JP2000111315A - Photoelectric sensor and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly align the threshold value of a plurality of photoelectric sensors by easily setting the threshold value of the photoelectric sensors to a specific value. SOLUTION: In a photoelectric sensor 11, specific threshold values (such as a maximum distance threshold value, a minimum distance threshold value) are stored in a nonvolatile memory at delivery from factory. If a setting mode turnover switch 34 is adjusted to the teaching mode (TEACH) and a set switch 32b is pushed at least for a specified time (3 seconds for example), the specific values stored at the delivery from factory are set. If the time when the set switch 32b is pushed is shorter than the specified time, the distance to the front object is set as the threshold value by a normal teaching operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sensor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a sensitivity setting method in a conventional sensor device, there is a teaching method sensitivity setting method used in a fiber type photoelectric switch or the like. When the mode changeover switch is set to the teaching mode and a push button for teaching or the like is pressed, the threshold value is automatically set based on the amount of received light at that time. Therefore, by performing teaching while irradiating the photoelectric switch with light having a constant intensity, the photoelectric switch can be set to a constant threshold value.

[0003] As a special setting method of the threshold value,
There is a maximum sensitivity setting. This is one of the methods for setting the photoelectric sensor to a specific threshold value, and is a method for setting the sensitivity of the photoelectric sensor to the maximum value. For example, if the teaching push button of the fiber-type photoelectric switch is kept pressed for 3 seconds or more, regardless of the actual amount of received light at that time, the light-emitting gain and the light-receiving gain will be the largest, so that the detection distance will be the longest and the fiber-type photoelectric switch The switch is set to maximum sensitivity.

[0004]

However, the above-mentioned fiber type photoelectric switch detects an object passing between the light projecting portion and the light receiving portion to be in a light blocking state. In contrast, a photoelectric switch that operates in accordance with the distance of an object (distance setting type photoelectric switch) has a minimum value and a maximum value in the distance setting range, and therefore it is necessary to set a plurality of specific threshold values. In the conventional setting method, the minimum value of the distance setting range cannot be set.

Further, in the distance setting type photoelectric switch, since there is a dead zone where light does not enter at a close distance, if an object is placed in front of the photoelectric switch to set a minimum value, the object is located at a distance shorter than the minimum setting distance. Even if there is a signal value, the signal value may be the same as the maximum set distance, and the method of acquiring the distance value by actually placing the object cannot distinguish the minimum value from the maximum value.

In the conventional photoelectric sensor, it is difficult to set the same threshold value for such different photoelectric sensors. Therefore, if a plurality of photoelectric sensors are installed in the same state and the same target object is to be detected, the objects are placed at the same distance in front of each photoelectric sensor, and each photoelectric sensor is set to have the same threshold value. Had to be adjusted one by one by teaching, which required a very troublesome work.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems. An object of the present invention is to set a specific threshold value easily, and to detect a detection object or a sensor. An object of the present invention is to provide a distance setting type photoelectric sensor which can be used without actually placing an object and teaching when a situation is constant, and a method for manufacturing the same.

[0008]

According to the photoelectric sensor of the present invention, a distance to a target object or a physical quantity equivalent to the distance is obtained by the principle of triangulation based on a light receiving position of the position detecting element, and the distance or an equivalent thereof is obtained. A photoelectric sensor having a function of comparing a physical quantity and a threshold value to determine a distance and a teaching function for setting the threshold value, for setting a specific threshold value by a predetermined operation. Is provided.

In the photoelectric sensor according to the first aspect, by performing a predetermined operation on the input means, a specific threshold value can be selected and set to the threshold value. Therefore, when it is desired to set the same threshold value for a plurality of photoelectric sensors, each of the photoelectric sensors can be operated only by operating the input means without actually placing an object in front of each photoelectric sensor and performing teaching one by one. Allow the sensor to set a specific threshold,
The threshold value of each photoelectric sensor can be easily set to the same value.

Here, the input means is not limited to a manually operated one such as a switch provided in the photoelectric sensor, but also includes a case where a specific threshold value is set by an external signal input to the photoelectric sensor. Further, the physical quantity equivalent to the distance means not only a value converted into an electric signal or the like, but also a quantity corresponding to the distance one-to-one (for example, a constant multiplied by a distance or a constant added, a one-to-one correspondence). 1 mapped value) is also included.

In particular, in the second embodiment, the specific threshold is a maximum distance threshold or a minimum distance threshold. Only one of the maximum distance threshold and the minimum distance threshold may be stored, and the specific threshold may be selected, and both thresholds are stored and either one is stored. May be arbitrarily selected. Here, the maximum distance threshold corresponds to the maximum distance among the possible thresholds, and the minimum distance threshold corresponds to the minimum distance among the possible thresholds. .

If a maximum distance threshold or a minimum distance threshold can be set as a specific threshold, it is determined whether or not the object is located in an area closer to the maximum distance or farther than the minimum distance. It can be determined whether an object is located in the area. In particular, if the distance is set to the minimum distance threshold value, the setting can be made so that the hysteresis becomes minimum (minimum hysteresis setting).

According to a third aspect of the present invention, a plurality of discrete thresholds are stored in the photoelectric sensor, and the discrete thresholds can be arbitrarily selected from the discrete thresholds by operating the input means. It may be possible to set a specific selected threshold value. If a plurality of thresholds can be selected in this way, a necessary specific threshold can be selected according to the application, so that the versatility is further improved.

Even if a plurality of specific thresholds can be selected as described above, if the number of thresholds is selected, each photoelectric sensor can be set to the same threshold. .

Further, the photoelectric sensor according to an embodiment of the present invention is characterized in that it comprises means for outputting a set threshold value. It has a means to output the set threshold, so that the threshold set by teaching or trial and error is read visually or electrically, so that the threshold of each photoelectric sensor becomes the same value. Can be set to

In this embodiment, when it is desired to set a threshold value other than the specific threshold value stored in the photoelectric sensor for each photoelectric sensor, the operation can be facilitated.

According to a fifth aspect of the present invention, there is provided a method for manufacturing a photoelectric sensor of a photoelectric sensor, wherein an object is placed at a specified maximum distance or a minimum distance, and an actual measured value of a distance to the object at that time or a physical quantity equivalent thereto is obtained. It is stored as a threshold.

Therefore, by operating the input means of the photoelectric sensor in a predetermined manner and calling the stored maximum distance threshold value or minimum distance threshold value, the threshold value of the photoelectric sensor as in the photoelectric sensor of claim 2 can be obtained. Can be set as the maximum distance threshold or the minimum distance threshold.

According to a sixth aspect of the present invention, in the method for manufacturing a photoelectric sensor, the parameters included in the relational expression relating the light receiving position of the position detecting element and the distance of the target object or a physical quantity equivalent thereto are measured and corrected. Features.
Such a parameter is, for example, a linearity correction coefficient β as described in the embodiment.

The relational expression for calculating the distance from the light receiving position (or photocurrent) of the position detecting element includes a parameter. Such a parameter depends on the arrangement of the optical system in the photoelectric sensor. The parameter varies due to the error of the above, and even if the threshold is set by teaching or numerical input, the threshold varies for each photoelectric sensor.

However, since the parameters of this photoelectric sensor are actually measured and corrected at the time of manufacture, variations in parameters among the photoelectric sensors can be made very small, threshold values can be set accurately, and input means ( In particular, by inputting a threshold value from the input means capable of inputting numerical values, it becomes possible to input a specific threshold value to each photoelectric sensor and make the threshold values of each photoelectric sensor uniform.

In the method of manufacturing a photoelectric sensor according to the present invention, the non-light-incident determination level is actually measured and adjusted. The actual measurement adjustment of the non-light-incident determination level is performed using an object having a limiting reflectance. In the photoelectric sensor manufactured in this way,
The non-light-incident level is actually measured and adjusted, and the non-light-incident determination level is accurate, and the variation in the non-light-incident determination level between the photoelectric sensors is extremely small. Therefore, it becomes possible to input a specific threshold value to each photoelectric sensor and to make the threshold values of each photoelectric sensor uniform.

[0023]

(First Embodiment) FIG. 1 is a front view showing the appearance of a reflection type photoelectric sensor 11 according to an embodiment of the present invention. The electrical configuration of the photoelectric sensor 11 is shown in the block diagram of FIG. First, the electrical configuration will be described. The photoelectric sensor 11 includes a light emitting unit 12, a light receiving unit 13,
Signal processing unit 14, input unit 15, display unit 16, output circuit 1
7 and the like.

The light projecting section 12 includes a light emitting diode (LED)
And a light emitting circuit 19 for driving the light emitting element 19, a light emitting lens system (not shown), etc., and a pulse signal output from a clock terminal of the oscillation circuit 26. The light emitting element 19 is driven by the light emitting circuit 20 in synchronism, and pulse light is output forward from the light emitting element 19.

The light receiving section 13 includes a light receiving lens system 21, a position detecting element (PSD) 22, and two light receiving circuits 23f and 23r.
Consists of If the object 18 exists in front of the photoelectric sensor 11, the light projected from the light projecting unit 12 is reflected by the object 18,
The light is received by the position detecting element 22 through the light receiving lens system 21. At this time, if the position of the light spot formed on the position detecting element 22 is obtained, the object 18 can be obtained by the principle of triangulation.
The distance to can be obtained.

When the position detecting element 22 receives light, the two terminals of the position detecting element 22 have a light receiving current If corresponding to the light receiving position on the light receiving surface, ie, a distance to the object 18.
And Ir flow. The light receiving circuits 23f and 23r include an amplifier unit and an A / D conversion circuit, and the light receiving currents If and Ir output from the respective terminals of the position detection element 22 are voltage-converted and amplified by the amplifier unit. The light is converted into a digital signal by the conversion circuit, converted into light receiving signals Vf, Vr proportional to the light receiving currents If, Ir, and the averaged light receiving signals Vf, Vr are output from the light receiving circuits 23f, 23r.

The signal processing unit 14 is realized by a microcomputer including a memory and a peripheral unit. The function realized by the microcomputer is an arithmetic circuit 2
4, represented by a comparison circuit 25, an oscillation circuit 26, a setting circuit 27, and an input time measurement circuit 28.

The arithmetic circuit 24 includes the light receiving circuits 2 of the light receiving section 13.
The distance to the object 18 is evaluated based on the light receiving signals Vf and Vr output from 3f and 23r. Photoelectric sensor 11
The distance x from the object 18 to the object 18 can be obtained by the following equation (1) using the light receiving signals Vf and Vr. x = P + Q [Vf / (Vr + βVf)] (1) Here, P is called an offset constant and Q is called a span constant, and both are the geometrical arrangement and position of the optical system of the light projecting unit 12 and the light receiving unit 13. This is a constant determined by the length of the light receiving surface of the detection element 22. Β is a linearity correction coefficient for linearly correcting the light receiving characteristic of the position detecting element 22. However, if the distance to the object 18 is evaluated and the distance to the object 18 is compared with the threshold value Vth, X = Vf / (Vr + βVf) (2) without considering the entire equation (1). You only need to compare Therefore, inside the photoelectric sensor 11, the value of X defined by the above equation (2) is treated as the distance to the object 18 (a value equivalent to the distance).

As described above, the arithmetic circuit 24 sets the object 18
When the distance X to the distance is obtained, the distance information is output to the comparison circuit 25 and the feature quantity display 29.

The comparison circuit 25 compares and determines the distance X to the object 18 calculated by the calculation circuit 24 with a preset threshold value Vth (set distance), and determines the calculated distance X to the object 18 as a threshold. A judgment output composed of an ON signal or an OFF signal is generated according to the magnitude of the value Vth. Then, the comparison circuit 25 outputs the on / off signal to the output indicator 31 and the output circuit 17.

The setting circuit 27 stores and holds the set threshold value Vth as a digital value. In the setting circuit 27, the threshold value Vth can be set by operating the threshold value setting switch 32 of the input unit 15. Alternatively, a threshold value Vth can be set in the setting circuit 27 by setting a reference object in front of the photoelectric sensor 11 and performing a teaching operation using the input unit 15. The setting circuit 27 stores the detection mode and the output mode set by the operation from the input unit 15 and sets the mode of each unit such as the display unit 16.

The input time measuring circuit 28 measures a teaching operation time, that is, a time during which a set switch 32b described later is pressed.

The display section 16 is turned on / off from the comparison circuit 25.
An output indicator light 31 for displaying an OFF signal;
A threshold value display 29 for displaying the distance to the object or the position of the object 18; and a threshold value display 30 for displaying the threshold value Vth. As shown in FIG. 1, the output indicator 31 is configured by one LED or lamp, and is turned on or off according to the determination result (on signal, off signal) of the comparison circuit 25. Further, the feature quantity display 29 is configured by arranging a plurality of display segments 29a, 29b,... Made of a green light emitting diode in a line, and receives a calculation result (distance information) calculated by the calculation circuit 24 and detects and receives the result. The distance to the object 18 is displayed in a bar graph according to the mode (the display segments 29a and 29 which are turned on).
.., or the position of the object 18 is displayed by the lighting position of the display segment 29a, 29b,.

The threshold indicator 30 is composed of a plurality of display segments 30a, 30b,... Made of red light emitting diodes arranged in a line, and corresponds to the threshold Vth set by the setting circuit 27. One or two display segments 30a, 30b,... Are turned on. Each of the display segments 30a, 30b,.
The display segments 29a, 29b,.
It is located between them.

The output circuit 17 converts the on / off signal obtained from the comparison circuit 25 into a signal suitable for application to an external device for control or other purposes, and outputs the signal.

The input unit 15 includes a threshold setting switch 32 for inputting a threshold value Vth, a detection mode switch 33 for switching the detection mode of the display unit 16, and a setting mode switch for switching a setting method. 34, an output mode changeover switch 35. The setting contents of each switch are transmitted to the setting circuit 27, where they are set. That is, the detection mode changeover switch 33 displays the detection distance X to the object 18 on the feature quantity display 29 as a bar graph, and turns on / off the threshold value display 30.
A normal mode in which a threshold value Vth0 as an off boundary is turned on, a detection position of the object 18 is displayed on the feature amount display 29, and a zone display is performed on the threshold value display 30 with the upper limit value Vth2 and the lower limit value Vth1. Switch to zone mode. Further, when the setting mode changeover switch 34 is operated, each of the detection modes can be switched between the teaching mode, the adjustment mode, and the normal detection operation mode. When the setting mode changeover switch 34 is set to the teaching mode, the threshold value Vth can be set by the teaching method, and the setting circuit 27 saves the setting or change of the threshold value Vth. Also,
When the setting mode changeover switch 34 is set to the adjustment mode, the threshold setting switch 32 can be input. When the threshold setting switch 32 is operated to input the threshold Vth, the setting circuit 27 sets the threshold Vth0, The setting or change of the upper limit value Vth2 or the lower limit value Vth1 is saved.

The output mode switch 35 has a high light receiving level (reflected light is incident on the light receiving section 13).
Mode when the sensor output is turned on (output indicator 31
Turns on), and selects one of the modes in which the sensor output is turned on when the light receiving level is low (reflected light does not enter) (the output indicator 31 is turned on).

FIG. 1 shows an example of a specific configuration of the input section 15. Detection mode switch 33
Are switched between a normal mode (NORMAL) and a zone mode (ZONE). The setting mode changeover switch 34 is connected to the teaching mode (TE
ACH), an adjustment mode (ADJ), and a normal operation mode (RUN). The threshold setting switch 32 switches the lighting segments 30a, 30b,.
A set direction switch 32a and a set switch 32b for setting the moving direction of the camera are set.
When 2b is pressed, the lighting segment of the threshold value display 30 becomes 1
When the threshold value Vth is increased by moving up the step, the setting direction switch 32a is set to the downward arrow position, and when the set switch 32b is pressed, the lighting segment of the threshold value display 30 moves down by one step. The threshold value Vth decreases.
The set switch 32b also serves as an input switch during teaching.

The output mode changeover switch 35 is also constituted by a slide switch. When the output mode changeover switch 35 is set to the L.ON (light-on) position, the output mode is switched on when the light receiving level Vs is higher than the threshold value Vth. ,
When set to the D.ON (dark ON) position, the mode is set to the ON output when the light receiving level Vs is lower than the threshold level Vth.

A signal for setting the threshold value Vth, a signal for switching the detection mode of the display unit 16,
Alternatively, a signal for switching between the detection mode and the threshold setting mode may be input to the signal processing unit 14 as an external signal.

Next, a method of using the photoelectric sensor 11 will be described. In the following description, it is assumed that the output mode switch 35 is set to the D.ON (dark ON) position. First, the case where the detection mode switch 33 is set to the normal mode (NORMAL) will be described. First, when the threshold value Vth is set in the teaching mode, the setting mode changeover switch 34 is set to the teaching mode (TEACH) position, the reference object is placed at the boundary between detection and non-detection, and the distance X1 to the reference object is set. = Vf / (Vr + βVf). When the set switch 32b is pressed in this state, the setting circuit 27 calculates a threshold value Vth0 from the acquired distance X1 at that time by the following equation (3), and obtains the acquired distance X1.
The threshold Vth0 is set and stored at a slightly shorter distance than the threshold Vth0. Vth0 = X1 · (1−α) (3) where α is a constant of 0 <α <1. When the threshold value Vth0 is set in the setting circuit 27 in this way, the corresponding display segment (for example, 30d) of the threshold value display 30 is turned on.

When the setting mode switch 34 is set to the adjustment mode (ADJ), the threshold setting switch 3
2, the threshold value Vth0 can be set. That is, when the set direction switch 32a is set to the upward arrow position and the set switch 32b is pressed, the set switch 3
Each time 2b is pressed, the threshold value Vth0 increases by a certain distance, and the lighting segment position of the threshold value indicator 30 moves upward. When the set direction switch 32a is set to the downward arrow position and the set switch 32b is pressed, each time the set switch 32b is pressed, the threshold value Vth0 is shortened by a fixed distance, and the lighting segment position of the threshold value display 30 is lowered. Move to.

After setting the threshold value Vth0 by any method, the setting mode changeover switch 34 is set to the operation mode (RU).
When switching to N), the threshold value Vth0 is fixed, and the lighting segment of the threshold value display 30 does not change even if the set switch 32b is operated. In this operation mode, the photoelectric sensor 11 measures the distance X to the object 18, and the distance to the object 18 (the length of the bar graph) displayed on the feature display 29 as a bar graph is the measured object. It changes according to the distance X to 18. The measurement distance X is compared with a threshold value Vth0 set in advance by the comparison circuit 25. If the measurement distance X is larger than the threshold value Vth0 (X
> Vth0), or in terms of display, the bar graph of the feature quantity display 29 is changed to the threshold display 30 as shown in FIG.
Exceeds the lighting segment (for example, 30d), the off signal is output from the comparison circuit 25, and the output indicator 31 is turned off. Conversely, when the measured distance X is smaller than the threshold value Vth0 (X <Vth0), or in terms of display, the bar graph of the feature quantity display 29 is changed to the threshold display 30 as shown in FIG. If the lighting segment (for example, 30d) is not exceeded, an ON signal is output from the comparison circuit 25, and the output indicator 31 is turned on.

Next, the case where the detection mode is set to the zone mode will be described. Detection mode switch 3
3 is set to the zone mode (ZONE), and the setting mode changeover switch 34 is set to the teaching mode (TEAC).
If H) is set, the reference object is placed at the center of the detection zone, and the distance X2 = Vf / (Vr + βVf) to the reference object is measured. In this state, when the set switch 32b is pressed, the setting circuit 27 calculates the lower limit value Vth1 from the acquired distance X2 at that time by the following equation (4), and sets the lower limit value Vth1 to a shorter distance than the acquired distance X2. Remember. Vth1 = X2 · (1−α) (4) Subsequently, the setting circuit 27 calculates the upper limit value Vth2 from the acquired distance X2 by the following equation (5), and sets the upper limit value Vth2 to a longer distance than the acquired distance X2. Set and memorize. Vth2 = X2 · (1 + α) (5) Again, α is a constant of 0 <α <1.
The values of α used in the expressions (4) and (5) may be different from each other. In this way, the upper limit V
When the threshold value th2 and the lower limit value Vth1 are set, the corresponding two display segments (for example, 30
c, 30e) light up.

When the detection mode changeover switch 33 is set to the zone mode (ZONE) and the setting mode changeover switch 34 is set to the adjustment mode (ADJ), the upper limit value Vth2 and the lower limit value of the detection zone are set by the threshold value setting switch 32. The value Vth1 can be set. That is, when the set direction switch 32a is set to the upward arrow position and the set switch 32b is pressed, each time the set switch 32b is pressed, the range between the upper limit value Vth2 and the lower limit value Vth1 expands, and the upper limit value Vth is increased.
The lighting segment position of the threshold value display 30 indicating th2 moves upward, and the lighting segment position of the threshold value display 30 indicating the lower limit value Vth1 moves downward. Also,
When the set direction switch 32a is set to the downward arrow position and the set switch 32b is pressed, the set switch 32b is pressed.
Each time is pressed, the distance between the upper limit value Vth2 and the lower limit value Vth1 becomes narrower, the lighting segment position of the threshold value display 30 indicating the upper limit value Vth2 moves downward, and the threshold value display 30 indicating the lower limit value Vth1 is changed. The lighting segment position moves upward.

After setting the upper limit value Vth2 and the lower limit value Vth1 by any method, when the setting mode changeover switch 34 is switched to the operation mode (RUN), the upper limit value Vth2 and the lower limit value Vth1 are fixed, and the set switch 32b is operated. However, the lighting segment of the threshold value display 30 does not change. In this operation mode, the photoelectric sensor 11 measures the distance X to the object 18, and only one feature quantity display 29 may be used (if it is desired to display an intermediate value, two may be turned on). The position of the object 18 is displayed by lighting the display segments 29a, 29b,.
The position display by the lighting segments 29a, 29b,... Changes according to the position of the object 18. The measured distance X of the object 18 is equal to the upper limit V
When the object 18 is within the detection zone (Vth1 <X <Vth2), or in terms of display, the lighting segment of the feature amount display 29 (for example, FIG. 5) , 29d) is between the lighting segment (for example, 30e) set to the upper limit value and the lighting segment (for example, 30c) set to the lower limit value, an off signal is output from the comparison circuit 25, and the output signal is output. The indicator light 31 is turned off. Conversely, when the object 18 is outside the detection zone (X <Vth1 or Vth2 <X), or in terms of display, the lighting segment (for example, 29g) of the feature quantity display 29 as shown in FIG. Is the threshold indicator 3
Lighting segments set to the upper limit of 0 (for example,
30e), or a lighting segment (for example, 30 g) in which the lighting segment (for example, 29 g) of the feature amount display 29 is set to the lower limit of the threshold value display 30.
If it is lower than c), an ON signal is output from the comparison circuit 25, and the output indicator 31 is turned on.

Next, at the time of shipment from the factory, the photoelectric sensor 1
The threshold value stored in 1 (hereinafter referred to as a specific threshold value) will be described. The photoelectric sensor 11 is placed at a specified distance in front of the photoelectric sensor 11 at a manufacturing factory, and an object for setting a threshold value is taught in the above procedure. That is, in the normal mode, one threshold is set by teaching, and in the zone mode, two thresholds (upper limit and lower limit) are set by teaching. Here, in the case of the normal mode, the specific threshold value set at the time of factory shipment is a distance Xmax (maximum distance threshold value) corresponding to the maximum set distance (real space) shown in FIG. The distance Xmin (minimum distance threshold) corresponding to the distance (real space) or an arbitrarily selected intermediate value may be used. In the case of the zone mode, the arbitrarily selected two intermediate values are used.

However, the specific threshold value set by teaching at the time of shipment from the factory is stored in a location different from the threshold value used for teaching during actual use, and is written as a digital value in a nonvolatile memory such as an EEPROM. .
Therefore, the threshold value that is taught during actual use is deleted when a new teaching or new threshold value is set, while the specific threshold value set at the factory is newly used during actual use. It is not erased even if the threshold value is set or a new threshold value is set.

When the specific threshold value set at the time of shipment from the factory is used, all photoelectric sensors 11 can be set to the same threshold value by a simple operation. For example, when the detection mode switch 33 is set to the normal mode (NORMAL), the setting mode switch 34 is set to the teaching mode (TEAC).
When the set switch 32b is pressed in accordance with H), the input time measuring circuit 28 starts to measure the time during which the set switch 32b is pressed. When the time during which the set switch 32b is pressed is shorter than a predetermined time (for example, 3 seconds), the normal teaching operation as described above is performed, and the distance to the object placed in front of the photoelectric sensor is threshold. Set as a value.

On the other hand, when the input time measuring circuit counts up while the set switch 32b is pressed for longer than the predetermined time, the specific threshold value stored in the nonvolatile memory (the threshold value at the time of shipment from the factory) is stored. Is read out and set in the setting circuit 27 as a threshold value, and the corresponding display segment of the threshold value display 30 is turned on. As the value of this specific threshold value, the same value is stored for all photoelectric sensors 11 having the same product number, so that all the photoelectric sensors 11 can be easily set to the same threshold value by such an input operation. can do. Further, the specific threshold value is obtained by placing an object at a specified distance at the time of shipment from the factory and memorizing the same, so that it is absolutely accurate.

In particular, in the distance setting type photoelectric switch, teaching cannot be performed so as to be the minimum setting distance. However, in the photoelectric sensor 11, a minimum distance threshold value corresponding to the minimum setting distance is stored in advance at the time of factory shipment. Can be easily set to the minimum distance threshold value. Specified threshold set at the time of shipment from the factory (threshold for minimum distance)
Then, it is easy to set the hysteresis (the hysteresis of the threshold value when the object moves from a side closer to the far side than the threshold value and the hysteresis of the threshold value when the object moves from the far side to the closer side) easily. become. Also, if it is possible to set the maximum distance threshold and the minimum threshold stored at the time of shipment from the factory, the threshold can be set to the maximum setting distance and the minimum setting distance without considering the state of the detected object. It can be set freely.

When a threshold is set according to the distance of an object placed in front in a normal teaching mode, immediately after teaching, as shown in FIG. 3 or FIG. 30 is the central display segment 30
Although d lights up, when a threshold value is set by a specific threshold value set at the time of factory shipment, a display segment corresponding to the value of the specific threshold value is lit. For example, when the maximum distance threshold value stored at the time of shipment from the factory is set, the uppermost display segment 30g is turned on as shown in FIG. When the threshold value is set, the lowermost display segment 30a is turned on as shown in FIG. Immediately after teaching, the display mode of the threshold value indicator 30 changes depending on the setting method of the threshold value, so that it is possible to see at a glance which setting method has been set, and whether the maximum distance threshold value has been set or not. It is also clear at a glance whether the distance threshold has been set.

When the detection mode switch 33 is set to the zone mode (ZONE), the setting mode switch 34 is set to the teaching mode (TEAC).
When the set switch 32b is pressed in accordance with H), the input time measuring circuit 28 starts to measure the time during which the set switch 32b is pressed. When the time during which the set switch 32b is pressed is shorter than a predetermined time (for example, 3 seconds), the normal teaching operation in the zone mode is performed as described above, and the distance to the object placed in front of the photoelectric sensor is determined. The upper and lower limits are set based on

On the other hand, when the time during which the set switch 32b is pressed is longer than the predetermined time and the input time measuring circuit counts up, the two specific threshold values (upper limit value, lower limit value) stored in the nonvolatile memory are stored. Value) is read and set in the setting circuit 27 as an upper limit value and a lower limit value,
The corresponding two display segments of the threshold indicator 30 light up. As for the upper limit value and the lower limit value, the same value is stored for each photoelectric sensor 11 of the same product number, so that such an input operation makes it easy and accurate to set all photoelectric sensors 11 to the detection zone. Can be set to

When a large number of photoelectric sensors are used on the same line, the set distance (threshold) of all photoelectric sensors is used.
Are often set the same. In that case, in the photoelectric sensor 11 of the present invention, it is not necessary to adjust the threshold value of each photoelectric sensor 11 so that the same threshold value is set for each setting object. Threshold setting time can be greatly reduced.

Further, in the photoelectric sensor 11, a plurality of specific thresholds are stored at the time of shipment from the factory according to the set resolution, and an arbitrary value among the plurality of specific thresholds is stored at the time of actual use. Alternatively, the threshold value can be set by the photoelectric sensor 11. As the plurality of specific thresholds, for example, values obtained by equally dividing the minimum distance threshold and the maximum distance threshold may be stored in the nonvolatile memory as the specific thresholds, respectively, or A value selected at random may be stored in the nonvolatile memory as a specific threshold value.

When teaching and storing a plurality of specific threshold values at the time of shipment from the factory as described above, the level selection circuit 36 is used. That is, data (for example, a threshold level number) for identifying a specific threshold is input from the level setting circuit 36 by a switch operation, an external signal input, or the like, and each specific threshold is stored together with the identification data in a nonvolatile manner. It is stored in the memory. Then, at the time of actual use, the photoelectric sensor 11 is set to the teaching mode,
When identification data indicating a specific threshold to be set is input to the level setting circuit 36 and the set switch 32b is pressed for a predetermined time or more, a specific threshold specified by the identification data among a plurality of specific thresholds is set. Is read from the non-volatile memory and set in the setting circuit 27.

Here, a case where a plurality of specific threshold values are handled in the case of the normal mode has been described, but the same applies to a case where a plurality of sets of specific threshold values (upper limit value, lower limit value) are handled in the zone mode.

Next, a description will be given of a setting method in a case where it is necessary to adjust the threshold value of the plurality of photoelectric sensors 11 to a value other than the specific threshold value stored in the nonvolatile memory. The photoelectric sensor 11 has a threshold value output unit 37 for outputting a set threshold value. The threshold output unit 37 or a display panel connected to the threshold output unit 37 can digitally display the threshold set by the teaching or threshold setting switch 32. .

When it is desired to equalize the threshold values of the plurality of photoelectric sensors 11, the threshold values of the photoelectric sensors 11 are taught or the threshold setting switch 32 is used.
The threshold value set by the threshold value output unit 37 is checked each time. In this way, the threshold value of each photoelectric sensor 11 is set to the same value by trial and error. In this method, the time and effort are increased, but it is possible to accurately set the value to an arbitrary set value.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
An embodiment will be described. First, the equation (1) will be described in detail. FIG. 10 shows a light emitting / receiving optical system of the photoelectric sensor. Reference numeral 41 denotes a light projecting lens system of the light projecting unit 12, 21 denotes a light receiving lens system of the light receiving unit 13, 22 denotes a position detecting element, and 42 denotes a sensor end face. An axis is determined, and the Y axis is determined so as to coincide with the surface of the position detection element 22. Here, the distance between the surface of the position detecting element 22 and the main surface of the light projecting lens system 41 is D,
Let Xd be the distance between the main surface of No. 1 and the sensor end face 42 and x be the distance from the sensor end face 42 to the object 18 on the X axis. The distance between the optical axis (X axis) of the light projecting lens system 41 and the optical axis A of the light receiving lens system 21 is K, and the position detecting element 22
S is the distance between the center O of the light-receiving lens system 21 and the optical axis A of the light-receiving lens system 21. Further, let Xo be the distance in the X-axis direction of the object point on the X-axis formed at the center O of the position detection element 22 from the sensor end face 42, and set the object 1 at the distance x from the sensor end face 42 on the X-axis.
The y-axis position (distance measured from the center O of the position detection element 22) of the light spot where the light reflected by 8 forms an image on the position detection element 22 is defined as y.

As is apparent from the geometrical relationship shown in FIG. 10, there is a relationship between these values as expressed by the following equations (6) and (7).

[0063]

(Equation 1)

This equation (6) can be rearranged into the following equation (8).
Equation (7) becomes the following equation (9). Then, the expression (10) is obtained by eliminating Xd from the expressions (8) and (9).

[0065]

(Equation 2)

[0066] As shown in FIG. 11, the light spot is focused on a point of the distance y the length of the light receiving surface from the center O of the position detecting element 22 of the L, the photocurrent I _A flows to one terminal and the other When the photocurrent I _B to the terminal flows, as is well known, the light receiving position y is represented by the following equation (11).

[0067]

(Equation 3)

When this equation (11) is substituted into 1 / (S−y) and rearranged, it can be written as the following equation (12). However, (S−L) / (S + L) = β (linearity correction coefficient).

[0069]

(Equation 4)

Therefore, when the equation (12) is substituted into the equation (10), the distance x to the object is as shown in the following equation (13).

[0071]

(Equation 5)

Here, the offset constant P and the span constant Q
Is defined as the following equation, the above equation (1) is obtained.

[0073]

(Equation 6)

Although the basis of the equation (1) has been clarified, the distance X is equivalent to the distance to the object X = Vf / (Vr + βVf)... 16) Consider In the photoelectric sensor 11, Expression (16) is used as distance information.

The parameter β included in the above equation (16)
Varies depending on the arrangement and dimensions of the optical system of the photoelectric sensor, and therefore, variation tends to occur. However, as the value of the parameter β used for calculating the distance X from the light receiving signals Vf and Vr by the equation (16), a value βi calculated on the assumption that there is no error in the arrangement and dimensions of the optical system is used. Used. Therefore, the actual parameter β of the photoelectric sensor and (1
There is a variation between the ideal value βi used in the calculation of the expression (6) and the object is placed at a fixed distance, and
Even when the distance X calculated by the expression 6) was set as the threshold value, the threshold value of each photoelectric sensor varied.

In the embodiment described here, this parameter β is actually measured and corrected. FIG. 12 is a partially broken block diagram showing an electrical configuration of a photoelectric sensor 43 according to another embodiment of the present invention. The photoelectric sensor 43 includes a parameter correction circuit 44 that corrects the parameter β based on the light receiving signals Vf and Vr from the light receiving circuits 23f and 23r,
A threshold input unit 45 for inputting a threshold to be set as a digital value.

As a preparation, the object 18 is placed at a specified distance in front of the photoelectric sensor 43, and the distance when the ideal parameter βi calculated by the photoelectric sensor having no error in the arrangement and dimensions of the optical system is used. An ideal value Xi of X is obtained in advance.

Next, the object 18 is placed at the same distance in front of the photoelectric sensor 43, and the distance X is obtained. This photoelectric sensor 4
If the third parameter β is the ideal value βi, the value of the distance X should also be the ideal value Xi. However, since the parameter β actually varies, the distance X does not match the ideal value Xi. The parameter β is expressed by the following equation (17) according to the equation (16).

[0079]

(Equation 7)

However, since the distance X is not known, the actual parameter β cannot be obtained. Therefore, the parameter correction circuit 44 calculates the actual value of the parameter β back using the ideal value Xi of the distance X when the object 18 is placed at the specified position and the light receiving signals Vf and Vr, and stores it.
That is, the actual parameter β is obtained by the following equation (18) and stored.

[0081]

(Equation 8)

The photoelectric sensor 43 is shipped with the parameter β corrected at the time of shipment from the factory, and the arithmetic circuit 24 calculates the distance X using the corrected parameter β. The corrected parameter β is also used for setting the threshold value.
Therefore, the photoelectric sensor 43 is shipped without variation. Therefore, when setting the threshold value, there is no variation among the photoelectric sensors 43, and a common threshold value (specific threshold value) can be set.

Further, in the photoelectric sensor 43, the threshold value can be inputted as a digital value from the threshold value input section 45 in order to eliminate an error at the time of inputting the threshold value. Therefore, by inputting a common equal threshold value to each photoelectric switch 43, each photoelectric switch 43 can be set to a common threshold value and the setting state can be made the same.

(Third Embodiment) FIG. 13 is a partially cut-away block diagram showing a photoelectric sensor 51 according to still another embodiment of the present invention. 52 is a minimum light receiving amount setting unit, which is the total light receiving amount of the light receiving unit 13, that is, the light receiving circuit 23f,
23r, the sum of the light receiving signals Vf and Vr (Vf +
Vr), and monitors whether the total amount of received light is not less than the minimum amount of received light.

In the minimum light receiving amount setting section 52, the value of the minimum light receiving amount VL is preset at the time of factory shipment as follows. In other words, a detection object having the lowest reflected light amount (that is, having a limit reflectance) specified by the photoelectric sensor 51 is placed at the maximum detection distance specified by the rating of the photoelectric sensor 51, and the light reflected by the detection object is Received light amount VL = Vf +
Vr is sampled, and the value of the minimum light receiving amount (non-light incident level) VL is stored in the nonvolatile memory of the minimum light receiving amount setting section 52.

The minimum light receiving amount setting section 52 having the minimum light receiving amount set in this way always detects the total light receiving amount Vf + Vr, and does not perform the distance calculation when the total light receiving amount Vf + Vr is equal to or less than the minimum light receiving amount VL.

Therefore, the minimum light receiving amount setting unit 5 as described above
In the photoelectric sensor 51 having the minimum light receiving amount VL in the minimum light receiving amount setting unit 52 as described above, the light receiving amount range in which a normal distance calculation can be performed is accurately set. As described above, in any of the photoelectric sensors 51, the light receiving amount range is set accurately, and there is no variation between models. Therefore, if necessary, a plurality of photoelectric sensors are set to the same state equally. Therefore, by inputting a threshold value to the plurality of photoelectric sensors 51 from the threshold value input unit 45 as a digital value, each photoelectric sensor 51 can be set to the same state.

(Fourth Embodiment) FIG. 14 is a partially broken block diagram showing a photoelectric sensor 53 according to still another embodiment of the present invention. At the time of factory shipment, the maximum detection distance and the minimum detection distance are stored in the distance value range limiting circuit. That is, the object 18 is received in front of the photoelectric sensor 53 at the maximum set distance specified by the sensor rating, the distance is calculated from the amount of received light, and the distance is calculated as the maximum detection distance (X _U ). It is stored in the limiting circuit.
Also, the object 18 is received at a minimum set distance defined by the sensor rating in front of the photoelectric sensor 53, the distance is calculated from the amount of received light, and the distance is calculated as the minimum detection distance ( _XL ). It is stored in the limiting circuit.

In the normal detection operation of the photoelectric sensor 53, if the detection distance of the object is calculated as a result of calculating the detection distance of the object, the maximum detection distance (X _U ) is calculated as the distance calculation value. The minimum detection distance ( _XL ) is output as a distance calculation value when the output is smaller than the minimum detection distance.

In the photoelectric sensor 53, the distance can be set only within a sensor standard that can always perform a normal operation. Therefore,
For example, in the case of setting the maximum distance with a photoelectric sensor for which a threshold value is set by pressing a button, the same maximum distance can be set for all the photoelectric sensors. The same applies to the case where the minimum distance is set.

[Brief description of the drawings]

FIG. 1 is a front view of a photoelectric sensor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the photoelectric sensor according to the first embodiment.

FIG. 3 is a diagram showing a display state in a normal mode on a display unit of the photoelectric sensor according to the first embodiment.

FIG. 4 is a diagram showing another display state in a normal mode on the display unit of the photoelectric sensor according to the embodiment.

FIG. 5 is a diagram showing a display state in a zone mode on a display unit of the photoelectric sensor according to the first embodiment.

FIG. 6 is a diagram showing another display state in the zone mode on the display unit of the photoelectric sensor of the above.

FIG. 7 is a diagram illustrating a relationship between a detection distance and a calculation distance X in a real space.

FIG. 8 is a diagram illustrating a display state of a display unit in which a threshold is set to a maximum distance threshold.

FIG. 9 is a diagram illustrating a display state of a display unit in which a threshold is set to a minimum distance threshold.

FIG. 10 is a diagram showing various quantities used for obtaining an arithmetic expression representing a distance to an object.

FIG. 11 is a schematic diagram of a position detecting element.

FIG. 12 is a block diagram showing an electrical configuration of a photoelectric sensor according to another embodiment of the present invention.

FIG. 13 is a block diagram showing an electrical configuration of a photoelectric sensor according to still another embodiment of the present invention.

FIG. 14 is a block diagram showing an electrical configuration of a photoelectric sensor according to still another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 12 light emitting unit 13 light receiving unit 14 signal processing unit 24 arithmetic circuit 25 comparison circuit 27 setting circuit 28 input time measuring circuit 29 feature amount display 30 threshold display 32 threshold setting switch 32b set switch 34 setting mode switch 36 Level selection circuit 37 Threshold output section

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tatsuya Matsunaga 10F, Omron Co., Ltd. QQ23 QQ25 QQ27 SS12 2F112 AA06 AB03 BA06 CA12 DA05 DA25 DA26 EA03 FA03 FA07 FA21

Claims (7)

[Claims] 1. A distance to a target object or a physical quantity equivalent to the distance is calculated based on the principle of triangulation based on a light receiving position in the position detection element, and the distance or a physical quantity equivalent to the distance is compared with a threshold value. A photoelectric sensor having a function of determining a distance and a teaching function for setting the threshold value, the photoelectric sensor including input means for setting a specific threshold value by a predetermined operation. 2. The photoelectric sensor according to claim 1, wherein the specific threshold is a maximum distance threshold or a minimum distance threshold. 3. The photoelectric sensor according to claim 1, wherein a value that the specific threshold value can take is arbitrarily selected from discrete threshold values. 4. The photoelectric sensor according to claim 1, further comprising means for outputting a set threshold value. 5. The method for manufacturing a photoelectric sensor according to claim 2, wherein an object is placed at a specified maximum distance or minimum distance, and an actual measured value of a distance to the object at that time or a physical quantity equivalent thereto is set. A method for manufacturing a photoelectric sensor, wherein the method is stored as a value. 6. The method for manufacturing a photoelectric sensor according to claim 1, wherein parameters included in a relational expression relating a light receiving position of the position detecting element and a distance of the target object or a physical quantity equivalent thereto are measured and corrected. A method for manufacturing a photoelectric sensor, comprising: 7. The method for manufacturing a photoelectric sensor according to claim 1, wherein the non-light-incident determination level is measured and adjusted.