JPH09238064A - Detection switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a user to easily recognize a margin in use being a difference between an adjusted threshold level and the output of a detection circuit by using a threshold level adjustment type detector switch. SOLUTION: A CPU 4 has functions of a comparator means 4 comparing output from an A/D converter 3 with a prescribed threshold level and a threshold level adjustment means 4b adjusting a threshold level of the comparator means 4a. A comparison output of the comparator means 4a is outputted externally via an output circuit 5 as an object detection signal. An operation section 6 inputs entry of an operation mode and of automatic sensitivity setting, up/ down input to manually increase/decrease a threshold level, and an off-point threshold level at which an output is cleared after an object is once sensed to the CPU 4. To the CPU 4, a margin output circuit 7 is connected, which outputs a difference between a threshold level set by a threshold level adjustment means 4b and an output level at present from the A/D converter 3 as a margin. Since the margin is recognized by the user at mounting or at sensitivity setting of the like, a proper mount position is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection switch, such as a proximity switch or a photoelectric switch, which outputs a detection output depending on the presence or absence of an object and the distance thereof, and more particularly to a detection switch capable of outputting a margin during operation thereof. Is.

[0002]

2. Description of the Related Art Conventionally, a detection switch, for example, a high-frequency oscillation type proximity switch has a coil in a portion for detecting an object, and an oscillation circuit is constructed by including this coil. When the amplitude or frequency exceeds a predetermined value due to a decrease in the frequency or a change in the oscillation frequency, the presence or absence of an object is detected and an output is output to the outside. In such a proximity switch, the sensitivity is set manually or by an automatic sensitivity setting operation. When the automatic sensitivity is set, the sensitivity is automatically set according to the procedure pre-installed in the device. Further, the user also manually sets the sensitivity appropriately. For the detection switch, the sensitivity adjustment type detection switch that adjusts the detection distance of the object by adjusting the sensitivity of the detection circuit itself, and the distance is adjusted by changing the threshold value of the comparison means that distinguishes the detection output while keeping the sensitivity of the detection circuit constant. There is a threshold adjustment type detection switch. The detection switch obtains an output according to the change of the detection target by the detection circuit, and detects the object by discriminating the output.

[0003]

However, the automatic sensitivity adjustment in such a detection switch is set for the purpose of being used in various environments and by an unspecified number of users. In reality, it is difficult to realize the optimum automatic sensitivity adjustment for the detection state. Especially when the difference between the detection and the return is small, the automatic sensitivity adjustment may be difficult. Therefore, when the user performs a sensitivity adjustment different from the automatic sensitivity adjustment, the automatic sensitivity adjustment may be performed again at a position slightly different from the position where the user actually passes during teaching, or a manual sensitivity adjustment may be attempted. When the sensitivity is automatically set in this way, there is a drawback in that it is not possible to recognize what kind of operation it is or what kind of operation state it is in during use. Therefore, it is difficult for the user to readjust the sensitivity to a desired one, and there is a drawback that the user may continue to use it without noticing that it is being used in an improperly attached state, resulting in a malfunction. Further, when a disturbance occurs in the detection switch after setting the threshold value, the change in the settable range cannot be recognized.

The inventions according to claims 1 to 7 of the present application have been made in view of such conventional problems, and in a threshold adjustment type detection switch, the threshold and the detection circuit are The purpose is to allow the user to easily recognize the margin in use, which is the difference from the output. In addition to this, it is an object of the invention of claim 6 to display a range in which the sensitivity can be set in a state where a disturbance is received.

[0005]

According to a first aspect of the present invention, there is provided a detection circuit for changing an output according to a change in a detection target, and a comparison means for discriminating the output of the detection circuit by a threshold value.
Threshold adjusting means for adjusting the threshold of the comparing means, operating means for inputting threshold adjustment by the threshold adjusting means, output value according to a detection target obtained from the detection circuit, and threshold adjusted by the threshold adjusting means. And a margin output means for outputting the difference between and to the outside.

In the invention of claim 2 of the present application, the threshold value adjusting means directly changes the threshold value by an input from the operating means.

In the invention of claim 3 of the present application, the threshold adjusting means sets an on-point threshold for detecting an object and an off-point threshold for reversing non-detection of the object. The off margin up to the on-point threshold in the off state and the on margin up to the off-point threshold in the on state are output.

According to a fourth aspect of the present invention, a detection circuit that changes an output according to a change in a detection target, a comparison unit that discriminates an output of the detection circuit by a threshold value, and a threshold value that adjusts the threshold value of the comparison unit. Adjusting means, operating means for inputting threshold adjustment by the threshold adjusting means, threshold value / margin for simultaneously outputting the threshold value adjusted by the threshold adjusting means and the output value according to the detection target obtained from the detection circuit And an output means.

In the invention of claim 5 of the present application, the threshold value adjusting means directly changes the threshold value by an input from the operating means.

According to a sixth aspect of the present invention, the threshold value adjusting means sequentially operates the adjustable range, and the disturbance detecting means detects the sensitivity adjusting range in which the output is obtained from the comparing means. The margin output means is characterized in that it simultaneously outputs the threshold adjustment threshold value detected by the disturbance detection means.

In the invention of claim 7 of the present application, the threshold value adjusting means sets an on-point threshold value for detecting an object and an off-point threshold value for reversing the non-detection of the object.
The margin output means is characterized by outputting the off margin up to the ON point threshold in the OFF state and the ON margin up to the OFF point threshold in the ON state.

Claims 1 of the present application having such features
According to the second aspect of the invention, the threshold value of the comparing means is adjusted by the threshold value adjusting means. Then, the difference between the set threshold value and the current output value obtained from the detection circuit is output as the allowance from the allowance output means. Further, in the invention of claim 3, the difference between the threshold value of the ON point for detecting the object and the current value is set as the ON margin, and the difference between the threshold value of the OFF point when the object is not detected and the current value is set as the OFF margin, and these are defined as The margin output means outputs the data. Further, in the inventions of claims 4 to 7, the present value and the threshold value are displayed as they are instead of the difference between the current value and the threshold value as the margin. In the invention of claim 6, when a disturbance occurs In addition, the disturbance detection means detects the adjustable range of the threshold value and displays them simultaneously.

[0013]

1 is a block diagram showing the configuration of a high-frequency oscillation type proximity switch according to a first embodiment of the present invention. In FIG. 1, the oscillator circuit 1 includes a coil L1,
This is a detection circuit whose oscillation amplitude changes depending on the external state, in this case, the proximity of a metal body. The output of the oscillation circuit 1 is given to the peak hold circuit (P / H circuit) 2. The peak hold circuit 2 is reset every fixed time and holds the peak value of the oscillation amplitude, and its output is output to the A / D converter 3. The A / D converter 3 converts an analog signal input at a predetermined timing into a digital value and converts it into a CP value.
It is output to U4. CPU 4 is A / D converter 3
It has the functions of a comparing means 4a for comparing the output obtained from the above with a predetermined threshold level and a threshold adjusting means 4b for adjusting the threshold of the comparing means. The comparison output of the comparison means 4a is output to the outside as an object detection signal via the output circuit 5. The operation unit 6 inputs to the CPU 4 an operation mode and an input of automatic sensitivity setting, an up / down input for manually raising and lowering a threshold value, and an off point threshold value for turning off the output after once detecting an object. A margin output circuit 7 is connected to the CPU 4. The margin output circuit 7 outputs the difference between the threshold value set by the threshold value adjusting means 4b and the current output level from the A / D converter 3 as a margin, as will be described later. The output value is displayed on the display 8.

Next, the operation of this embodiment will be described.
A curve A in FIG. 2A shows the amplitude of the oscillation circuit 1 with respect to the distance to the detection object. The oscillation amplitude becomes substantially constant as the distance increases, and gradually decreases as the distance approaches. This proximity switch is in a state where oscillation continues at a low level even when the object is at the closest position. Therefore, the threshold value V1 up to the distance where the amplitude is constant is the upper limit value of the settable range, that is, the maximum sensitivity value, and the threshold value V1 is always off.
4 is the minimum threshold value that can be set, that is, the minimum sensitivity value.
By adjusting the threshold value within this range, sensitivity in an arbitrary range up to the distance D1 can be obtained. At the time of automatic sensitivity adjustment, the threshold value is set to any one of V4 to V1 so that an object can be detected as described later. As the threshold value, a threshold value at which an output is normally turned on when an object approaches from a distance, that is, an on-point threshold value, and an off-point threshold value at which an output is once turned off and then the output is turned off, are two.
The point is set.

In this way, if the threshold value is set in advance, if the object actually approaches, the A /
The levels from the D converter 3 are compared by the comparison means 4a. The margin output circuit 7 detects the difference between the current A / D conversion value and the on-point threshold value and the off-point threshold value as the margin.
For example, when an object approaches and the output is turned on, the output is inverted and turned off again if the off point threshold is exceeded. Therefore, the difference between the current amplitude value and the off-point threshold value is referred to as a margin that does not turn off accidentally in the on state, that is, an on margin.
The ON margin is calculated from the set threshold and the current value and displayed on the display unit 8. FIG. 3A is a diagram showing a display example of this margin. The display device 8 is a bar graph type level display device, and displays the level of the allowance by the number of lit LEDs. The margin output circuit 7 according to the present embodiment displays at least this on margin, but it may display the off margin when the output is off. That is, when the object goes away and the output is turned off, the output is inverted next when the object comes closer and falls below the on-point threshold. Therefore, the difference between the current amplitude value and the on-point threshold value is defined as the off margin. When the output is off, this off margin may be displayed. In this case, either the ON margin or the OFF margin is displayed as shown in FIG. 3A depending on the ON / OFF state of the output.

Next, an example of setting the threshold will be described. FIG.
4A is a diagram showing the relationship between the proximity switch 10 and the objects A, B, and C, FIG. 4B is a diagram showing the relationship between the distance and the oscillation amplitude, and FIG. 5 is a flowchart showing the setting of the threshold value. In this flowchart, when an object passes in the direction of the arrow in front of the proximity switch 10 as shown in FIG. 4A, the passage of the object B at a distance n from the proximity switch is detected and the position f away from this is detected. It is assumed that the thresholds are set so that the other objects A and C existing in are not detected. In this case, it is assumed that the wall surface 11 of the metal body is located far away from the proximity switch 10 and is affected by this. FIG. 4B shows a state in which the proximity switch reduces the maximum amplitude M to L by the wall surface 11.

When the sensitivity is set in the flow chart shown in FIG. 5, the mode is first switched to the sensitivity setting mode (step S1). And the distance n in front of the proximity switch 10
The object B is placed at the position of and the on-point teach command is input. Then, the amplitude value N of the oscillation circuit obtained at that time
Is read into register x (step S3), step S4
Then, it is checked whether x is larger than the value S at the closest position of the sensitivity characteristic curve of FIG. 4 (b). If it is less than this value, the sensitivity cannot be adjusted and an error is output. If it exceeds this value, the process proceeds to step S5. Next, the OFF point teach command is input in a state where the object is turned off to be distinguished, that is, the object A or C is arranged at the position of the distance f. Then, the process proceeds to step S6, and the amplitude value F obtained at this time is read into the register x. Then, the process proceeds to step S7, and the amplitude value L at which the value of the register x becomes the maximum amplitude in this environment.
To determine whether or not. Also in this case, if it is less than this state, the sensitivity cannot be adjusted and error processing is performed. If it is less than this value, the process proceeds to step S8 to calculate the on-point threshold value T. The on-point threshold value T is set as the threshold value at the midpoint between the two input amplitude values N and F. Next, in step S9, a level higher than this by 10% is set as the off-point threshold U. Then, in step S10, it is determined whether the off-point threshold U is F or less. If U is greater than or equal to F, the sensitivity cannot be adjusted, so error processing is performed. If U is not greater than F, the process proceeds to step S11 to display the completion of sensitivity adjustment. If the normal detection mode is selected in step S12, the sensitivity adjustment process ends.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. The proximity switch of this embodiment has almost the same configuration as that of the first embodiment, and the margin output circuit 7
The threshold / margin output circuit 21 is provided so as to output the threshold and the margin simultaneously. The display 22 is a display for displaying the set values of the on and off points and the current amplitude value as shown in FIG. 3 (b). More CPU
4A is the above-mentioned CPU comparison means 4a and threshold adjustment means 4
In addition to b, the disturbance detection means 4c is included. In this case, as shown in FIG. 3B, the on-point threshold value is displayed at the left end position of the bar graph type display device 22, and the off point threshold value is also displayed at the right end position of the bar graph type display device. Then, the amplitude up to the detected object is displayed at the center position. Since the oscillation amplitude of this proximity switch monotonically increases with the distance to the object as shown in FIG. 2A, the display of the oscillation amplitude has the same meaning as the display of the distance. For example, when the object A or C shown in FIG. 4A passes, the amplitudes (distances) of the objects A and C are displayed as shown in FIG. 3C. Therefore, in the state shown in FIG. 3C, the difference between the distance to the object and the on-point threshold value at this time corresponds to the off margin. Further, when the object B to be detected passes, the value becomes equal to or lower than the on-point threshold value, so that the output circuit 5 outputs an object detection signal. At this time, the display 22 is shown in FIG.
It is displayed as shown in (b). In this state, the difference between the distance to the object and the off point threshold corresponds to the on margin.

In the first and second embodiments, the on-point and off-point thresholds are set using the automatic sensitivity adjustment function, but the thresholds can be manually raised or lowered. In this case, the threshold value is directly raised or lowered by the operation unit 6 using the up key or the down key for adjustment. Also in this case, the margin can be displayed as shown in FIG. 3A from the difference between the current amplitude value and the ON point threshold value to the ON point threshold value. Also in the second embodiment, the margin can be recognized by displaying the set value and the current amplitude.

If there is a disturbance detection input to the disturbance detecting means 4c, the range of the adjustable threshold value is changed in that state,
It waits for an output change from the comparison means 4a. Assuming that the distance and amplitude characteristics are obtained by the curve A shown in FIG. 2A when the proximity switch is shipped from the factory, and the upper and lower limit values of the oscillation amplitudes of V1 and V4 are obtained, the temperature change and the ambient The amplitude characteristic with respect to the distance changes as shown by the curve A ′ in FIG. 2B depending on the environmental condition at the time of use, such as the influence of metal. Therefore, the threshold value is gradually increased, and the upper limit value V1 ′ of the threshold value at that time can be detected by the range in which the output of the comparison means 4a is reversed. The lower limit value V4 ′ may be determined by bringing an object close to the object and lowering the threshold value, or the lower limit value V4 ′ may be estimated from a decrease in the amplitude value. 7 (a) and 7 (b) show the limit value on V1 'and the limit value off V4' in black in the present value column when the proximity switch is attached and there is disturbance. When displaying the disturbance, it is necessary to previously associate the upper limit value V1 and the lower limit value V4 of the threshold value detected at the time of factory shipment of the proximity switch so as to correspond to the full scale of the display unit 22. By doing so, it can be recognized that the settable range of the amplitude value has decreased from the upper and lower ends of the display due to the influence of disturbance as shown in FIG. In addition to this limit value, the on-point threshold value, the off-point threshold value, and the current value are displayed as shown in FIG.

In this way, the settable range in the presence of disturbance, the threshold value currently set within the range, and the distance to the object in use can be recognized, so that the mounting work at an appropriate position must be performed. You can Further, it becomes easy to determine the state in use and the presence or absence of disturbance.

FIG. 8 is a block diagram showing the structure of a high frequency oscillation type proximity switch according to the third embodiment of the present invention. The proximity switch of this embodiment is a proximity switch that detects the proximity of an object based on a change in the oscillation frequency, and uses the oscillation frequency as a threshold. The oscillation circuit 31 of the proximity switch is composed of a resonance circuit including the detection coil L2 and an amplifier, and the output thereof is input to the waveform shaping circuit 32. The waveform shaping circuit 32 converts the oscillation output into a square wave, and its output is input to the frequency divider 33. On the other hand, the proximity switch includes an oscillator circuit 34 that oscillates a reference clock signal.
The output is divided by the frequency divider 35 and input to the CPU 36. CPU 36 is frequency divider 35
Counting means 36a for counting the number of pulses obtained from the frequency divider 33 at the timing of the predetermined level, and comparing means 36b for comparing the count value of the counting means 36a with a threshold value.
It has a function of a threshold value adjusting means 36c for adjusting a threshold value and a function of a disturbance detecting means 36d for detecting a disturbance. The output from the comparison means 36b is given to the output circuit 37, and the object detection signal is output to the outside. Further, an automatic sensitivity adjustment signal, an interrupt signal for detecting a disturbance, and a threshold up / down signal at the time of manual sensitivity adjustment are input from the operation unit 38. Then, the threshold value adjusted by the threshold value adjusting means 36c of the CPU 36, the count value of the counting means 36a when the disturbance is detected, and the like are given to the threshold value / margin output circuit 39. Similar to the second embodiment, the threshold / margin output circuit 39 outputs the limit value of the frequency setting, the threshold and the margin to the display 40.

FIG. 9 is a graph showing changes in the oscillation frequency with respect to the distance to the detected object. In the present embodiment, the oscillation frequency changes in inverse proportion to the distance to the object, so a threshold value is set for the count value of the counting means 36a that measures the frequency. Further, the settable range is the lower limit frequency f1 at which the oscillation frequency changes at the furthest distance from the oscillation frequency f4 when the object is closest to the proximity switch. Therefore, the sensitivity can be set by changing the threshold frequency within this range by automatic sensitivity adjustment or manual sensitivity adjustment. Because of this relationship, displaying the frequency f3 that is the on-point threshold value and the frequency f2 that is the off-point threshold value is equivalent to displaying the distance. Also in this case, the on point (f3) and the off point (f2) can be set independently. That is, as shown in FIGS. 10A and 10B, it is possible to display the position where the threshold is set and the current position of the object by the frequencies f2 and f3 that are thresholds and the frequency at that time. Similarly, the on margin and the off margin can be recognized from the difference between the current frequency and the threshold value set for the frequency. Also in this embodiment, the ON margin itself or the ON margin and the OFF margin may be displayed.

Further, it is possible to detect the sensitivity adjustment range in the case where there is a disturbance due to an interrupt input from the operation unit 38. Also in this case, the threshold of the oscillation frequency can be continuously changed, and the range in which the output is inverted can be set as the detection range. The ON limit value f1 ′ and the OFF limit value f4 ′ in the presence of this disturbance are displayed on the display 40 as shown in FIG. 10 (c). This allows the user to recognize the threshold value set in the presence of disturbance. Similar to each of the above-described embodiments, it is possible to simultaneously set or display the change of the limit value and the off-point threshold when the influence of the disturbance occurs in the use environment.

Although the present embodiment describes the high frequency oscillation type proximity switch, the present invention can be applied to various types of proximity switches, ultrasonic switches and photoelectric switches.

[0026]

As described in detail above, according to the inventions of claims 1 to 3 of the present application, since the margin can be recognized at the time of mounting or at the time of setting sensitivity, an appropriate mounting position can be selected. . Since the margin is displayed even during use, it is possible to stably recognize whether the object is in the object detection or non-detection state. Further, in the third aspect of the invention, the threshold values for turning on and off can be set at the same time. Moreover, claim 4 to
In the seventh aspect, since the threshold value and the current value are displayed as they are, it is possible to determine whether the sensitivity setting value is a proper value at the time of mounting. In addition, the margin can be recognized during normal operation, and it is possible to determine whether or not the detection switch is kept in the correct detection state. Further, in claim 6, since the settable range is displayed when there is the influence of the disturbance, it is necessary to recognize how the threshold and the adjustable range of the sensitivity are changed by the disturbance when the disturbance occurs. You can Therefore, if the margin between the user and the set sensitivity or threshold is small, the user can take measures such as changing the mounting method or sensitivity or removing the influence of disturbance.

[Brief description of drawings]

FIG. 1 is a block diagram of a high frequency oscillation type proximity switch according to a first embodiment of the present invention.

FIG. 2 is a graph showing a change in oscillation amplitude with respect to a distance to an object.

3A is a diagram showing a display example of a margin according to the first embodiment, and FIGS. 3B and 3C are diagrams showing a display example of a margin according to the second embodiment.

FIG. 4 is a diagram showing a relationship between a proximity switch and an object when setting a threshold value.

FIG. 5 is a flowchart showing a threshold setting operation.

FIG. 6 is a block diagram of a high frequency oscillation type proximity switch according to a second embodiment of the present invention.

FIG. 7 is a display example showing the influence of disturbance.

FIG. 8 is a block diagram showing a configuration of a high frequency oscillation type proximity switch according to a third embodiment of the present invention.

FIG. 9 is a graph showing a change in frequency with respect to a distance to a detected object.

FIG. 10 is a diagram showing a display example of the display according to the present embodiment.

[Explanation of symbols]

 1,31 Oscillation circuit 2 P / H circuit 3 A / D converter 4,23 CPU 4a, 36b Comparison means 4b, 36c Threshold adjustment means 4c, 36d Disturbance detection means 5 Output circuit 6,38 Operating part 7 Margin output circuit 8, 22, 40 Display 21, 39 Threshold / margin output circuit 32 Waveform shaping circuit 33, 35 Dividing circuit 36a Counting means

Claims (7)

[Claims] 1. A detection circuit that changes an output according to a change in a detection target, a comparison unit that discriminates an output of the detection circuit by a threshold, a threshold adjustment unit that adjusts a threshold of the comparison unit, and the threshold adjustment. An operating means for inputting threshold value adjustment by means, and a margin output means for outputting to the outside a difference between an output value obtained from the detection circuit according to a detection target and a threshold value adjusted by the threshold value adjusting means. A detection switch characterized by: 2. The detection switch according to claim 1, wherein the threshold value adjusting means directly changes the threshold value by an input from the operating means. 3. The threshold value adjusting means sets an on-point threshold value for detecting an object and an off-point threshold value for reversing non-detection of the object, and the margin output means is an on-point value in an off state. The detection switch according to claim 1, wherein the off margin up to the threshold value and the on margin up to the off point threshold value in the on state are output. 4. A detection circuit that changes an output according to a change in a detection target, a comparison unit that discriminates an output of the detection circuit by a threshold, a threshold adjustment unit that adjusts a threshold of the comparison unit, and the threshold adjustment. And a threshold value / margin output means for simultaneously outputting the threshold value adjusted by the threshold value adjusting means and the output value corresponding to the detection target obtained from the detection circuit. A detection switch characterized by the above. 5. The detection switch according to claim 4, wherein the threshold value adjusting means directly changes the threshold value by an input from the operating means. 6. The threshold value adjusting means sequentially operates the adjustable range, and has a disturbance detecting means for detecting a sensitivity adjusting range in which an output is obtained from the comparing means, and the threshold value / margin output means, The detection switch according to claim 4, wherein the limit value of the threshold value adjustment detected by the disturbance detection means is simultaneously output. 7. The threshold adjusting means sets an on-point threshold for detecting an object and an off-point threshold for reversing non-detection of the object, and the threshold / margin output means is in an off state. The detection switch according to claim 4, wherein the off margin up to the on point threshold and the on margin up to the off point threshold in the on state are output.