JP2013150158A - Photoelectric switch and sensitivity adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce variation of an individual photoelectric switch and implement an appropriate sensitivity adjustment without using such a component as a variable resistance.SOLUTION: When a threshold setting section 12 instructed by a threshold operation section 15 on a usage stage changes a threshold stored in a threshold holding section 11, if a new threshold incremented/decremented in response to the instruction is lower than a lower limit value determined so as to reduce variation of a photoelectric switch 1 on a manufacturing stage, the lower limit value is set as a new threshold in the threshold holding section 11.

Description

  The present invention relates to a photoelectric switch and a sensitivity adjustment method capable of setting sensitivity so as to reduce variation among products.

The photoelectric switch has variations in a light projecting element, a light receiving element, a processing circuit that converts a received optical signal into a voltage amplitude, and the like. For this reason, the light receiving level of the photoelectric switch varies.
Usually, in the photoelectric switch, the circuit gain is determined so that the product specification is sufficient for the solid having the smallest variation. Assuming that the variation of the light projecting element is 3 times, the variation of the light receiving element is 1.5 times, the variation of the processing circuit is 2 times, and the total variation is 9 times, the photoelectric switch with the largest variation is the largest. The margin is nine times the margin required for the small photoelectric switch. As described above, when the margin is excessive, there is a problem that the possibility of operating with a noise signal other than the original received light signal increases.

  Therefore, some photoelectric switches are provided with a variable resistor for sensitivity adjustment (see, for example, Patent Document 1), and the circuit gain is optimized for each photoelectric switch so as to obtain an appropriate margin. . This prevented an excessive margin setting.

  In addition, for example, at the manufacturing stage, the light emitting efficiency of each light projecting element is measured, and an optimum resistance value is determined for each photoelectric switch so as to obtain a circuit gain according to the measurement result. It was implemented. This can also prevent an excessive margin setting.

Japanese Utility Model Publication No. 7-25624

  Since the conventional photoelectric switch is configured as described above, when a variable resistor for optimizing the circuit gain is used, the rotation angle of the variable resistor and the sensitivity are roughly proportional, so in the case of an excessive margin There was a problem that fine adjustment of sensitivity became difficult. There is also a problem of hindering miniaturization due to the necessity of parts such as a variable resistor.

  The present invention has been made to solve the above-described problems, and provides a photoelectric switch and a sensitivity adjustment method for performing appropriate sensitivity adjustment while reducing variations among photoelectric switches without using components such as variable resistors. It aims to be realized.

  According to a first aspect of the present invention, there is provided a photoelectric switch that projects light of a light amount corresponding to a light projecting current onto a detection region, and receives light from the light projecting unit, and has a level corresponding to the amount of received light. A light receiving unit that outputs a light receiving signal, a light receiving signal output from the light receiving unit, and a comparison unit that determines the presence or absence of an object in the detection area by comparing the light receiving signal with a predetermined threshold, and an instruction to increase or decrease the threshold from the outside A threshold value operating unit and a lower limit value of the threshold value set based on the light receiving signal level output from the light receiving unit in the manufacturing process. In response to an instruction from the threshold value operating unit, the threshold value is increased or decreased to set a new threshold value. In this case, a threshold value setting unit is provided that sets a new threshold value according to an instruction when the threshold value is equal to or greater than the lower limit value, and sets the lower limit value as a new threshold value when the threshold value becomes smaller than the lower limit value.

  According to a second aspect of the present invention, there is provided a photoelectric switch that projects light of a light amount corresponding to a light projecting current to a detection region, and receives light from the light projecting unit, and has a level corresponding to the amount of received light. A light receiving unit that outputs a light reception signal, a light projecting current operating unit that receives an instruction to increase or decrease the light projecting current of the light projecting unit from the outside, and an instruction from the light projecting current operating unit that are supplied to the light projecting unit A light projecting control unit that changes the light projecting current; and a comparison unit that compares the light reception signal output from the light receiving unit with a predetermined threshold value to determine the presence or absence of an object in the detection region. Is set based on the light reception signal level output by the light receiving unit.

  According to a third aspect of the present invention, there is provided a photoelectric switch for projecting light of a light amount corresponding to a light projecting current to a detection region, receiving light from the light projecting unit, and having a level corresponding to the amount of received light. A light receiving unit that outputs a light reception signal, a comparison unit that compares the light reception signal output from the light reception unit with a predetermined threshold and determines the presence or absence of an object in the detection region, and an instruction to increase or decrease the light projection current from the outside And an upper limit value of the light projecting current set based on the light receiving signal level output from the light receiving unit in the manufacturing process. Upon receiving an instruction from the light projecting current operating unit, the light projecting unit When increasing or decreasing the projection current supplied to the projector, if the projection current is less than or equal to the upper limit value, a new projection current is set according to the instruction, and when the projection current becomes greater than the upper limit value, the upper limit value is And a light projection control unit for setting the light projection current.

  According to a fourth aspect of the present invention, there is provided a photoelectric switch for projecting light of a light amount corresponding to a light projection current to a detection region, receiving light from the light projecting unit, and having a level corresponding to the amount of received light. A light receiving unit that outputs a light reception signal, a comparison unit that compares the light reception signal output from the light reception unit with a predetermined threshold and determines the presence or absence of an object in the detection region, and a threshold that the comparison unit uses for determination from the outside A threshold value operating unit that receives an instruction to increase or decrease the threshold value, and a threshold value setting unit that receives an instruction from the threshold value operating unit and changes a threshold value used in the comparison unit. Is set on the basis of the received light signal level.

  According to a fifth aspect of the present invention, there is provided a photoelectric switch that projects light of a light amount corresponding to a light projecting current onto a detection region, and receives light from the light projecting unit and has a level corresponding to the amount of received light. A light receiving unit that outputs a light reception signal, a gain operation unit that receives an instruction to increase or decrease the gain when the light reception unit converts the amount of received light into a light reception signal, and an instruction from the gain operation unit A gain control unit that changes the gain, and a comparison unit that compares a light reception signal output from the light receiving unit with a predetermined threshold to determine the presence or absence of an object in the detection region. Is set on the basis of the received light signal level.

  According to a sixth aspect of the present invention, there is provided a photoelectric switch for projecting light of a light amount corresponding to a light projection current to a detection region, receiving light from the light projecting unit, and having a level corresponding to the amount of received light. A light receiving unit that outputs a light reception signal, a gain operation unit that receives an instruction to increase or decrease the gain when the light reception unit converts the amount of received light into a light reception signal, and an instruction from the gain operation unit A gain control unit that changes the gain, and a comparison unit that compares the light reception signal output from the light receiving unit with a predetermined threshold to determine the presence or absence of an object in the detection region, and the light projecting current of the light projecting unit is And is set based on the received light signal level output by the light receiving unit in the manufacturing process

  The sensitivity adjustment method according to claim 7 of the present invention has a lower limit value of the threshold value set based on the light reception signal level output from the light receiving unit in the manufacturing process, and is increased or decreased according to an instruction received from the threshold value operation unit. When the threshold value is equal to or greater than the lower limit value, the threshold value is set as a new threshold value. When the threshold value increased or decreased according to an instruction received from the threshold value operation unit is smaller than the lower limit value, the lower limit value is set as a new threshold value. It is what I did.

  The sensitivity adjustment method according to claim 8 of the present invention has an upper limit value of the light projection current set based on the light reception signal level output from the light receiving unit in the manufacturing process, and receives an instruction received from the light projection current operation unit. If the projected current increased or decreased in response to the upper limit value or less, the projected current is set to a new projected current, and the projected current increased or decreased in response to an instruction received from the projected current operation unit. If it is larger, the upper limit value is set to a new light projection current.

  According to this invention, since the lower limit value of the threshold according to the variation for each product is determined in the manufacturing stage, and the sensitivity is adjusted by changing the threshold value in the range of the lower limit value or more in the use stage, It is possible to reduce variations among photoelectric switches and perform appropriate sensitivity adjustment. Moreover, it is not necessary to use components such as variable resistors for circuit gain optimization.

  According to the present invention, the upper limit value of the projection current corresponding to the variation of the projection element is determined in the manufacturing stage, and the sensitivity adjustment is performed by changing the projection current within the range of the upper limit value or less in the use stage. Since it did in this way, the dispersion | variation for every photoelectric switch can be reduced, and appropriate sensitivity adjustment can be performed. Moreover, it is not necessary to use components such as variable resistors for circuit gain optimization.

It is a block diagram which shows the structure of the photoelectric switch which concerns on Embodiment 1 of this invention. 4 is a graph showing a relationship between a distance and a light reception signal level in the reflector type photoelectric switch according to the first embodiment. 4 is a flowchart illustrating a lower limit threshold setting mode in the manufacturing stage of the photoelectric switch according to the first embodiment. 4 is a flowchart illustrating a threshold setting mode by a user operation of the photoelectric switch according to the first embodiment. It is a block diagram which shows the structure of the photoelectric switch which concerns on Embodiment 2 of this invention. 6 is a block diagram illustrating a modification of the photoelectric switch according to Embodiment 2. FIG.

Embodiment 1 FIG.
As shown in FIG. 1, the photoelectric switch 1 according to the first embodiment includes a light projecting drive unit 2, a light projecting element 3, and a light projecting unit as a light projecting unit for projecting light toward a detection region where an object exists. An optical lens 4 is provided. In addition, a light receiving lens 5 and a light receiving element 6 are provided as a light receiving unit for receiving light from the direction of the detection region. The optical signal received by the light receiving element 6 is converted into a voltage signal by the signal processing unit 7 and amplified, and input to the control unit 8 as a light receiving signal. The light projecting element 3 is, for example, an LED (light emitting diode), and the light receiving element 6 is, for example, a photodiode.

The control unit 8 is composed of a microcomputer, and a program (firmware or the like) describing the processing contents of the light projection control unit 9, the comparison unit 10, and the threshold setting unit 12 is stored in a memory, and the microcomputer processor is stored in the memory. Execute the stored program. When the signal processing unit 7, the light projection control unit 9, and the comparison unit 10 need to be synchronized, the clock signal of the microcomputer is used as the synchronization signal.
Or you may comprise the control part 8 by a wired logic. Moreover, you may comprise partially with an analog circuit.

  The light projection control unit 9 controls the light projection current supplied from the light projection driving unit 2 to the light projecting element 3. The comparison unit 10 compares the light reception signal level input from the signal processing unit 7 with the threshold value held by the threshold value holding unit 11, and if the light reception signal level is higher (or lower) than the threshold value, there is an object. Then, the detection result is output to the output unit 13. Whether the output is turned on when the received light signal level is higher than the threshold (so-called light on) or the output is turned on when the received light signal level is lower than the threshold (so-called dark on) is not shown. Hereinafter, the user may be able to select by SW) or the like.

  The threshold setting unit 12 generates and sets a threshold in the threshold holding unit 11. The mode switching operation unit 14 is a switch that switches between a threshold setting mode for setting a threshold and a detection mode for detecting the presence or absence of an object in accordance with a user operation. Here, when the threshold selection mode is selected, the mode switching operation unit 14 instructs the threshold setting unit 12 to execute the threshold setting operation. Conversely, the threshold setting unit 12 operates during the period in which the detection mode is selected. Instead, the detection operation by the comparison unit 10 is performed.

Further, the threshold value operation unit 15 includes a switch that outputs a signal according to a user operation, and the threshold value setting unit 12 increases or decreases the threshold value held by the threshold value holding unit 11 by an amount corresponding to the output signal. That is, the user can adjust the sensitivity of the photoelectric switch 1 by operating the threshold value operation unit 15 to change the threshold value. Details of this will be described later.
Note that the mode switching operation unit 14 and the threshold value operation unit 15 may share one operation unit.

  Since the photoelectric switch 1 has variations in the light projecting element 3, the light receiving element 6, the signal processing unit 7, and the like as described above, the light reception signal level input to the comparison unit 10 varies for each product. . In view of this, a threshold value that reduces variations among products is set in the threshold value holding unit 11 at the manufacturing stage.

Here, a specific example of the threshold setting mode in the manufacturing stage will be described.
FIG. 2 is a graph showing the relationship between the distance and the received light signal level in the reflector type photoelectric switch 1. The horizontal axis of the graph represents the distance from the photoelectric switch 1, and the vertical axis represents the voltage level of the received light signal output from the signal processing unit 7. In this example, a reflector is installed at a distance of 5 m from the photoelectric switch 1 and the detection area is set between them. The light output from the photoelectric switch 1 is reflected by the reflector and output when the object blocks the optical path returning to the photoelectric switch 1. Is assumed to be on (dark on) or off (light on).

Here, as shown in FIG. 2A, the light reception signal level when the reflector is located at a position 5 m away from the photoelectric switch 1 is defined as a reference value A.
Further, under the conditions, as the reference values B and C used for setting the threshold, the peak value of the light reception signal level of the light reflected by the mirror (B shown in FIG. 2) and the peak of the light reception signal level of the light reflected by the white paper A value (C shown in FIG. 2) is obtained in advance.
Further, a reference position from the reference target and the photoelectric switch 1 is determined in advance so that the light reception signal level D satisfies A>D> B and A>D> C. The light reception signal level D of the reference target satisfies A>D> B and A>D> C regardless of the variations of the light projecting element 3, the light receiving element 6, the signal processing unit 7, and the like. Here, the reference position is set to a value corresponding to the position of 0.3 m from the photoelectric switch 1.

  FIG. 3 is a flowchart for setting the lower limit of the threshold in the manufacturing stage. When the mode switching operation unit 14 is switched to the lower threshold setting mode with the reference target installed at the reference position 0.3 m from the photoelectric switch 1 in the manufacturing stage (step ST1), the light receiving unit is reflected by the reference target. Light is received and converted into a received light signal by the signal processing unit 7, and the threshold setting unit 12 acquires the received light signal level D (step ST2).

Then, the threshold setting unit 12 stores the received light signal level D in the threshold holding unit 11 as the lower limit value _DL of the threshold (step ST4).

If the received light signal level varies by a factor of 1.5 due to variations in the light projecting element 3, the light receiving element 6, the signal processing unit 7, etc., as shown in FIG. The value is doubled, and the relative magnitude relationship does not change. Therefore, an appropriate lower limit value D _L can be set even if there is variation in the photoelectric switch 1.

In the above description, the threshold setting unit 12 directly sets the light reception signal level D of the reference target to the lower limit value D _L of the threshold. However, the present invention is not limited to this. For example, D _L = D × x (x is an arbitrary value) The value (D ′) based on the received light signal level D, such as the value of (), may be calculated (step ST3).
Moreover, the threshold value setting method described above is an example in the case of the reflector type photoelectric switch 1, and the threshold value setting method is not limited to this.

Next, a specific example of the threshold setting mode by the user will be described.
When the threshold value is adjusted by setting the threshold value by the threshold value setting unit 12 or by adjusting the threshold value through the threshold value operation unit 15, if the threshold value is lowered (that is, if the sensitivity is increased), a longer distance can be set as the detection region, but the threshold value is excessively lowered. (That is, if the sensitivity is increased too much), the light received by the light projecting element 3 in the case of the photoelectric switch 1 is detected by the light receiving element 6. Incorrect detection due to noise signals is caused.
On the other hand, if the threshold value is raised (that is, if the sensitivity is lowered), the detection area becomes shorter, but false detection can be reduced. As described above, if the sensitivity is increased too much, the possibility of erroneous detection increases, so the sensitivity cannot be increased indiscriminately.
Therefore, it is impossible to change the threshold value to be lower than the lower limit value of the threshold value that is set in the manufacturing stage and is appropriate for each photoelectric switch 1.

FIG. 4 is a flowchart in which the user adjusts the threshold value. When the user switches the mode switching operation unit 14 to the threshold setting mode, the threshold setting unit 12 receives an instruction from the mode switching operation unit 14 (step ST11), and obtains the received light signal level E from the signal processing unit 7 at that time. (Step ST12).
The threshold value setting unit 12 calculates a value E calculated by performing a predetermined calculation (for example, multiplying a predetermined ratio: 80% or adding or subtracting a predetermined value as a margin) to the received light signal level E. 'was a candidate for the new threshold value (step ST13), which, compared to the lower limit D _L threshold that is stored in advance in the threshold holding unit 11 (step ST14), the received light signal level E' is a lower limit value D If it is _L or more (step ST14 “YES”), the threshold setting unit 12 sets the received light signal level E ′ to the threshold D _TH and stores it in the threshold holding unit 11 (step ST15). On the other hand, when the received light signal level E ′ is smaller than the lower limit value D _L (step ST14 “NO”), the threshold value setting unit 12 sets the lower limit value D _L to the threshold value D _TH and stores it in the threshold value holding unit 11 (step ST16). ).

  As a result, it is possible to prevent the threshold value from being changed to an excessively low threshold value, and thus it is possible to prevent erroneous detection due to an excessive increase in sensitivity.

If the received light signal level E ′ is smaller than the lower limit value D _L (step ST14 “NO”), the threshold value setting unit 12 does not set the lower limit value D _L to the threshold value D _TH and store it in the threshold value holding unit 11. Therefore, the threshold adjustment may not be performed because it is determined that the threshold adjustment is impossible. In this case, it is preferable to make the user recognize by error display or the like that threshold adjustment has not been performed.

When the user increases or decreases the threshold value by pressing the threshold value operation unit 15, for example, every time the switch for increasing the threshold value (that is, lowering the sensitivity) of the threshold value operation unit 15 is pressed once, the threshold value operation unit 15 sets the threshold value. A high level output signal is output to the setting unit 12. Conversely, every time the switch for lowering the threshold (that is, increasing the sensitivity) is pressed once, a low level output signal is sent from the threshold operating unit 15 to the threshold setting unit 12. It will output. In this case, the threshold value setting unit 12 increases or decreases the threshold value held by the threshold value holding unit 11 according to the number of high level or low level output signals of the threshold value operation unit 15. In this case, the threshold setting unit 12 is increased or decreased the threshold in the range of above the lower limit D _L set in the threshold holder 11 in advance, not reduced more threshold if less than the lower limit D _L.

  As a result, as described above, it is possible to prevent the threshold value from being changed to an excessively low threshold value, and thus it is possible to prevent erroneous detection due to an excessive increase in sensitivity.

As described above, according to the first embodiment, the photoelectric switch 1 has a light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region, and receives light from the light projecting unit according to the amount of light received. levels and a light receiving unit that outputs a light reception signal of, and the light receiving signal receiving unit outputs is compared with a threshold value D _TH, the comparison unit 10 determines the presence or absence of an object in the detection area, the threshold D _TH from the outside A threshold value operating unit 15 that receives an instruction to increase or decrease, a threshold value holding unit 11 that holds a lower limit value D _L and a threshold value D _TH of a threshold value set based on a received light signal level D output from the light receiving unit in the manufacturing process, and a threshold value operation When the threshold value D _TH is increased or decreased in response to an instruction from the unit 15 and a new threshold value D _TH is set, if the threshold value D _TH is equal to or greater than the lower limit value D _L , a new threshold value D _TH corresponding to the instruction is set. D _TH is smaller than the lower limit D _L If you set the lower limit D _L in the new threshold D _TH And configured to include a threshold setting unit 12. For this reason, the threshold value corresponding to the variation characteristic for each photoelectric switch can be set in the manufacturing stage, so that variation can be reduced. In addition, even if the user changes the threshold value at the use stage, the new threshold value is set so as not to be smaller than the lower limit value obtained at the manufacturing stage. Can prevent false detection. Further, since the lower limit D _L in the threshold is set by the control unit 8 executes the program, can be part of such a conventional kind of variable resistor is not required, miniaturization of the photoelectric switch.

In the first embodiment, the threshold value can be changed by the user at the use stage. However, the present invention is not limited to this, and the threshold value may not be changed from the threshold value set at the manufacturing stage. Even in this configuration, since an appropriate threshold value is set according to the variation characteristic for each photoelectric switch in the manufacturing stage, it is not excessive sensitivity and erroneous detection can be prevented.
Further, the reception signal level D from the reference target may be acquired in a state where either one or both of the light projecting lens 4 and the light receiving lens 5 are absent.

Embodiment 2. FIG.
In the first embodiment, the threshold value when the user changes the threshold value and the lower limit value (corresponding to the upper sensitivity limit) are set according to each photoelectric switch 1, but the present invention is not limited to this. You may comprise so that the light projection current of the optical element 3 and its upper limit (equivalent to a sensitivity upper limit) may be set according to each photoelectric switch 1.

FIG. 5 is a block diagram illustrating a main configuration of the photoelectric switch 1 according to the second embodiment. The photoelectric switch 1 newly includes a light projection current operation unit 20, a current control value setting unit 21, and a current control value holding unit. 22, the threshold value setting unit 12 and the threshold value operation unit 15 shown in FIG. The other configuration is the same as that of the photoelectric switch 1 shown in FIG.
Since there is an individual difference in the light emission efficiency of the light projecting element 3, even if the light projecting current output from the light projecting drive unit 2 to the light projecting element 3 is set to the rated value, the light projecting amount is not always the same. Further, the characteristics of the light receiving element 6 and the signal processing unit 7 also vary. Therefore, in the second embodiment, at the manufacturing stage, the control unit 8 is configured to reduce the variation including any or all of the light projecting element 3, the light receiving element 6, and the signal processing unit 7 for each product. An upper limit value of the current control value output by the light projection control unit 9 is set in the current control value holding unit 22.

  For example, in the manufacturing stage, a predetermined reference signal corresponding to a rated current value or the like is given to the light projecting drive unit 2 to measure the signal level of the signal processing unit 7. Then, the degree of variation in the signal level of the signal processing unit 7 from the reference projection amount corresponding to the reference signal is obtained, and the current control value is corrected according to the degree of variation. Then, the current control value whose variation has been corrected is set in the current control value holding unit 22. In the detection mode, the light projecting drive unit 2 supplies a light projecting current having a level corresponding to the current control value input from the light projecting control unit 9 to the light projecting element 3. Thereby, the dispersion | variation for every product can be reduced.

  As described in the first embodiment, if the sensitivity is excessive, the photoelectric switch 1 may malfunction. Therefore, a light projection current corresponding to an appropriate sensitivity upper limit value that does not cause malfunction is determined and set in the current control value holding unit 22 as an upper limit value of the light projection current (current control value).

  Next, a case where the user performs sensitivity adjustment by operating the light projection current operation unit 20 to increase or decrease the light projection amount of the light projecting element 3 will be described. As with the threshold value operating unit 15 of the first embodiment, for example, each time the switch for increasing the light projecting current (that is, increasing the sensitivity) of the light projecting current operating unit 20 is pressed once, the light projecting current operating unit 20 Each time the switch for lowering the projection current (that is, lowering the sensitivity) is pressed once, a high level output signal is output from the projection current operation unit 20 to the projection control unit 9. A low level output signal is output to 9. In this case, the light projecting control unit 9 increases or decreases the current control value set in the light projecting control unit 9 according to the number of high level or low level output signals of the light projecting current operation unit 20. At this time, the light projection control unit 9 increases or decreases the current control value in a range that is equal to or less than a preset upper limit value of the projection current, but does not increase the current control value beyond that when the upper limit value is exceeded.

  As a result, it is possible to prevent the amount of light emitted from being excessively increased due to an excessively high light projecting current, and thus it is possible to prevent erroneous detection due to an excessive increase in sensitivity.

  As described above, according to the second embodiment, the photoelectric switch 1 receives the light from the light projecting unit and the light projecting unit that projects the amount of light corresponding to the light projecting current to the detection region, and sets the amount of received light. A light receiving unit that outputs a light receiving signal of a corresponding level, a light receiving signal that is output from the light receiving unit are compared with a threshold value DTH, and a comparison unit 10 that determines the presence or absence of an object in the detection region; A projection current operating unit 20 that receives an instruction to increase or decrease, a projection control current control value that is set based on the signal level of the signal processing unit 7 in the manufacturing process, and an upper limit value thereof are stored. When increasing or decreasing the light projection current supplied to the light projection unit in response to an instruction from the operation unit 20, if the current control value is less than or equal to the upper limit value, a new current control value is set according to the instruction, and the current control value is When the value is larger than the value, the light projection control unit 9 sets the upper limit value to a new current control value. It was configured to include. For this reason, since the current control value according to the variation characteristic for each photoelectric switch can be set in the manufacturing stage, variation can be reduced. In addition, even if the user changes the amount of light emitted at the usage stage, the new current control value is set so as not to be larger than the upper limit value obtained at the manufacturing stage. It is possible to prevent erroneous detection due to excessive increase in the amount of time. Further, since the control unit 8 changes the light emission amount by executing a program, parts such as a conventional variable resistor are not required, and the photoelectric switch can be downsized.

  In the second embodiment, the user can change the amount of emitted light at the use stage. However, the present invention is not limited to this, and the amount of emitted light corresponding to the current control value determined at the manufacturing stage is changed. You may make it the structure which cannot. Also in this configuration, since an appropriate current control value is set according to the variation characteristics of the light projecting elements for each photoelectric switch in the manufacturing stage, it is not excessive sensitivity and erroneous detection can be prevented.

  Further, the light projection current operation unit 20 as shown in the second embodiment may be applied to the photoelectric switch 1 according to the first embodiment. In the case of this configuration, as a means for the user to adjust the sensitivity, a change in threshold value and a change in light projection amount can be used. Also in the second embodiment, it goes without saying that the user can change the threshold value by applying the threshold value operation unit 15 as shown in the first embodiment.

  Further, the sensitivity adjustment is performed by changing the threshold value in the first embodiment and by changing the light projection amount in the second embodiment. However, the sensitivity adjustment is not limited to this. For example, the voltage amplification factor ( The sensitivity may be adjusted by adjusting (gain).

FIG. 6 is a block diagram showing a main part of the photoelectric switch 1 related to gain adjustment. The photoelectric switch 1 is newly provided with a gain operation unit 30 and a gain control unit 31, and is shown in FIGS. The threshold value operation unit 15, the threshold value setting unit 12, the light projection current operation unit 20, and the current control value setting unit 21 are not necessary. The other configuration is the same as that of the photoelectric switch 1 shown in FIG. 1 or FIG.
The gain control unit 31 outputs to the signal processing unit 7 a gain control value that controls a gain (amplification factor) when the optical signal (current) is converted into a voltage amplitude. The signal processing unit 7 amplifies the voltage amplitude with a gain corresponding to the gain control value.
The gain operation unit 30 includes a switch that receives an operation by the user, and outputs a gain amplification instruction to the gain control unit 31.
Thereby, in the use stage, the user can adjust the sensitivity by changing the gain.

  Note that there is an individual difference in the conversion efficiency at which the signal processing unit 7 converts the optical signal (current) received by the light receiving element 6 into a voltage amplitude, so even if the light receiving element 6 receives the same amount of received light, the signal processing The received light signal level (voltage) output from the unit 7 is not always the same. Further, the characteristics of the light projecting element 3 and the light receiving element 6 also vary. Therefore, at the manufacturing stage, the gain control unit 31 of the control unit 8 outputs so as to reduce the variation of the factor including any or all of the signal processing unit 7, the light projecting element 3, and the light receiving element 6 for each product. A gain control value may be set.

  For example, in the manufacturing stage, a predetermined reference signal is given to the light projecting drive unit 2 and received by the light receiving element 6 to measure the light reception signal level of the signal processing unit 7. Then, the gain setting unit 33 obtains the degree of variation in the actual light reception signal level of the signal processing unit 7 from the reference light reception signal level corresponding to the reference light amount, and corrects the gain control value according to the degree of variation. Then, a gain control value whose variation has been corrected is set in the gain holding unit 32. In the detection mode, the signal processing unit 7 amplifies the optical signal with a gain corresponding to the gain control value input from the gain control unit 31. Thereby, the dispersion | variation for every product can be reduced.

  Further, if the sensitivity is excessive, the photoelectric switch 1 may malfunction. Therefore, a gain corresponding to an appropriate sensitivity upper limit value that does not cause malfunction is determined and set in the gain control unit 31 as a gain upper limit value. Alternatively, the gain control value may be used as the upper limit value.

  Next, a case where the user performs sensitivity adjustment by operating the gain operation unit 30 to increase or decrease the gain of the signal processing unit 7 will be described. As with the threshold value operation unit 15 and the projection current operation unit 20 in the first and second embodiments, for example, every time the switch for increasing the gain (that is, increasing the sensitivity) of the gain operation unit 30 is pressed once, the gain A high level output signal is output from the operation unit 30 to the gain control unit 31, and conversely, every time the switch for lowering the gain (that is, lowering the sensitivity) is pressed once, the gain operation unit 30 returns to the gain control unit 31. A level output signal is output. In this case, the gain control unit 31 increases or decreases the gain control value set in the gain control unit 31 in accordance with the number of high level or low level output signals of the gain operation unit 30. At this time, the gain control unit 31 increases or decreases the gain control value in a range that is equal to or less than a preset upper limit value of the gain, but does not increase the gain control value any more if the upper limit value is exceeded.

  Thereby, it is possible to prevent the gain from being changed to an excessively high gain, and thus it is possible to prevent erroneous detection due to an excessive increase in sensitivity. Further, since the gain is adjusted using a microcomputer constituting the control unit 8, a conventional variable resistor is unnecessary.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to the configuration of the above-described embodiment, and the design does not depart from the gist of the present invention. Needless to say, the present invention is included in the present invention.
In the embodiment including FIG. 2, the description has been made on the assumption of a reflector type, particularly a photoelectric switch using a polarized reflector. However, the present invention is not limited to this. Is available.

DESCRIPTION OF SYMBOLS 1 Photoelectric switch 2 Light projecting drive part 3 Light projecting element 4 Light projecting lens 5 Light receiving lens 6 Light receiving element 7 Signal processing part 8 Control part 9 Light projecting control part 10 Comparison part 11 Threshold holding part 12 Threshold setting part 13 Output part 14 Mode Switching operation unit 15 Threshold operation unit 20 Light projection current operation unit 21 Current control value setting unit 22 Current control value holding unit 30 Gain operation unit 31 Gain control unit

Claims (8)

A light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region;
A light receiving unit that receives light from the light projecting unit and outputs a light reception signal at a level corresponding to the amount of light received;
A comparison unit for comparing the light reception signal output by the light receiving unit with a predetermined threshold value and determining the presence or absence of an object in the detection region;
A threshold value operating unit for receiving an instruction to increase or decrease the threshold value from the outside;
A lower limit value of a threshold value set based on a received light signal level output from the light receiving unit in a manufacturing process, and a new threshold value is set by increasing or decreasing the threshold value in response to an instruction from the threshold value operation unit A photoelectric switch comprising: a threshold value setting unit that sets a new threshold value according to an instruction when the threshold value is equal to or greater than the lower limit value, and sets the lower limit value as a new threshold value when the threshold value is smaller than the lower limit value. A light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region;
A light receiving unit that receives light from the light projecting unit and outputs a light reception signal at a level corresponding to the amount of light received;
A light projection current operation unit that receives an instruction to increase or decrease the light projection current of the light projection unit from outside,
In response to an instruction from the light projection current operation unit, a light projection control unit that changes a light projection current to be supplied to the light projection unit,
A comparison unit that compares the light reception signal output by the light receiving unit with a predetermined threshold and determines the presence or absence of an object in the detection region;
The photoelectric switch according to claim 1, wherein the threshold value is set based on a light receiving signal level output from the light receiving unit in a manufacturing process. A light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region;
A light receiving unit that receives light from the light projecting unit and outputs a light reception signal at a level corresponding to the amount of light received;
A comparison unit for comparing the light reception signal output by the light receiving unit with a predetermined threshold value and determining the presence or absence of an object in the detection region;
A light projection current operating unit for receiving an instruction to increase or decrease the light projection current from outside;
A light projecting current having an upper limit value of a light projecting current set based on a light receiving signal level output from the light receiving unit in a manufacturing process and supplied to the light projecting unit upon receiving an instruction from the light projecting current operating unit When the light projection current is less than or equal to the upper limit value, a new light projection current is set according to an instruction, and when the light projection current becomes larger than the upper limit value, the upper limit value is changed to the new light projection current. A photoelectric switch comprising a light projection control unit to be set. A light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region;
A light receiving unit that receives light from the light projecting unit and outputs a light reception signal at a level corresponding to the amount of light received;
A comparison unit for comparing the light reception signal output by the light receiving unit with a predetermined threshold value and determining the presence or absence of an object in the detection region;
A threshold value operating unit for receiving an instruction to increase or decrease the threshold value used for determination by the comparison unit from outside;
A threshold setting unit that receives an instruction from the threshold operation unit and changes a threshold used in the comparison unit;
The photoelectric switch of the light projecting unit is set based on a light receiving signal level output from the light receiving unit in a manufacturing process. A light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region;
A light receiving unit that receives light from the light projecting unit and outputs a light reception signal at a level corresponding to the amount of light received;
A gain operating unit for receiving an instruction to increase or decrease a gain when the light receiving unit converts the amount of received light into a light reception signal;
In response to an instruction from the gain operation unit, a gain control unit that changes the gain of the light receiving unit;
A comparison unit that compares the light reception signal output by the light receiving unit with a predetermined threshold and determines the presence or absence of an object in the detection region;
The photoelectric switch according to claim 1, wherein the threshold value is set based on a light receiving signal level output from the light receiving unit in a manufacturing process. A light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region;
A light receiving unit that receives light from the light projecting unit and outputs a light reception signal at a level corresponding to the amount of light received;
A gain operating unit for receiving an instruction to increase or decrease a gain when the light receiving unit converts the amount of received light into a light reception signal;
In response to an instruction from the gain operation unit, a gain control unit that changes the gain of the light receiving unit;
A comparison unit that compares the light reception signal output by the light receiving unit with a predetermined threshold and determines the presence or absence of an object in the detection region;
The photoelectric switch of the light projecting unit is set based on a light receiving signal level output from the light receiving unit in a manufacturing process. A light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region;
A light receiving unit that receives light from the light projecting unit and outputs a light reception signal at a level corresponding to the amount of light received;
A comparison unit for comparing the light reception signal output by the light receiving unit with a predetermined threshold value and determining the presence or absence of an object in the detection region;
A threshold value operating unit for receiving an instruction to increase or decrease the threshold value from the outside;
A photoelectric switch sensitivity adjustment method comprising a threshold setting unit configured to increase or decrease the threshold and set a new threshold in response to an instruction from the threshold operation unit,
The threshold value setting unit has a lower limit value of a threshold value set based on the received light signal level output from the light receiving unit in the manufacturing process, and the threshold value increased or decreased according to an instruction received from the threshold value operation unit is the lower limit value. In the above case, the threshold value is set as a new threshold value, and when the threshold value increased or decreased according to the instruction received from the threshold value operation unit is smaller than the lower limit value, the lower limit value is set as a new threshold value. How to adjust sensitivity. A light projecting unit that projects light of a light amount corresponding to the light projecting current to the detection region;
A light receiving unit that receives light from the light projecting unit and outputs a light reception signal at a level corresponding to the amount of light received;
A comparison unit for comparing the light reception signal output by the light receiving unit with a predetermined threshold value and determining the presence or absence of an object in the detection region;
A light projection current operating unit for receiving an instruction to increase or decrease the light projection current from outside;
A method for adjusting the sensitivity of a photoelectric switch, comprising: a projection current control unit configured to increase or decrease a projection current supplied to the projection unit in response to an instruction from the projection current operation unit and set a new projection current. There,
The light projection current control unit has an upper limit value of the light projection current set based on the light reception signal level output from the light reception unit in the manufacturing process, and increases or decreases according to an instruction received from the light projection current operation unit If the projected light current is less than or equal to the upper limit value, the projected current is set to a new projected current, and the projected current increased or decreased according to the instruction received from the projected current operation unit is greater than the upper limit value. In this case, the sensitivity adjustment method is characterized in that the upper limit value is set to a new light projection current.

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