JP2009033387A - 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: A proximity sensor 1 includes an oscillation circuit unit 3 varying in oscillation amplitude level as a detection body 11 approaches, a rectifying circuit unit 5 which converts the output of the oscillation circuit unit 3 into a DC current, and a detecting circuit unit 7 outputting a signal indicative of presence of the detection body 11 when the output of the rectifying circuit unit 5 matches a detection threshold. The detection threshold and operation distance operation point Von are stored in storage means 71 and 72, and if the operation distance when the proximity sensor 1 approaches the detection body 11 and operates with the detection threshold does not match the operation distance adjustment point Von, the detection threshold is corrected into Vs2 so that the they match each other, and then the corrected detection threshold is rewritten and stored in the storage means. <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 detection type proximity sensor having a difference between an operating distance in which the proximity sensor moves close to a detection object and a return distance in which the detection sensor returns to a detected object, and the method thereof It relates to a 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 operation distance is the distance from the detection object at the time when the operation signal is output, the detection distance in the detection circuit unit is corrected to correct the operation distance. It is characterized by adjusting.

  According to the present invention, the operating distance is adjusted by correcting the detection threshold. Therefore, in order to adjust the operating distance, it is necessary to change the resistance value of the resistor that limits the operating current of the oscillation circuit unit as in the past. The operating distance can be adjusted to the operating distance adjustment point. For example, the operating distance can be adjusted by correcting the detection threshold value of the detection circuit unit so as to correspond to a predetermined operating distance before shipment from the factory. Laser trimming of the resistor by the trimming device becomes unnecessary.

  One of the preferred embodiments stores the detection threshold value in the storage means, and when the operating distance when moving close to the detection object and operating at the detection threshold value does not match the predetermined operating distance, the detection threshold value is set to the predetermined value. The operating distance is adjusted by making correction so as to coincide with the operating distance adjustment point for adjusting to the operating distance and rewriting and storing the corrected detection threshold in the storage means.

  In this aspect, since the operating distance adjustment point is set in advance, when the detection threshold value is corrected, it can be corrected so as to coincide with this operating distance adjustment point, and the correction becomes easy. In addition, when the detection threshold value is stored in the storage unit, the detection threshold value can be rewritten and stored in the storage unit. Therefore, when the operating distance is shifted, the detection threshold value is corrected again. It is convenient for maintenance because it can be adjusted to a predetermined operating distance.

  According to the present invention, the operating distance can be easily adjusted to the operating distance adjustment point 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, a rectification circuit unit 5 that rectifies the oscillation output of the oscillation circuit unit 3 to convert it into a direct current, and a detection circuit unit 7 that detects the output of the rectification circuit unit 5. And an output circuit unit 9 for generating a detection signal indicating the presence or absence of a detection object in accordance with the output of the detection circuit unit 7.

  When the detection object 11 made of a metal body, a magnetic body, or the like approaches the oscillation coil, the oscillation circuit section 3 causes an eddy current loss due to electromagnetic induction action, and the impedance, which is an effective resistance value of the oscillation coil, changes. The amplitude (oscillation amplitude) level of the oscillation output of the unit 3 is changed, and the oscillation amplitude level of the oscillation circuit unit 3 is changed according to the proximity state of the detection object 11 to oscillate or stop oscillating. The presence / absence of the presence or absence can be detected.

  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 level and outputs it as a detection output. When the detection object 11 approaches and the oscillation amplitude level decreases, the detection output As the detection object 11 moves away and the oscillation amplitude level increases, the detection output increases.

  The detection circuit unit 7 is a processing circuit having a microcomputer configuration that detects that the detection object 11 is present when the detection object 11 approaches, the oscillation amplitude level decreases, and the detection output decreases to a detection threshold. A function is provided that can correct the detection threshold so that the operating distance when approaching and performing the detection operation with the detection threshold matches the predetermined operating distance. In this case, a point corresponding to a predetermined working distance is called a working distance adjustment point, and this working distance adjustment point is a target point to be adjusted to this working distance adjustment point when correcting the detection threshold.

  As shown in FIG. 2, the detection circuit unit 7 includes a detection threshold value storage unit 71 that stores a detection threshold value converted into an operation distance in a rewritable manner, and an operation distance adjustment point storage unit 72 that stores an operation distance adjustment point in a rewritable manner. , A calculating means 73 for performing a correction calculation of the detection threshold so as to make the operating distance coincide with a predetermined operating distance, and a control means 74 for controlling the storage means 71 and 72 and the calculating means 73. The computing means 73 and the control means 74 can be collectively referred to as control means. This control means is constituted by a CPU. 75 is an AD conversion interface for AD-converting the detection output from the rectifier circuit unit 5, 76 is an output port for outputting a signal to the output circuit unit 9, 77 is a program memory for storing a control program of the control means 74, and 78 is This is an external interface for taking in data for setting detection thresholds and operating distance adjustment points in the storage means 71 and 72 from the outside to the storage means 71 and 72. The two storage means 71 and 72 are two in structure, but can be constituted by one data memory. The work memory which is the work area of the control means 74 and other illustrations are omitted. To do.

  The control unit 74 inputs the detection output OUT from the rectifier circuit unit 5 corresponding to the oscillation amplitude level of the oscillation circuit unit 3 to the calculation unit 73 via the AD conversion interface 75 and also the digital value in the detection threshold storage unit 71. The initial detection threshold value Vst1 is input to the calculation means 73. When the result of the calculation by the calculation means 73 is Voff and there is no detected object, the control means 74 DA-converts the calculation result by the AD conversion interface 75 and outputs the low level signal L to the output circuit unit 9. When the detection object 11 approaches and the calculation result of the calculation means 73 indicates that the detection output OUT is small and matches the initial detection threshold value Vst1, the control means 74 displays the calculation result at the output port 76. A high level signal H that is present is output to the output circuit unit 9. The approach distance of the detection object 11 with respect to the proximity sensor 1 at the time when the high level signal H is output is the operation distance. Therefore, if the initial detection threshold value Vst1 is large, the detection object 11 approaches the proximity sensor 1 when the detection object 11 moves away from the proximity sensor 1, and the operation distance becomes long. The operating distance is shortened by operating at a close distance. In any case, when the operating distance is different from the predetermined operating distance, it is necessary to adjust the operating distance to the predetermined operating distance.

  In this case, before adjusting the operating distance such as before shipment from the factory, the detection threshold value storage unit 71 stores the initial detection threshold value Vst1 as the detection threshold value before adjusting the operating distance. Accordingly, the detection output OUT matches the initial detection threshold Vst1 before the detection output OUT from the rectifier circuit unit 5 decreases to a level corresponding to the operation distance adjustment point Von determined corresponding to the predetermined operation distance. As a result, a high level signal H indicating that there is a detection object is output at a distance deviating from a predetermined operating distance. This is a state in which the operating distance is not adjusted to the operating distance adjustment point Von.

  Therefore, the calculation means 73 calculates a difference ΔV between the initial detection threshold value Vst1 and the operating distance adjustment point Von. If the initial detection threshold value Vst1> the operating distance adjustment point Von, the difference ΔV is positive, and the calculation means 73 subtracts the difference ΔV from the initial detection threshold value Vst1. This subtracted value is set as a correction detection threshold Vst2. The control unit 74 rewrites the detection threshold value stored in the detection threshold value storage unit 71 from the initial detection threshold value Vst1 to the corrected detection threshold value Vst2.

  The calculating means 73 calculates a difference ΔV between the initial detection threshold value Vst1 and the operating distance adjustment point Von. Unlike the above, this difference ΔV is such that the initial detection threshold value is Vst1 ′ <the operating distance adjustment point Von. In this case, the calculation means 73 sets the value obtained by adding the difference ΔV from the initial detection threshold Vst1 ′ as the corrected detection threshold Vst2. The control unit 74 rewrites and controls the detection threshold value stored in the detection threshold value storage unit 71 from the initial detection threshold value Vst1 ′ to the corrected detection threshold value Vst2.

  The operation distance adjustment method regarding the above is demonstrated with reference to FIG. 3, FIG. 3A and 4A show before the operating distance adjustment, and FIGS. 3B and 4B show after the operating distance adjustment. 3A and 3B, when Voff is not detected, Vst1 is an initial detection threshold, Vst2 is a correction detection threshold, Von is an operating distance adjustment point, and ΔV is a difference between the initial detection threshold Vst1 and the operating distance adjustment point Von. is there. The operating distance adjustment point Von is a point corresponding to a predetermined operating distance D2.

  Before the operating distance adjustment, as shown in FIG. 3A, the initial detection threshold value Vst1 is located between the non-detection time Voff at the time of return and the operating distance adjustment point Von. As indicated by the arrow, since the proximity sensor 1 approaches the detection object 11 and the detection output OUT already matches the initial detection threshold Vst1 at the distance D1 before approaching the predetermined operation distance D2, the distance D1 is operated. A signal H indicating that the detection object 11 is present is output as a distance. In the example of FIGS. 3 and 4, the operating distance D2 at the operating distance adjustment point Von is shorter than the operating distance D1.

  After adjustment of the operating distance, the detection threshold value written in the detection threshold value storage means 71 as shown in FIG. 3B by the control means 74 according to the calculation result of the calculation means 73 in FIGS. 3B and 4B. Is rewritten and corrected from the initial detection threshold value Vst1 to the correction detection threshold value Vst2 that coincides with the operating distance adjustment point Von so that the operating distance adjustment point Von = correction detection threshold value Vst2 is indicated by the arrow in FIG. As described above, when the proximity sensor 1 approaches the detection object 11 and the detection output OUT decreases, and the detection output OUT coincides with the correction detection threshold value Vst2 at the approach distance D2, the signal H indicating that there is a detection object is output. At this time, the distance between the detection object 11 and the proximity sensor 1 is D2, which coincides with a predetermined operating distance corresponding to the operating distance adjustment point Von.

  In the above, the initial detection threshold is Vst1, which is equal to or higher than Von. However, the same applies to the case of Vst1 ′ where the initial detection threshold is equal to or lower than Von as shown in FIGS. 5 (a) and 6 (a) show before operating distance adjustment, and FIG. 5 (b) and FIG. 6 (b) show after operating distance adjustment.

  In this case, as shown in FIGS. 5A and 6A, even when the operating distance is adjusted, even if the detection object 11 approaches and the detection output OUT becomes small and the operating distance adjustment point Von is reached, detection is possible. The signal H with an object is not output, and the signal H with a detected object is output when the detection output OUT is further reduced to the detection threshold Vst1 ′. As a result, even if the detected object 11 approaches the proximity sensor 1 and passes through the operating distance adjustment point Von, it does not detect that the detected object 11 is present but detects the operating distance D1 ′.

  After the operating distance adjustment, the control unit 74 according to the calculation result of the calculating unit 73 rewrites the initial detection threshold value Vst1 ′ stored in the detection threshold value storage unit 71 to the detection threshold value Vst2 that matches the operating distance adjustment point Von. Is corrected. As a result of this rewriting, as shown in FIG. 5B and FIG. 6B, when the detection object 11 approaches and the detection output OUT decreases to reach the operating distance adjustment point Von, the detection threshold value Vst2 is reached and detected. As a result of outputting the object presence signal H and the detection output OUT, the detection object presence signal H is output at the operating distance adjustment point Von. At this time, the distance between the detection object 11 and the proximity sensor 1 is D2, which coincides with the operating distance adjustment point Von.

  Although the example in which the detection circuit unit 7 is configured by a microcomputer has been described above, the detection circuit unit 7 may be configured by a logic circuit configuration as illustrated in FIG. For example, the detection circuit unit 7 includes a difference calculation circuit unit 7a and a correction circuit unit 7b, and the difference calculation circuit unit 7a receives the operating distance adjustment point Von and the initial detection threshold value Vst1, and the difference ΔV Is calculated. In the correction circuit unit 7b, when the difference ΔV is positive, the difference ΔV is subtracted from the initial detection threshold Vst1, and when the difference ΔV is negative, the difference ΔV is added from the initial detection threshold Vst1, and the result is obtained as a correction detection threshold Vst2. To do. In FIG. 7, the detection threshold value storage means and the storage means for the operating distance adjustment point Von are not shown.

  As described above, in the embodiment, the detection threshold value written in the detection threshold value storage unit 71 is rewritten and corrected from the initial detection threshold values Vst1 and Vst1 ′ to the detection threshold value Vst2 that matches the operating distance adjustment point Von. It is possible to automatically adjust the operating distance to the operating distance adjustment point Von without adjusting the resistor.

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. 3A is a diagram showing the relationship among the non-detection output Voff, the operating distance adjustment point Von, and the initial detection threshold Vst1 before the operating distance adjustment is larger than the operating distance adjustment point Von, and FIG. 3B. FIG. 4 is a diagram showing a relationship among a non-detection output Voff, an operation distance adjustment point Von, and a detection threshold value Vst2 after adjustment of the operation distance, in which the detection threshold value is matched with the operation distance adjustment point from FIG. 4A is a diagram showing a distance relationship between the detection object corresponding to FIG. 3A and the proximity sensor, and FIG. 4B is a distance relationship between the detection object corresponding to FIG. 3B and the proximity sensor. It is a figure which shows FIG. 5A is a diagram showing the relationship among the non-detection output Voff, the operation distance adjustment point Von, and the initial detection threshold Vst1 before the operation distance adjustment, where the initial detection threshold Vst1 is smaller than the operation distance adjustment point Von. ) Is a diagram showing the relationship among the non-detection output Voff, the operating distance adjustment point Von, and the detection threshold value Vst2 after adjusting the operating distance, in which the detection threshold is matched with the operating distance adjustment point from FIG. FIG. 6A is a diagram showing the distance relationship between the detection object corresponding to FIG. 5A and the proximity sensor, and FIG. 6B is the distance relationship between the detection object corresponding to FIG. 5B and the proximity sensor. It is a figure which shows FIG. 7 is a diagram showing a modification of the detection circuit unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Proximity sensor 3 Oscillation circuit part 5 Rectifier circuit part 7 Detection circuit part 71 Detection threshold value memory | storage means 72 Operating distance adjustment point memory | storage means 73 Calculation means 74 Control means 9 Output 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 And a proximity sensor whose operation distance is the distance from the detection object at the time when the operation signal is output,
A method for adjusting an operating distance of a proximity sensor, wherein the operating distance is adjusted by correcting a detection threshold value in the detection circuit unit.   A detection threshold value is stored in the storage means, and when the operating distance when moving closer to the detection object and operating with the detection threshold value does not match the predetermined operating distance, the detection threshold value is adjusted to the predetermined operating distance. 2. The operating distance of the proximity sensor according to claim 1, wherein the operating distance is adjusted by matching the operating distance adjustment point, and adjusting the operating distance by rewriting and storing the corrected detection threshold value in the storage means. Adjustment method. 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 an operating distance as a distance from a detection object at the time when the operation signal is output,
The detection circuit unit adjusts the operation distance to adjust the detection threshold to the predetermined operation distance when the operation distance when the detection object approaches the detection object and operates with the detection threshold does not match the predetermined operation distance. A proximity sensor comprising a circuit function of adjusting an operating distance by correcting so as to coincide with a point.   Storage means for storing the rewritten detection threshold, control means for rewriting the detection threshold to the storage means, and control means for controlling the adjustment of the operating distance with the rewritten detection threshold; The proximity sensor according to claim 3, further comprising:   The proximity sensor according to claim 4, wherein the control means is constituted by a CPU.

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