JP2009033306A - Operation distance adjusting method of proximity sensor, and proximity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily adjust an operation distance to an operation distance adjustment point. <P>SOLUTION: In a proximity sensor which includes an oscillation circuit unit 3 varying in oscillation amplitude level with a proximity distance of a detection body 11 and a detecting circuit unit 7 outputting an operation signal on detecting the oscillation amplitude level varying to reach a detection threshold as the detection body approaches, and determines as an operation distance the distance from the detection body when the operation signal is output, the operation distance is adjusted by bringing the oscillation output of the oscillation circuit unit under feedback control so that the oscillation amplitude level reaches the detection threshold at an operation distance adjustment point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for adjusting the operating distance in a high-frequency oscillation / amplitude detecting proximity sensor in which there is a difference between an operating distance in which the proximity sensor operates close to a detection object and a return distance in which the proximity sensor returns. It relates to the proximity sensor.

  The proximity sensor of the high-frequency oscillation / amplitude detection type oscillates at a constant frequency and detects a change in the amplitude of oscillation by the approach of a detection object such as a metal body. This proximity sensor has an oscillation circuit section that oscillates at a high frequency. When a detection object made of a metal body or a magnetic body approaches the oscillation coil in the oscillation circuit section, an eddy current loss occurs due to electromagnetic induction and the oscillation coil becomes effective. It utilizes the fact that the oscillation amplitude of the oscillation circuit changes as the impedance, which is the resistance value, changes, and the oscillation amplitude of the oscillation circuit changes dramatically according to the proximity state of the detection object. Alternatively, the presence / absence of a detection object can be determined based on a change in oscillation amplitude caused by stopping oscillation (see Patent Document 1). In this case, the detection output obtained by converting the output of the oscillation circuit unit into a direct current decreases as the detection object approaches, and increases as the detection object moves away.

  In such a high-frequency oscillation / amplitude detection type proximity sensor, when the detection object approaches and the detection output becomes small and coincides with the detection threshold value, a signal indicating the presence of the detection object is generated, and the detection object is separated and the detection output is output. When it becomes larger, a signal indicating no detected object is generated. Hysteresis is provided between the signal with the detection object and the signal without the detection object to turn the signal on and off. As a result of providing a level difference in the detection output for generating the signal with the detection object and the detection output without the detection object to prevent malfunction by chattering, there is a difference between the operation distance and the return distance ( Patent Document 2).

  In the above configuration, the oscillation amplitude of the oscillation circuit unit corresponding to the same operating distance is slightly different for each product. Therefore, even if the detection threshold is set, the operating distance may be slightly different for each product.

  In general, therefore, the operating distance is accurately adjusted by adjusting the oscillation amplitude of the oscillation circuit section before shipping the product.

  As a method of adjusting the operating distance, conventionally, the resistor for limiting the oscillation current flowing in the oscillation circuit section is changed or changed in the manufacturing process, or the resistance value is adjusted by resistance value laser trimming. Yes.

However, in the former, workability is very bad, for example, it is necessary to measure the working distance again after repeating the change of the resistor several times, and in the latter, an expensive laser trimming device is necessary. In addition, the laser trimming work efficiency is not necessarily high.
JP 2007-141762 A JP-A-10-256894

  Therefore, the problem to be solved by the present invention is to make it possible to easily adjust the operating distance that moves close to the detection object to the operating distance adjustment point.

  The method according to the present invention operates by detecting an oscillation circuit unit in which the oscillation amplitude level changes according to the approach distance of the detection object, and that the oscillation amplitude level changes with the detection object approaching until it matches the detection threshold. A detection circuit unit that outputs a signal, and for a proximity sensor whose operating distance is the distance from the detected object at the time when the operating signal is output, the oscillation amplitude level is captured as data in the operating distance adjustment mode. At the same time, the oscillation operation of the oscillation circuit unit is feedback-controlled so that the oscillation amplitude level indicated by the captured data coincides with the detection threshold at a predetermined operating distance.

  According to the present invention, the oscillation amplitude level is captured as data, and the oscillation distance of the oscillation circuit unit is feedback-controlled so that the oscillation amplitude level indicated by the captured data coincides with the detection threshold at a predetermined operation distance. Therefore, to adjust the operating distance, the operating distance can be adjusted without changing the resistance value of the resistor that limits the operating current of the oscillation circuit. Can be adjusted to a point. For example, before the factory shipment, the detection distance of the detection circuit unit can be corrected to correspond to the operation distance adjustment point, and the operation distance can be adjusted to the operation distance adjustment point. In addition, laser trimming of resistors by an expensive laser trimming apparatus is not necessary.

  One of the preferred embodiments stores the oscillation operation of the oscillation circuit unit when the oscillation amplitude level matches the detection threshold at a predetermined operating distance by the feedback control, and stores the oscillation circuit unit in the operation mode. Oscillation is controlled by oscillation operation.

  In this aspect, once the oscillation operation of the oscillation circuit unit is feedback-controlled so that the proximity of the detection object can be detected at a predetermined operating distance, the oscillation operation of this oscillation circuit unit is stored. If the operating distance is adjusted once before shipment, the subsequent adjusting of the operating distance becomes unnecessary, and a proximity sensor with an accurate operating distance can be provided to the user.

  According to the present invention, the operating distance can be easily adjusted without having to replace the resistor of the oscillation circuit section or perform laser trimming.

  Hereinafter, a method for adjusting an operating distance of a high-frequency oscillation / amplitude detection type proximity sensor (hereinafter referred to as a proximity sensor) according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a schematic block configuration of a proximity sensor to which the embodiment is applied.

  The proximity sensor 1 includes an oscillation circuit unit 3 including an oscillation coil 3 a and a detection circuit 3 b, a rectification circuit unit 5 that rectifies the oscillation output of the oscillation circuit unit 3 and converts it into a direct current, and an oscillation amplitude that accompanies the detection object 11. A detection circuit unit 7 that detects that the level OUT has changed until it matches the detection threshold value Vst1 and outputs an operation signal, and a detection signal that indicates the presence or absence of a detection object is generated according to the output of the detection circuit unit 7. And an output circuit unit 9.

  In the embodiment, an operating distance adjustment circuit unit 13 is provided that feedback-controls the oscillation circuit unit 3 with a feedback control signal so that the oscillation amplitude level OUT coincides with the detection threshold value Vst1 at a predetermined operating distance. . In this case, the operating distance adjustment circuit unit 13 performs the above feedback control by the direct current output from the rectification circuit unit 5, but will be described with the oscillation amplitude level OUT for convenience of explanation. In addition, since the operating distance adjustment circuit unit 13 is configured by a microcomputer, the operation distance adjustment circuit unit 13 includes an AD conversion value of a DC output of the rectification circuit unit 5 and a detection threshold value Vst1 that is a digital value. Processing is performed, and the processing result is DA-converted and provided to the oscillation circuit unit 3 as a feedback control signal.

  With the above configuration, when the detection object 11 made of a metal body, a magnetic body, or the like approaches the oscillation coil, the oscillation circuit unit 3 causes an eddy current loss due to the electromagnetic induction action, and the impedance that is the effective resistance value of the oscillation coil 3a changes. As a result, the amplitude (oscillation amplitude) of the oscillation output of the oscillation circuit unit 3 changes, and the oscillation amplitude of the oscillation circuit unit 3 changes according to the proximity state of the detection object 11 to oscillate or stop oscillation. Therefore, the detection circuit 3b can detect the presence or absence of the detection object. The rectifier circuit unit 5 converts the oscillation output of the oscillation circuit unit 3 into a direct current corresponding to the magnitude of the oscillation amplitude and outputs it as an oscillation amplitude level OUT. When the detection object 11 approaches, the oscillation amplitude level OUT data decreases. As the detection object 11 moves away, the oscillation amplitude level OUT increases.

  The detection circuit unit 7 is a circuit that outputs a high-level operation signal H as the presence of the detection object 11 when the oscillation amplitude level OUT reaches the detection threshold Vst1 in accordance with the approach of the detection object 11. The detection circuit unit 7 outputs a low level signal L when the detection object 11 is not detected.

  As described above, the operating distance adjustment circuit unit 13 is constituted by a microcomputer, and as shown in FIG. 2, a detection threshold value storage means 131 that stores a detection threshold value in terms of operating distance in a rewritable manner, and a predetermined operating distance. Operating distance adjustment point storage means 132 that stores the corresponding operating distance adjustment point Von, and control means 133 that controls the oscillation amplitude level OUT so that the oscillation amplitude level OUT coincides with the detection threshold Vst1 at a predetermined operating distance. And having. The control means 133 is constituted by a CPU. 134 is an AD conversion interface that AD converts the detection output OUT from the rectifier circuit unit 5, 135 is a DA conversion interface that DA converts a feedback signal to the oscillation circuit unit 3, and 136 is a program in which a control program of the control unit 133 is stored. The memory 137 has data for setting the detection threshold and the operating distance adjustment point Von in the storage means 131 and 132, the operating distance adjusting circuit unit 13 is set to the operating distance adjusting mode, the operating distance adjusting mode is stopped, It is an external interface for taking in various mode control signals for switching to the operation mode. The two storage means 131 and 132 are structurally two, but can be constituted by one data memory, and work memory, which is a work area of the control means 133 composed of a CPU, and the like. Illustration is omitted.

  The operation by the control means 133 will be described.

  When a mode control signal for setting the proximity sensor 1 to the operation distance adjustment mode is input to the external interface 137, the control unit 133 sets the proximity sensor 1 to the operation distance adjustment mode. On the other hand, the detection object 11 is arranged opposite to the proximity sensor 1 with a predetermined operation distance corresponding to the operation distance adjustment point Von. In this state, the control means 133 reads the operating distance adjustment control program stored in the program memory 136 and performs the following control. First, the detection threshold value Vst1 data is read from the detection threshold value storage means 131, and the operating distance adjustment point Von data is read from the operating distance adjustment point storage means, and the oscillation amplitude level OUT data is fetched from the rectifier circuit unit 5 via the AD conversion interface 134. . The control means 133 measures the oscillation amplitude level OUT at the operating distance adjustment point Von, and feeds back a feedback control signal to the oscillation circuit unit 3 via the DA conversion interface 135 so that the oscillation amplitude level OUT coincides with the detection threshold value Vst1. To do. The oscillation circuit unit 3 performs an oscillation operation in response to the feedback control signal, thereby matching the oscillation amplitude level OUT with the detection threshold value Vst1. And the control means 133 memorize | stores and preserve | saves the conditions of the oscillation operation | movement of the oscillation circuit part 3 at this time in the appropriate memory not shown.

  Next, when a mode control signal for setting the proximity sensor 1 to the normal operation mode is input to the external interface 137, the control unit 133 sets the proximity sensor 1 to the normal operation mode. In the normal operation mode, the control unit 133 controls the oscillation operation of the oscillation circuit unit 3 under the condition of the oscillation operation of the stored oscillation circuit unit 3, so that the detection circuit unit 7 is not connected to the output circuit unit 9. At the time of detection Voff, a low level signal L indicating that the detection object 11 is not detected, and a high level signal H can be output when the detection object 11 is close to a predetermined operating distance.

  The above operation will be described with reference to FIGS. FIG. 3 shows before adjustment of the operating distance, and FIG. 4 shows after adjustment of the operating distance. Before adjusting the operating distance, the detection object 11 approaches the proximity sensor 1 in the direction of the arrow as shown in FIG. 3A, and the oscillation circuit unit 3 at the approach position A as shown in FIG. When the oscillation amplitude level becomes OUTA, the oscillation amplitude level OUTA coincides with the detection threshold value Vst1 as shown in FIG. 3C. As a result, the detection circuit unit 7 operates and outputs an operation signal. In this case, the predetermined operating distance is the approach position B in FIG. 3A, the oscillation amplitude level corresponding to the approach position B is OUTB in FIG. 3B, and the corresponding operation distance adjustment is performed. The point is Von in FIG. That is, the oscillation amplitude level OUTB of the oscillation circuit unit at the approach position B that is a predetermined operating distance is smaller than the oscillation amplitude level OUTA at the approach position A, and the proximity sensor 1 is not adjusted to the predetermined operating distance.

  After adjusting the operating distance, the detection object 11 approaches the proximity sensor 1 in the direction of the arrow as shown in FIG. 4A, and the oscillation amplitude level OUTA ′ of the oscillation circuit unit 3 at the approach position A ′ is as shown in FIG. Since it is larger than the detection threshold value Vst1 corresponding to a predetermined operating distance as shown in (b), the detection circuit unit 7 does not operate. Then, the detection object 11 further approaches the proximity sensor 1 in the direction of the arrow, and the oscillation amplitude level OUTB ′ of the oscillation circuit unit 3 at the approach position B ′ corresponding to a predetermined operating distance is shown in FIG. In this manner, the detection circuit unit 7 operates to output an operation signal until it becomes smaller than the detection threshold value Vst1. In FIG. 4C, the detection threshold value Vst1 and the operating distance adjustment point Von determined corresponding to the predetermined operating distance coincide with each other, and the proximity sensor 1 is adjusted to the predetermined operating distance.

  The adjustment of the oscillation amplitude level of the oscillation circuit unit 3 by the operating distance adjustment circuit unit 13 is not particularly illustrated, but, for example, a configuration in which the oscillation circuit unit 3 is connected to a collector of an oscillation transistor and a parallel resonance circuit of a coil and a capacitor is connected. In this case, the power supply voltage can be controlled by feedback control, or the base current of the oscillation transistor can be controlled by feedback control.

  As described above, in the embodiment, the oscillation distance level OUT is taken into the operating distance adjustment circuit unit 13 as data, and the oscillation circuit so that the oscillation amplitude level OUT indicated by the fetched data coincides with the detection threshold at a predetermined operating distance. Since the operation distance is adjusted to a predetermined operation distance by feedback control of the oscillation operation of the unit 3, the operation distance is automatically adjusted without the need to adjust the resistor in the oscillation circuit unit 3. Can do.

FIG. 1 is a diagram showing a schematic block configuration of a proximity sensor to which an operating distance adjusting method according to an embodiment of the present invention is applied. FIG. 2 is a diagram showing a block circuit configuration when the detection circuit unit of FIG. 1 is configured by a microcomputer. FIG. 3 shows before adjustment of the operating distance, FIG. 3 (a) shows the positional relationship between the detected object and the proximity sensor, FIG. 3 (b) shows the oscillation amplitude waveforms at the approach positions A and B, and FIG. It is a figure which shows the relationship between detection threshold value Vst1 and the operating distance adjustment point Von. FIG. 4 shows the state after adjustment of the operating distance, FIG. 4 (a) shows the positional relationship between the detection object and the proximity sensor, FIG. 4 (b) shows the oscillation amplitude waveforms at the approach positions A and B, and FIG. It is a figure which shows the relationship between detection threshold value Vst1 and the operating distance adjustment point Von.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Proximity sensor 3 Oscillation circuit part 7 Detection circuit part 13 Operating distance adjustment circuit part

Claims (5)

An oscillation circuit unit whose oscillation amplitude level changes according to the approach distance of the detection object, and a detection circuit that detects that the oscillation amplitude level has changed until the detection object approaches the detection threshold and outputs an operation signal A proximity sensor having a distance from the detection object at the time when the operation signal is output as an operation distance,
In the operating distance adjustment mode, the oscillation amplitude level is captured as data, and the oscillation operation of the oscillation circuit unit is feedback-controlled so that the oscillation amplitude level indicated by the captured data matches the detection threshold at a predetermined operating distance. A method for adjusting an operating distance of a proximity sensor.   Storing the oscillation operation of the oscillation circuit unit when the oscillation amplitude level coincides with the detection threshold at a predetermined operation distance by the feedback control, and controlling the oscillation by the stored oscillation operation in the operation mode; The method according to claim 1. An oscillation circuit unit whose oscillation amplitude level changes according to the approach distance of the detection object, and a detection circuit that detects that the oscillation amplitude level has changed until the detection object approaches the detection threshold and outputs an operation signal And a proximity sensor whose operation distance is the distance from the detection object at the time when the operation signal is output,
In the operating distance adjustment mode, the oscillation amplitude level is captured as data, and the oscillation distance of the oscillation circuit unit is feedback controlled so that the oscillation amplitude level indicated by the acquired data matches the detection threshold at a predetermined operating distance. A proximity sensor characterized by comprising:   The operating distance adjustment circuit stores the oscillation operation of the oscillation circuit unit when the oscillation amplitude level matches the detection threshold at the predetermined operating distance by the feedback control, and stores the oscillation circuit unit in the operation mode. 4. The proximity sensor according to claim 3, wherein oscillation control is performed by an oscillation operation.   5. The proximity sensor according to claim 3, wherein the operating distance adjusting circuit is configured by a microcomputer that operates according to the program for feedback control.

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