the strength of the magnetic field due to the interaction between the object to be detected and the oscillating coil. When the impedance of the magnetic field detection element becomes equal to or higher than a predetermined threshold due to the approach of the detection object, this proximity sensor suppresses the amplitude of the oscillation signal output from the oscillation circuit, thereby suppressing the amplitude of the oscillation signal, thereby corresponding to the amplitude of the oscillation signal. Increase the distance between the oscillating coil and the detection object, that is, the detectable distance, at which the value is equal to or less than the threshold value.

FIG. 1 is a circuit configuration diagram of a proximity sensor according to one embodiment of the present invention. The proximity sensor 1 includes an oscillation circuit 10, an oscillation control circuit 20, and a determination circuit 30.

The oscillation circuit 10 is a feedback type oscillation circuit using an LC circuit composed of an oscillation coil 11 and a resonance capacitor 12, and can be, for example, a Hartley oscillation circuit or a Colpitts oscillation circuit. Therefore, the oscillation circuit 10 includes an oscillation coil 11, a resonance capacitor 12 connected in parallel with the oscillation coil 11, and an oscillation circuit main body 13 that supplies a current to the oscillation coil 11 and the resonance capacitor 12. Then, the oscillation circuit 10 outputs an oscillation signal to the oscillation control circuit 20.

Here, as the detection object 100 approaches the oscillation coil 11, the loss due to the eddy current generated in the detection object 100 increases, so that the strength of the magnetic field in the vicinity of the oscillation coil 11 decreases. As a result, the oscillation conditions of the oscillation circuit 10 fluctuate. Therefore, the amplitude of the oscillation signal output from the oscillation circuit 10 is attenuated as the detection object 100 approaches the oscillation coil 11. From this, the proximity sensor 1 can determine the presence / absence of the detection target 100 based on the change in the amplitude of the oscillation signal output from the oscillation circuit 10.

The oscillation control circuit 20 has a magnetic field detection element 21, and an oscillation signal from the oscillation circuit 10 is detected by the magnetic field detection element 21 according to the strength of the magnetic field due to the interaction between the detection object 100 and the oscillation coil 11. Control the amplitude of. In the present embodiment, the oscillation control circuit 20 reduces the amplitude of the oscillation signal from the oscillation circuit 10 when the impedance of the magnetic field detection element 21 exceeds a predetermined value. Therefore, the oscillation control circuit 20 includes a voltage dividing circuit 22 in which one of the two resistors is a magnetic field detecting element 21, and a switching element 23 that can be turned on / off by the output voltage from the voltage dividing circuit 22. The voltage dividing circuit 24 is connected between the switching element 23 and the output terminal of the oscillation circuit 10.

The magnetic field detection element 21 is an element whose impedance changes according to a change in the strength of the magnetic field due to the interaction between the oscillation coil 11 and the detection object 100. In the present embodiment, the magnetic field detection element 21 is an element whose impedance increases as the strength of the magnetic field due to the interaction between the oscillation coil 11 and the detection object 100 decreases, and for example, an amorphous alloy wire or a magnetic thin film is used. It can be a configured magnetic impedance element. Then, the magnetic field detection element 21 can detect, for example, the assumed closest position of the detection object 100 with respect to the oscillation coil 11 and the oscillation coil 11 so that the magnetic field strength change due to the interaction between the oscillation coil 11 and the detection object 100 can be detected. It is placed between and. The details of the arrangement of the oscillation coil 11 and the magnetic field detection element 21 will be described later.

In the present embodiment, the impedance of the magnetic field detection element 21 decreases as the strength of the magnetic field in the vicinity of the oscillation coil 11 decreases in response to the loss due to the eddy current generated in the detection object 100 when the detection object 100 approaches the oscillation coil 11. Will increase. The details will be described later, but the amount of change in the impedance of the magnetic field detection element 21 with respect to the impedance of the magnetic field detection element 21 (hereinafter referred to as the reference impedance) when the detection object 100 does not act on the magnetic field near the oscillation coil 11 is predetermined. When the value exceeds the threshold value of, the oscillation control circuit 20 suppresses the amplitude of the oscillation signal output from the oscillation circuit 10.

The magnetic field detection element 21 may have a magnetoresistive element or a coil instead of the magnetic impedance element. In this case as well, the magnetic field detection element 21 may be configured so that the impedance increases as the strength of the magnetic field in the vicinity of the oscillation coil 11 decreases due to the interaction between the oscillation coil 11 and the detection object 100.

The voltage dividing circuit 22 is composed of a resistor R0 having one end connected to the voltage source Vcc and the other end connected to the magnetic field detecting element 21, and the magnetic field detecting element 21. In the voltage divider circuit 22, one end of the magnetic field detection element 21 is connected to the other end of the resistor R0, and the other end of the magnetic field detection element 21 is grounded. Then, the voltage V supplied from the voltage source Vcc from between the other end of the resistor R0 and one end of the magnetic field detection element 21 is the sum of the impedance of the resistor R0 and the impedance of the magnetic field detection element 21. The voltage obtained by dividing the voltage by the impedance ratio is output. Therefore, the higher the impedance of the magnetic field detection element 21, that is, the lower the strength of the magnetic field in the vicinity of the oscillation coil 11, the higher the voltage output from the voltage dividing circuit 22. Further, the impedance of the resistor R0, that is, the amount of change in the impedance of the magnetic field detection element 21 from which the switching element 23 is turned on from the reference impedance is set in advance according to the application of the proximity sensor 1, so that the magnetic field detection element 21 can be used. Since the distance between the detection object 100 and the oscillation coil 11, which reduces the amplitude of the oscillation signal from the oscillation circuit 10, can be appropriately set, the proximity sensor 1 appropriately sets the distance at which the detection object 100 can be detected. be able to.
The resistor R0 may be a variable resistor whose impedance can be adjusted. In this case, the proximity sensor 1 adjusts the impedance of the resistor R0 to change the impedance of the magnetic field detection element 21 in which the switching element 23 is turned on, that is, the threshold value for the amount of change in impedance from the reference impedance. Can be done. That is, the detectable distance of the proximity sensor 1 can be adjusted.

The switching element 23 is, for example, an npn type transistor, the base terminal is connected to the voltage dividing circuit 22, the collector terminal is connected to the voltage dividing circuit 24, and the emitter terminal is grounded. The on / off of the switching element 23 is switched according to the voltage output from the voltage dividing circuit 22. The switching element 23 may be an n-channel MOSFET. In this case, the gate terminal may be connected to the voltage dividing circuit 22, the drain terminal may be connected to the voltage dividing circuit 24, and the source terminal may be grounded.

In the present embodiment, as described above, the higher the impedance of the magnetic field detection element 21, the higher the voltage output from the voltage dividing circuit 22, and when the impedance of the magnetic field detection element 21 becomes equal to or higher than a predetermined threshold value, the switching element 23 Turns on. In this case, the oscillation signal output from the oscillation circuit 10 and input to the oscillation control circuit 20 is divided by the voltage dividing circuit 24 and then output to the determination circuit 30. On the other hand, when the impedance of the magnetic field detection element 21 is lower than a predetermined threshold value, the switching element 23 is turned off. In this case, the oscillation signal output from the oscillation circuit 10 and input to the oscillation control circuit 20 is output to the determination circuit 30 as it is without being divided by the voltage dividing circuit 24.

The voltage dividing circuit 24 is composed of two resistors R1 and R2 connected in series between the output terminal of the oscillation circuit 10 and the switching element 23. One end of the resistor R1 is connected to the output terminal of the oscillation circuit 10, and the other end is connected to one end of the resistor R2. Further, the other end of the resistor R2 is connected to the switching element 23. Then, an oscillation signal having an amplitude corresponding to the input amplitude is output from between the other end of the resistor R1 and one end of the resistor R2. Therefore, when the switching element 23 is turned on, the amplitude of the oscillating signal output from the voltage dividing circuit 24 is the amplitude of the oscillating signal output from the oscillating circuit 10, and the impedance of the resistor R1 of the voltage dividing circuit 24 and the resistance R2. It is attenuated by dividing the voltage by the ratio of the impedance of the resistor R2 to the sum of the impedances. On the other hand, when the switching element 23 is off, no current flows toward the resistor R2, and the oscillation signal output from the oscillation circuit 10 is not divided by the voltage divider circuit 24. Therefore, in this case, the amplitude of the oscillating signal from the oscillating circuit 10 does not decrease, and the oscillating signal is output as it is from the voltage dividing circuit 24.

The magnetic field detection element 21 may be configured so that the impedance decreases as the strength of the magnetic field due to the interaction between the detection object 100 and the oscillation coil 11 decreases. In this case, in the voltage dividing circuit 22, the magnetic field detection element 21 may be connected to the voltage source side of the resistor R0. In this case, as the impedance of the magnetic field detection element 21 decreases, the output voltage from the voltage dividing circuit 22 increases. Then, when the amount of decrease in the impedance of the magnetic field detection element 21 from the reference impedance becomes equal to or greater than a predetermined threshold value, the switching element 23 is turned on, and the amplitude of the oscillation signal from the oscillation circuit 10 is suppressed in the same manner as described above.

The determination circuit 30 determines whether or not the detection object 100 has been detected by comparing a signal value having a voltage corresponding to the amplitude of the oscillation signal with a predetermined threshold voltage. Therefore, the determination circuit 30 includes, for example, a detection circuit 31 connected in series from the oscillation control circuit 20 side, a discrimination circuit 32, and an output circuit 33.

The detection circuit 31 has, for example, a circuit for envelope detection of an oscillation signal input via an oscillation control circuit 20. The detection circuit 31 may include a full-wave rectifier circuit or a half-wave rectifier circuit that rectifies the input oscillation signal, and a smoothing circuit that smoothes the rectified oscillation signal. Then, the detection circuit 31 outputs a signal having a larger voltage as the amplitude of the oscillation signal input via the oscillation control circuit 20 is larger.

The discrimination circuit 32 compares the signal output from the detection circuit 31 with a predetermined threshold voltage, and outputs a signal having a voltage corresponding to the comparison result. Therefore, the discrimination circuit 32 has, for example, a comparator, and a signal output from the detection circuit 31 is input to one of the two input terminals of the comparator, and a threshold voltage is input to the other of the two input terminals. As a result, a signal having a voltage corresponding to the comparison result between the voltage of the signal output from the detection circuit 31 and the predetermined threshold voltage is output from the output terminal of the comparator. The discrimination circuit 32 may have a circuit having another configuration for comparing the voltage of the signal output from the detection circuit 31 with the predetermined threshold voltage.

The output circuit 33 has an interface circuit for outputting the signal output from the discrimination circuit 32 to another circuit, for example, the main control circuit of the device on which the proximity sensor 1 is mounted. Then, the output circuit 33 outputs a signal output from the discrimination circuit 32, that is, a detection signal representing the detection result of the detection target 100 by the proximity sensor 1.

FIG. 2 is a diagram showing an example of a change in the waveform of the oscillation signal from the oscillation circuit 10 and the waveform of the oscillation signal via the oscillation control circuit 20 according to the change in the distance between the detection object 100 and the proximity sensor 1. be. In FIG. 2, the horizontal axis represents time and the vertical axis represents voltage. The waveform 201 represents the waveform of the oscillation signal from the oscillation circuit 10, and the waveform 202 represents the waveform of the oscillation signal output from the oscillation control circuit 20. Further, the waveform 203 represents the waveform of the signal output from the detection circuit 31, and the waveform 204 represents the waveform of the signal when the oscillation signal from the oscillation circuit 10 is directly detected by the detection circuit 31 as a comparative example. .. Further, the waveform 205 represents the waveform of the detection signal output from the output circuit 33. When the voltage of the detection signal is V1, it means that the detection target object 100 has been detected, while when the voltage of the detection signal is V0, it means that the detection target object 100 has not been detected.

In FIG. 2, in the period P1, the detection object 100 gradually approaches the oscillation coil 11, and in the period P2, the oscillation control circuit 20 does not reduce the amplitude of the oscillation signal output from the oscillation circuit 10. It is assumed that the detection target object 100 exists at a position close to the oscillation coil 11 so that it can be detected, and the detection target object 100 gradually moves away from the oscillation coil 11 during the period P3. As shown in the waveform 201, the amplitude of the oscillation signal from the oscillation circuit 10 gradually decreases as the detection object 100 approaches the oscillation coil 11. Then, when the detection object 100 approaches the oscillation coil 11 to some extent or more as in the period P2, the oscillation circuit 10 does not oscillate. Further, the amplitude of the oscillation signal from the oscillation circuit 10 gradually increases as the detection object 100 moves away from the oscillation coil 11. Further, as shown in the waveform 202, when the detection object 100 approaches the oscillation coil 11 so that the amount of change in the impedance of the magnetic field detection element 21 with respect to the reference impedance becomes equal to or greater than a predetermined threshold value at time t1, the oscillation control circuit 20 The switching element 23 is turned on, and the amplitude of the output signal from the oscillation control circuit 20 becomes smaller than the amplitude of the oscillation signal from the oscillation circuit 10. This state continues until the detection target 100 moves away from the oscillation coil 11 so that the amount of change in the impedance of the magnetic field detection element 21 becomes smaller than a predetermined threshold value at time t2. Therefore, as shown in waveforms 203 to 205, the oscillation signal from the oscillation circuit 10 is directly detected during the period during which the voltage of the signal output from the detection circuit 31 is equal to or less than the threshold voltage Vsh used in the discrimination circuit 32. When this is done, the signal voltage becomes longer than the period during which the threshold voltage is Vsh or less. That is, it can be seen that the detectionable distance of the proximity sensor 1 becomes longer by providing the magnetic field detection element 21 and the oscillation control circuit 20 in the proximity sensor 1.

FIG. 3 is an external perspective view of the proximity sensor 1, and FIG. 4 is an exploded perspective view of the proximity sensor 1. FIG. 5 is a side view of the circuit board included in the proximity sensor 1. As shown in FIGS. 3 to 5, the proximity sensor 1 includes a case 101, a cover 102, a circuit board 103 on which each circuit shown in FIG. 1 is provided, and a ferrite core 104 formed of a ferrite material. Have. The ferrite core 104 may be omitted.

A cylindrical core portion 103a is provided on one end side of the circuit board 103 for winding the amorphous wire constituting the oscillation coil 11 and the magnetic field detection element 21, and the ferrite core 104 is inserted into the cylindrical core portion 103a. NS. Therefore, both the oscillation coil 11 and the magnetic field detection element 21 are wound around the ferrite core 104. Further, the main body 13, the oscillation control circuit 20, the determination circuit 30, and the like of the oscillation circuit 10 are provided on one surface of the circuit board 103. The case 101 and the cover 102 form a housing of the proximity sensor 1 that houses the circuit board 103 and the ferrite core 104 in the assembled state.

The magnetic field detection element 21 is arranged between the assumed position when the detection object 100 comes closest to the oscillation coil 11 and the oscillation coil 11. In the example shown in FIG. 5, the assumed position when the detection object 100 comes closest to the oscillation coil 11 is located above the surface 103b of the circuit board 103. Therefore, the oscillation coil 11 and the magnetic field detection element 21 are arranged side by side along the normal direction with respect to the surface 103b of the circuit board 103, that is, the axial direction of the core portion 103a, and the magnetic field detection element is more than the oscillation coil 11. 21 is provided at a position farther from the surface 103b of the circuit board 103. As a result, the magnetic field detection element 21 can detect a change in the magnetic field strength due to the interaction between the detection object 100 and the oscillation coil 11 in the normal direction of the surface 103b of the circuit board 103 and above the surface 103b. It becomes. Therefore, the detectable distance of the proximity sensor 1 in the normal direction of the surface 103b of the circuit board 103 and above the surface 103b is larger than the detectable distance of the proximity sensor 1 in other directions. In this way, the proximity sensor 1 can have directivity with respect to the detection direction.

The proximity sensor 1 according to this embodiment can be mounted on various devices. In particular, the proximity sensor 1 is suitably used in a device in which an object or mechanism that detects an object to be detected existing in a specific direction and causes a fluctuation of a magnetic field in another direction exists. For example, the proximity sensor 1 may be mounted on a gaming machine and used to detect a gaming ball passing through a flow path provided in the gaming machine.

FIG. 6A is an external perspective view of the flow path of the game ball, showing an example of the arrangement of the proximity sensors in the gaming machine having the proximity sensors. In this example, the game ball is an example of a detection object. FIG. 6B is a cross-sectional view of the flow path in the line seen from the arrows A and A'sides in FIG. 6A. In the example shown in FIGS. 6 (a) and 6 (b), the gaming machine is provided with two flow paths 601 and 602 so as to be adjacent to each other in a part thereof. Then, the two proximity sensors 1-1 and 1-2 according to the above embodiment are arranged between the flow path 601 and the flow path 602 in the portion where the flow path 601 and the flow path 602 are adjacent to each other, respectively. ..

The proximity sensor 1-1 is installed so that the detection range 621 of the proximity sensor 1-1 points toward the flow path 601 so that the game ball 611 flowing down in the flow path 601 can be detected. That is, the proximity sensors 1-1 are arranged so that the magnetic field detection element 21 and the oscillation coil 11 are arranged in this order from the side closest to the flow path 601. Therefore, the detection range 621 of the proximity sensor 1-1 overlaps with the flow path 601 but does not overlap with the flow path 602. Therefore, the proximity sensor 1-1 detects the game ball 611 when the game ball 611 flowing down in the flow path 601 enters the detection range 621, while not detecting the game ball 612 flowing down in the flow path 602. ..

Similarly, the proximity sensor 1-2 is installed so that the detection range 622 of the proximity sensor 1-2 points toward the flow path 602 so that the game ball 612 flowing down in the flow path 602 can be detected. That is, the proximity sensors 1-2 are arranged so that the magnetic field detection element 21 and the oscillation coil 11 are arranged in this order from the side closest to the flow path 602. Therefore, the detection range 622 of the proximity sensor 1-2 overlaps with the flow path 602, but does not overlap with the flow path 601. Therefore, the proximity sensor 1-2 detects the game ball 612 when the game ball 612 flowing down in the flow path 602 enters the detection range 622, while it does not detect the game ball 611 flowing down in the flow path 601. .. As described above, since the proximity sensors 1-1 and 1-2 have directivity, the game ball flowing down the flow path to be detected without erroneously detecting the game ball flowing down the flow path other than the detection target. Can be detected.
Even if there is a mechanism that causes fluctuations in the magnetic field on the side opposite to the flow path with the proximity sensor in between, the proximity sensor 1 is installed so that the magnetic field detection element 21 and the oscillation coil 11 are arranged in this order from the flow path side. By doing so, the proximity sensor 1 can accurately detect the game ball flowing down the flow path without erroneously detecting the game ball by the operation of such a mechanism.

As described above, this proximity sensor has a magnetic field due to the interaction between the detection object and the oscillation coil, separately from the oscillation circuit that outputs an oscillation signal having an amplitude that attenuates as the detection object approaches the oscillation coil. It has a magnetic field detection element whose impedance changes according to the strength of the coil. Then, this proximity sensor suppresses the amplitude of the oscillation signal output from the oscillation circuit when the amount of change in the impedance of the magnetic field detection element with respect to the reference impedance becomes equal to or greater than a predetermined threshold value due to the approach of the detection object. As a result, the proximity sensor can increase the distance between the oscillation coil and the detection object, that is, the detectable distance, at which the signal value corresponding to the amplitude of the oscillation signal is equal to or less than the threshold value. Further, since this proximity sensor determines the presence / absence of the detection target object based on the oscillation signal from the oscillation circuit having a relatively good signal-to-noise ratio, the detection target object can be accurately detected even if the detectable distance is increased. Can be detected. Further, this proximity sensor can have directivity in the detection direction depending on the arrangement direction of the oscillation coil and the magnetic field detection element.

According to the modification, the oscillation control circuit of the proximity sensor may have a constant current source instead of the voltage dividing circuit 24.

FIG. 7 is a circuit configuration diagram of the proximity sensor 2 according to a modified example. The proximity sensor 2 according to this modification has an oscillation circuit 10, an oscillation control circuit 40, and a determination circuit 30. In the proximity sensor 2 according to this modification, the oscillation control circuit 40 divides the voltage of the constant current source 25 connected between the oscillation circuit 10 and the switching element 23 as compared with the proximity sensor 1 shown in FIG. The difference is that it is provided in place of the circuit 24 and that the oscillation signal output from the oscillation circuit 10 is directly input to the determination circuit 30. Therefore, this difference and related parts will be described below. For details of the other components of the proximity sensor 2, refer to the description of the corresponding components of the proximity sensor 1.

The constant current source 25 is a circuit that is connected between the oscillating circuit 10 and the switching element 23, and is configured to allow a constant current to flow from the oscillating circuit 10 to the ground when the switching element 23 is turned on. The ground is an example of a predetermined circuit other than the oscillation coil 11. The constant current source 25 may be connected to another circuit (not shown) different from the oscillation coil 11 via the switching element 23. That is, when the amount of change in the impedance of the magnetic field detection element 21 with respect to the reference impedance as the detection object 100 approaches the oscillation coil 11, the switching element 23 is turned on. Then, when the switching element 23 is turned on, a constant current flows out from the oscillation circuit 10 via the constant current source 25. As a result, the amplitude of the oscillation signal output from the oscillation circuit 10 becomes small. On the other hand, when the amount of change in impedance of the magnetic field detection element 21 is smaller than a predetermined threshold value, the switching element 23 remains off and the outflow of current from the oscillation circuit 10 is stopped. Therefore, the amplitude of the oscillation signal output from the oscillation circuit 10 does not decrease, and the oscillation signal is output to the determination circuit 30. Therefore, the proximity sensor 2 according to this modification also has the same effect as the proximity sensor 1 according to the above embodiment.

According to another modification, the oscillation control circuit may be connected between the oscillation coil 11 and the resonance capacitor 12 of the oscillation circuit 10 and the oscillation circuit main body 13.

FIG. 8 is a circuit configuration diagram of the proximity sensor 3 according to another modification. The proximity sensor 3 according to this modification has an oscillation circuit 10, an oscillation control circuit 50, and a determination circuit 30. In the proximity sensor 3 according to this modification, the connection position and configuration of the oscillation control circuit 50 and the oscillation signal output from the oscillation circuit 10 are directly input to the determination circuit 30 as compared with the proximity sensor 1 shown in FIG. It differs in that it is done. Therefore, this difference and related parts will be described below. For details of the other components of the proximity sensor 3, refer to the description of the corresponding components of the proximity sensor 1.

The oscillation control circuit 50 has a magnetic field detection element 21 and a resistor R0 connected in parallel to each other between the oscillation coil 11 and the resonance capacitor 12 of the oscillation circuit 10 and the oscillation circuit main body 13. The resistor R0 may be a variable resistor for adjusting the detectable distance. Then, the current from the oscillation circuit main body 13 is supplied to the oscillation coil 11 and the resonance capacitor 12 via the oscillation control circuit 50. Therefore, as the detection object 100 approaches the oscillation coil 11 and the strength of the magnetic field due to the interaction between the detection object 100 and the oscillation coil 11 decreases, the impedance of the magnetic field detection element 21 increases, and as a result, oscillation occurs. The amount of current supplied to the coil 11 and the resonance capacitor 12 is smaller than that without the oscillation control circuit 50. Therefore, the amplitude of the oscillation signal output from the oscillation circuit 10 is also lower than that without the oscillation control circuit 50. On the other hand, as the detection object 100 moves away from the oscillation coil 11, the impedance of the magnetic field detection element 21 decreases, so that the amount of current supplied to the oscillation coil 11 and the resonance capacitor 12 increases. Therefore, the amplitude of the oscillation signal output from the oscillation circuit 10 also increases. Therefore, the proximity sensor 3 according to this modification also has the same effect as the proximity sensor 1 according to the above embodiment. Further, since the proximity sensor 3 according to this modification can simplify the configuration of the oscillation control circuit 50, the configuration of the proximity sensor 3 itself can also be simplified.

The magnetic field detection element 21 may be configured such that the impedance decreases as the strength of the magnetic field due to the interaction between the detection object 100 and the oscillation coil 11 decreases. In this case, the magnetic field detection element 21 of the oscillation control circuit 50 may be connected in parallel with the oscillation coil 11 to the main body of the oscillation circuit 13. By connecting the magnetic field detection element 21 in this way, as the detection object 100 approaches the oscillation coil 11, the strength of the magnetic field due to the interaction between the detection object 100 and the oscillation coil 11 decreases, and the oscillation circuit The current flowing from the main body 13 to the magnetic field detection element 21 increases. Therefore, the amount of current supplied to the oscillation coil 11 and the resonance capacitor 12 is reduced, and the amplitude of the oscillation signal output from the oscillation circuit 10 is lower than the amplitude of the oscillation signal when the oscillation control circuit 50 is not provided. .. Therefore, also in this case, the proximity sensor 3 has the same effect as the proximity sensor 1 according to the above embodiment.

Proximity sensors according to these modifications may also be mounted on the circuit board 103 shown in FIG. 4 and housed in the case 101 and the cover 102 shown in FIGS. 3 and 4. Further, as shown in FIGS. 6A and 6B, the proximity sensor according to these modifications can also be used to detect a gaming ball flowing down the flow path in the gaming machine.

According to still another modification, the oscillation coil itself may be formed by a magnetic impedance element.

FIG. 9 is a circuit configuration diagram of the proximity sensor 4 according to still another modification. Further, FIG. 10 is an equivalent circuit diagram of the oscillation circuit 10 and the detection object 100. The proximity sensor 4 according to this modification has an oscillation circuit 10 and a determination circuit 30. Compared with the proximity sensor 1 shown in FIG. 1, the proximity sensor 4 according to this modification does not have the oscillation control circuit 20, but the oscillation coil 14 of the oscillation circuit 10 is formed by the magnetic impedance element. Is different. Therefore, this difference and related parts will be described below. For details of the other components of the proximity sensor 4, refer to the description of the corresponding components of the proximity sensor 1.

ここで、r1は、発振コイル１４自身の固有の抵抗値であり、Δr1は、検知対象物１００と発振コイル１４の相互作用による磁界の強さの変化に応じた、発振コイル１４を形成する磁気インピーダンス素子の抵抗値成分の変化量を表す。また、r2は、検知対象物１００の抵抗値を表す。さらに、L1は、発振コイル１４自身のインダクタンスを表し、ΔL1は、検知対象物１００と発振コイル１４の相互作用による磁界の強さの変化に応じた、発振コイル１４を形成する磁気インピーダンス素子のインダクタンス成分の変化量を表す。さらに、L2は、検知対象物１００のインダクタンスを表す。さらにまた、Mは、発振コイル１４と検知対象物１００の相互インダクタンスを表す。そしてωは、発振回路１０の発振信号の角周波数であり、発振回路１０の発振周波数をfとすれば、角周波数ω=2πfである。 The oscillation coil 14 is formed by a magnetic impedance element such as an amorphous wire. In this case, the impedance Z of the oscillating coil 14 when the detection object 100 interacts with the magnetic field of the oscillating coil 14 is expressed by the following equation.

Here, r1 is the unique resistance value of the oscillating coil 14 itself, and Δr1 is the magnetism that forms the oscillating coil 14 according to the change in the strength of the magnetic field due to the interaction between the detection object 100 and the oscillating coil 14. Represents the amount of change in the resistance value component of the impedance element. Further, r2 represents the resistance value of the detection object 100. Further, L1 represents the inductance of the oscillating coil 14 itself, and ΔL1 is the inductance of the magnetic impedance element forming the oscillating coil 14 according to the change in the strength of the magnetic field due to the interaction between the detection object 100 and the oscillating coil 14. Represents the amount of change in the components. Further, L2 represents the inductance of the detection object 100. Furthermore, M represents the mutual inductance of the oscillating coil 14 and the detection object 100. And ω is the angular frequency of the oscillating signal of the oscillating circuit 10, and if the oscillating frequency of the oscillating circuit 10 is f, the angular frequency ω = 2πf.

As is clear from the equation (1), as the detection object 100 approaches the oscillation coil 14, not only the mutual inductance M due to the eddy current loss in the detection object 100 increases, but also the magnetic impedance element forming the oscillation coil 14 increases. The impedance Z of the oscillating coil 14 increases as the amount of change Δr1 of the resistance value component increases. Then, as the impedance Z increases, the amplitude of the oscillation signal output from the oscillation circuit 10 is attenuated. Therefore, as the detection object 100 approaches the oscillating coil 14, the amplitude of the oscillating signal output from the oscillating circuit 10 becomes lower than the amplitude of the oscillating signal when the oscillating coil 14 is not formed by the magnetic impedance element. Therefore, similarly to the above-described embodiment and each modification, the proximity sensor 4 according to this modification can increase the detectable distance. Further, the proximity sensor 4 determines the presence / absence of the detection target 100 based on the oscillation signal from the oscillation circuit having a relatively good signal-to-noise ratio, as in the above embodiment or each modification, so that detection is possible. Even if the distance is increased, the detection target 100 can be detected with high accuracy. Further, unlike the above-described embodiment and each modification, in the proximity sensor 4, since the oscillation coil itself is formed by the magnetic impedance element, it is possible to suppress that the detection direction has directivity. Furthermore, since the oscillation coil itself is formed of a magnetic impedance element, the circuit configuration of the proximity sensor 4 can be simplified, and as a result, the proximity sensor 4 can be miniaturized.

FIG. 11 is an external perspective view of the proximity sensor 4, and FIG. 12 is an exploded perspective view of the proximity sensor 4. As shown in FIGS. 11 and 12, the proximity sensor 4 has a case 201, a cover 202, and a circuit board 203 on which each of the circuits shown in FIG. 9 is provided.

A columnar spool 203b protruding along the normal direction of the surface 203a of the circuit board 203 is provided on one end side of the circuit board 203 in order to wind the amorphous wire forming the oscillation coil 14. The spool 203b may be made of a ferrite material. Further, the main body of the oscillation circuit 10 and the determination circuit 30 are provided on one surface of the circuit board 203. The case 201 and the cover 202 form a housing of the proximity sensor 4 that houses the circuit board 203 in the assembled state.

As described above, since the oscillation coil 14 itself is formed by the magnetic impedance element, the directivity of the proximity sensor 4 in the detection direction is suppressed. Therefore, the proximity sensor 4 can detect an object to be detected approaching from any side of the winding shaft of the oscillation coil 14, that is, from either the front surface side or the back surface side of the circuit board 203. Therefore, the proximity sensor 4 is suitably used, for example, in a device in which a detection object may approach not only the front surface side of the circuit board 203 but also the back surface side. For example, when it is sufficient to detect a gaming ball flowing down any of the two flow paths of the gaming machine shown in FIGS. 6 (a) and 6 (b) without distinction, the two proximity sensors 1- One proximity sensor 4 may be used instead of 1, 1-2.
The proximity sensor 4 may also be mounted on the housing and the circuit board shown in FIGS. 3 and 4 in the same manner as the proximity sensor according to the above embodiment or each modification.

As described above, a person skilled in the art can make various changes within the scope of the present invention according to the embodiment.

1, 1-1, 1-2, 2, 3, 4 Proximity sensor 10 Oscillation circuit 11, 14 Oscillation coil 12 Resonance capacitor 13 Oscillation circuit body 20, 40, 50 Oscillation control circuit 21 Magnetic field detection element 22, 24 Pressure division circuit 23 Switching element 25 Constant current source 30 Judgment circuit 31 Oscillator circuit 32 Discrimination circuit 33 Output circuit 100 Detection target 101, 201 Case 102, 202 Cover 103, 203 Circuit board 104 Ferrite core 601, 602 Flow path

Claims (6)

An oscillating circuit having an oscillating coil and outputting an oscillating signal having an amplitude that attenuates as a detection object formed of metal approaches the oscillating coil.
It has a magnetic field detection element whose impedance changes according to a change in the strength of the magnetic field due to the interaction between the detection object and the oscillation coil, and the amplitude of the oscillation signal according to the amount of change in the impedance of the magnetic field detection element. Oscillation control circuit that reduces
A determination circuit that determines whether or not the detection object has been detected by comparing a signal value corresponding to the amplitude of the oscillation signal output from the oscillation control circuit with a predetermined threshold value.
Proximity sensor with. The oscillation control circuit is
A voltage dividing circuit connected between the oscillation circuit and the determination circuit and capable of reducing the amplitude of the oscillation signal by dividing the oscillation signal.
When the amount of change in impedance of the magnetic field detection element is equal to or greater than a predetermined threshold value, the voltage dividing circuit is made to divide the oscillation signal, and when the amount of change in impedance of the magnetic field detecting element is less than the predetermined threshold value, the voltage dividing circuit is used. The proximity sensor according to claim 1, further comprising a switching element that does not divide the oscillation signal. The oscillation control circuit reduces the amplitude of the oscillation signal by passing a constant amount of current from the oscillation circuit to a predetermined circuit other than the oscillation coil when the amount of change in the impedance of the magnetic field detection element exceeds a predetermined threshold value. The present invention claims that when the amount of change in the impedance of the magnetic field detection element becomes less than the predetermined threshold value, the outflow of current from the oscillation circuit to the predetermined circuit is stopped to suppress a decrease in the amplitude of the oscillation signal. The proximity sensor according to 1. The oscillating circuit further includes an oscillating circuit body that supplies a current to the oscillating coil.
The impedance of the magnetic field detection element increases as the strength of the magnetic field decreases due to the interaction between the detection object and the oscillation coil, and the magnetic field detection element is connected between the oscillation coil and the oscillation circuit main body. The proximity sensor according to claim 1. The oscillating circuit further includes an oscillating circuit body that supplies a current to the oscillating coil.
The impedance of the magnetic field detection element decreases as the strength of the magnetic field decreases due to the interaction between the detection object and the oscillation coil, and the magnetic field detection element is connected to the oscillation circuit main body in parallel with the oscillation coil. , The proximity sensor according to claim 1. It has an oscillating coil formed by a magnetic impedance element, and as the detection object formed of metal approaches the oscillating coil, the amount of change in impedance by the magnetic impedance element and the mutual between the detection object and the oscillating coil. An oscillator circuit that outputs an oscillation signal with an amplitude that decays according to the amount of change in the strength of the magnetic field due to the action,
A determination circuit that determines whether or not the detection target is detected by comparing a signal value corresponding to the amplitude of the oscillation signal from the oscillation circuit with a predetermined threshold value.
Proximity sensor with.

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