JP2007142627A - Photoelectric sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid saturation of a display generated at the display section of limited number of digits in a photoelectric sensor equipped with a display function. <P>SOLUTION: Assuming a quantity of received light for "work is present" is "3000" and a quantity of light for "work is absent" is "21000", the threshold becomes (3000+21000)/2="12000". Since that value is larger than an upper limit display value "8000", display value of the threshold is adjusted to "8000" and the scaling factor is set to (8000/12000)="2/3" and then the display value of the quantity of received light is calculated, based on that scaling factor. The display value of the quantity of received light becomes "2000" for "work is present" and becomes "14000" for "work is absent". The display value "14000" of the quantity of received light for "work is absent" is displayed by the maximum value "9999" of 4 digits. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photoelectric sensor having a display function.

  For example, the photoelectric sensor shown in Patent Document 1 is roughly classified into a reflection type and a transmission type. The basic function of the photoelectric sensor is the amount of light received when a workpiece passes through a detection area formed by projected light. It is to determine the presence or absence of the work using the change of the. This type of photoelectric sensor generally includes a 4-digit display unit, and the received light amount and threshold value are displayed on the display unit.

  In other words, as disclosed in Patent Document 1, the photoelectric sensor amplifies the received light signal and then displays the data converted by the A / D converter as the received light amount.

In addition, the data (received light amount) digitally converted by the A / D converter uses the maximum received light amount and the minimum received light amount and typically automatically sets a threshold value in the middle. Is done.
Japanese Patent Laid-Open No. 09-167953

  The amount of light received and the threshold value exceeding the value that cannot be displayed on the 4-digit display section, that is, the value of “9999”, are virtually undisplayable. For example, when the received light data in the photoelectric sensor is “20000”, the display unit displays a value saturated with “9999”. Similarly, if the threshold value is set to “10200” when the maximum received light data is “20000” and the minimum received light data is “400”, the display of the threshold value is the display range of the 4-digit display section. There is a so-called saturation problem that the true value of the set value is not known.

  This means that even though the photoelectric sensor normally outputs an ON / OFF signal, the display value of the received light amount displayed on the display unit is easily saturated. Not only does this lead to unreliability, but the difference value between the amount of received light and the threshold value becomes substantially unknown, so it becomes impossible to fine-tune the threshold value, for example. There is.

  Accordingly, an object of the present invention is to provide a photoelectric sensor capable of avoiding display saturation that occurs in a display unit having a finite number of digits, on the premise of a photoelectric sensor having a display function.

The above technical problem is, according to the first aspect of the present invention,
The received light amount is compared with a threshold value based on the received light data that changes as the work passes through the detection area formed by the light projected by the light projecting unit, and the presence or absence of the work is determined. In a photoelectric sensor having a function of displaying a threshold value on a display unit,
The photoelectric sensor calculates the received light amount based on a value obtained by adding a plurality of the received light data, and has an operation mode in which the maximum value of the received light amount is larger than the display limit of the display unit,
This is achieved by providing a photoelectric sensor comprising display value adjusting means for adjusting display values of the received light amount and the threshold value to values that can be displayed on the display unit.

The above technical problem is, according to the second aspect of the present invention,
The received light amount is compared with a threshold value based on the received light data that changes as the work passes through the detection area formed by the light projected by the light projecting unit, and the presence or absence of the work is determined. In a photoelectric sensor having a function of displaying a threshold value on a display unit,
The photoelectric sensor calculates the received light amount based on a value obtained by adding a plurality of the received light data, and has an operation mode in which the maximum value of the received light amount is larger than the display limit of the display unit,
When the threshold value exceeds a predetermined upper limit value, the threshold value is adjusted to a predetermined display value that can be displayed on the display unit, and the threshold value is adjusted to the predetermined display value. This is achieved by providing a photoelectric sensor characterized in that the received light amount is adjusted based on the magnification at the time and displayed on the display unit.

  According to the present invention, display saturation can be avoided by adjusting the display value of the threshold value and the amount of received light.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a photoelectric sensor to which the present invention is applied. The illustrated photoelectric sensor 100 is a photoelectric sensor that projects and receives light through an optical fiber. The photoelectric sensor 100 has a narrow and narrow box-shaped casing 11, and optical fibers 14 and 15 extend from one end surface of the casing 11 to the outside. The output to the PLC (not shown) is performed through a cable 16 extending from the other end surface of the casing 11.

  First and second display portions 17 and 18 are provided on the elongated rectangular upper surface 11a of the casing 11 so as to be arranged side by side in the longitudinal direction. Both the first and second display portions 17 and 18 have four sections (four digits) arranged side by side, and each section is composed of a 7-segment LED.

  On the upper surface 11a of the casing 11, an output switching button 19, a mode switching switch (M key) 20, a swing type up / down adjustment switch 21, a sliding type operation mode selector switch 22, a set key switch (SET key) 23, An operation indicator lamp 24 is provided.

  The mode changeover switch (M key) 20 can switch the display mode of the screens of the first and second display units 17 and 18 by holding down this for 3 seconds or longer (long press). And a display mode (operation mode) during detection operation and a display mode (setting mode) for performing various settings. When the M key 20 is pressed for a time shorter than 3 seconds (short press), the screens of the first and second display units 17 and 18 can be switched without switching the display mode.

  The swing type up / down adjustment switch 21 can be adjusted, for example, to increase the threshold when the up (△) side is pressed, and can be adjusted to decrease the threshold when the down (▽) side is pressed. Can do. The up / down adjustment switch 21 is used for parameter selection and setting value adjustment in the setting mode.

  The slide-type operation mode selector switch 22 has two contacts. By operating this operation mode selector switch 22, an operation arbitrarily selected by the user from a preset operation mode and a plurality of other operation modes. Switching between modes can be performed. Examples of a plurality of operation modes that can be selected by the photoelectric sensor 100 are as follows. Various operation modes differ in the amount of received light. For example, (i ) Instead of setting a longer light reception period to reduce the pulse emission duty, the light emission current is increased to increase the light emission amount. (Ii) The light reception amount is increased by adding the received signal multiple times. At the same time, it is possible to adopt a technique for improving S / N.

(1) Fine mode: In this fine mode, for example, the amount of received light is set so as to be suitable for detecting the presence / absence of bearing markings, and it is possible to accurately discriminate slight changes in light intensity due to the presence / absence of minute markings. It has the feature of being able to.

(2) Turbo mode: The setting is such that the amount of received light is substantially increased compared to the fine mode, and is suitable for detecting, for example, a sticker on a mount.

(3) Super turbo mode: The setting is such that the amount of received light increases substantially more than in the turbo mode. This super turbo mode is used to detect the presence or absence of a workpiece W, for example, in a state where the workpiece W is separated from a light emitting element or a fiber that guides light from the light emitting element and / or a light receiving element or a fiber that guides light to the light receiving element. Is suitable.

(4) Ultra-turbo mode: The setting is such that the amount of received light is substantially increased compared to the super-turbo mode, and the light-receiving sensitivity is the highest among the operation modes listed here. This ultra turbo mode is suitable, for example, for detecting the presence or absence of a workpiece W farther away than the super turbo mode, or for detecting the workpiece W in a bad environment with a lot of dust and dirt.

(5) High-speed mode: The high-speed mode is set to increase the response speed compared to the various operation modes described above, and is suitable for detecting a workpiece W passing relatively quickly.

  The SET key 23 is used for automatic tuning and / or automatic threshold value setting which will be described later. The basic threshold value is set by pressing the SET key 23 with the work W (see FIG. 3) placed in the detection area, and then pressing the SET key 23 again with the work W removed from the detection area. When pressed, a value (typically an intermediate value) between the maximum amount of light received when the workpiece W is present and the minimum amount of light received when the workpiece W is removed is automatically set as a threshold value. The

  FIG. 2 is a block diagram of the photoelectric sensor 100. The photoelectric sensor 100 includes a light projecting processing unit 30 and a light projecting unit 31 for causing a light emitting element such as a light emitting diode (LED) to emit light, and a light receiving unit connected to a light receiving element composed of a photodiode or the like. 32 and an amplification unit 33, and an A / D conversion unit 34 that digitally converts the light reception signal amplified by the amplification unit 33 and outputs it as light reception data.

  The main control unit 35 that controls the light projecting unit 31 and the light receiving unit 32 basically includes a display calculation unit 36 and is configured by, for example, a gate array or a CPU. The main control unit 35 is supplied with signals from the operation unit 37 including the above-described various operation switches or buttons 19 to 23, and set values required for processing of the main control unit 35, such as those described above. The threshold value is set by the setting unit 38, the data processed by the main control unit 35 is supplied to the display calculation unit 36, and the data processed by the display calculation unit 36 is supplied to the first and second display units 17 and 18. Is supplied and displayed on the first and second display units 17 and 18.

  The photoelectric sensor 100 has a scaling function that increases or decreases the apparent value (display value) of the amount of received light by multiplying the received light signal converted by the A / D converter 34 with a scaling factor. The received light amount and the apparent threshold value can be displayed on the first and second display units 17 and 18.

  In addition, the photoelectric sensor 100 adjusts the scaling factor when the threshold value and / or the amount of received light displayed on the first and second display units 17 and 18 exceed a predetermined value by the automatic tuning function. Thus, the adjusted threshold value and received light amount can be displayed on the first and second display units 17 and 18.

  Before explaining the automatic tuning function, as shown in FIG. 3, the transmissive photoelectric sensor 100 has a work area W between the light projector 31 and the light receiver 32, that is, a detection area formed by light projected by the light projector 31. Then, in the transmissive type, the amount of received light decreases to X1 due to light shielding, and when the workpiece W passes the detection area, the amount of received light increases to X2.

The threshold value Th is obtained by the following equation.
Th = (X1 + X2) / 2

First embodiment (FIGS. 4 and 5)

  When the Th value of Th = (X1 + X2) / 2 is equal to or less than the threshold upper limit display value S, the threshold Th and the received light amounts X1, X2 are displayed, and the transmission type photoelectric sensor 100 has When the received light amount X2 of “no workpiece” exceeds the 4-digit display range, “9999” is displayed.

  When the threshold Th calculated based on the minimum and maximum values of the received light quantity acquired when the SET key 23 is tuned is larger than the upper limit display value S (Th> S), the automatic tuning mechanism operates. Then, with respect to the display of the first and second display portions 17 and 18, the threshold value is adjusted so as to become a predetermined display value (for example, the upper limit display value S) set in advance. After the display value is adjusted, it is displayed on the first and second display units 17 and 18. In the adjustment of the display value of the received light amount performed by this automatic tuning, “S / Th” is automatically set as the scaling magnification, and the display value of the received light amount is adjusted based on the scaling magnification. If the display value of the amount of received light is Y, this Y can be expressed by the following equation.

    Y = X · (S / Th)

  Note that it is preferable that the user can arbitrarily set the threshold upper limit display value S and the predetermined display value of the threshold.

  Specifically, referring to FIGS. 4 and 5, it is assumed that the received light amount X1 of “with workpiece” is “3000” and the received light amount X2 of “without workpiece” is “21000”. The threshold value Th is (3000 + 21000) / 2 = “12000” (step S10 in FIG. 5). If the upper limit display value S of the threshold value is “8000”, it is determined YES in step S11 of FIG. 5 by comparing the threshold value Th with the upper limit display value S, and the process proceeds to step S12. The display value of the value is adjusted to a predetermined display value (in this example, the upper limit display value “8000”), and a scaling magnification that matches this is calculated. That is, the scaling magnification is (8000/12000) = “2/3”, and the received light amount display value Y is obtained based on the scaling magnification. In this example, for example, when “work is present”, the display value of the received light amount is “2000”, and when “no work” is present, “14000”.

  The threshold value “8000” after automatic tuning and the display value “2000” for “with workpiece” are values that can be displayed in four digits, but the received value for “without workpiece” is “14000”. Since 4-digit display is impossible, the display values of the received light amount exceeding the maximum value “9999” of 4-digit display are all displayed as “9999”. After the display tuning is completed, the photoelectric sensor 100 displays the adjusted threshold value and the received light amount display value on the first and second display units 17 and 18.

Second embodiment (FIG. 6)

  Even in the second embodiment, a threshold value is calculated from the maximum and minimum received light amounts acquired at the time of tuning, and this threshold value is a threshold upper limit display value S such as “12000” as shown in FIG. Automatic tuning is performed when exceeding. In the automatic tuning in the second embodiment, the threshold value and the display value of the received light amount are adjusted based on the maximum received light amount acquired at the time of tuning. In the example of FIG. 6, since the maximum received light amount at the time of tuning is “21000”, the scaling factor for calculating the maximum value “9999” in the 4-digit display is calculated. That is, (9999/21000) = about 0.48 is automatically set as the scaling magnification, and the threshold value and the received light amount display value are adjusted based on the scaling magnification. Specifically, the display value of the threshold is adjusted to “5714”. For example, if the received light amount of “with workpiece” is “3000”, “1428” after adjustment is displayed as the adjusted value of the received light amount. .

Third embodiment (FIG. 7)

  Even in the third embodiment, the threshold is calculated from the maximum and minimum received light amounts acquired during tuning, and automatic tuning is performed when the threshold exceeds the upper limit display value S. In the third embodiment, the threshold value and the display value of the received light amount are adjusted based on the difference between the maximum received light amount and the minimum received light amount acquired during tuning.

  In the example of FIG. 7, the maximum received light amount at the time of tuning is “21000” and the minimum received light amount is “3000”. Therefore, the scaling value is set so that the difference value (21000−3000) = 18000 is the display width. Is calculated. Since the display width in 4-digit display is (9999-0) = "9999", (9999/18000) = approximately 0.56 is automatically set as the scaling factor, and the threshold value and light reception are based on this scaling factor. The display value of the quantity is adjusted. Specifically, the threshold value of “12000” is displayed as (12000−3000) × approximately 0.56 = “5000”. For example, the received light amount “3000” of “with workpiece” is (3000−3000) × approximately 0.56 = “0” is displayed.

Fourth embodiment (FIG. 8)

  In the fourth embodiment, a value that is, for example, 10% smaller than the maximum received light amount acquired at the time of tuning is set as a threshold value, and when this threshold value exceeds the upper limit display value S, the display value is automatically tuned. Done. In the fourth embodiment, the scaling factor is calculated so that the display value of the threshold value is a predetermined value, for example, “8000” which is the upper limit display value in the example of FIG.

  That is, in the illustrated example, the maximum received light amount is “21000”, and “18900”, which is 10% smaller than this, is the threshold value, but this “18900” is larger than the threshold upper limit display value “8000”. Is automatically tuned, (8000/18900) = approximately 0.42 is automatically set as the scaling factor used for this automatic tuning, the threshold value is "8000", and the received light amount is multiplied by approximately 0.42. The received value is the received light amount display value.

  Regarding the automatic setting of the threshold value, it is preferable that the user can arbitrarily set the percentage of what value is set smaller than the maximum received light amount.

  As described above, according to the embodiment of the present invention, when the threshold value or the amount of received light exceeds the display limit of the display unit, it can be displayed in a state of being automatically adjusted to be within the display range of the display unit. .

  Although the above embodiment has been described with an example in which the display value is automatically tuned by adjusting the scaling factor for the threshold value and the amount of received light, the received light gain and the amount of emitted light are changed instead of the adjustment of the scaling factor. The display value of the received light amount may be adjusted by the above.

It is a perspective view of a photoelectric sensor to which the present invention is applied. It is a block diagram of the photoelectric sensor of FIG. It is a figure for demonstrating the change of the light reception amount accompanying a workpiece | work passing the detection area which a transmissive photoelectric sensor forms. It is a figure for demonstrating the 1st Example of the automatic tuning of a display value. It is a flowchart for demonstrating an example of the control regarding the automatic tuning of a display value. It is a figure for demonstrating the 2nd Example of the automatic tuning of a display value. It is a figure for demonstrating the 3rd Example of the automatic tuning of a display value. It is a figure for demonstrating the 3rd Example of the automatic tuning of a display value.

Explanation of symbols

100 Photoelectric sensor 17, 18 First and second display parts 21 Swing type vertical adjustment switch 23 Set key switch (SET key)
33 Photoreceiver / Amplifier 34 A / D Converter W Work

Claims (8)

The received light amount is compared with a threshold value based on the received light data that changes as the work passes through the detection area formed by the light projected by the light projecting unit, and the presence or absence of the work is determined. In a photoelectric sensor having a function of displaying a threshold value on a display unit,
The photoelectric sensor calculates the received light amount based on a value obtained by adding a plurality of the received light data, and has an operation mode in which the maximum value of the received light amount is larger than the display limit of the display unit,
A photoelectric sensor comprising display value adjustment means for adjusting the display value of the received light amount and the threshold value to a value that can be displayed on the display unit.   2. The photoelectric sensor according to claim 1, further comprising an automatic threshold setting unit configured to set the threshold to a value between the maximum received light amount and the minimum received light amount.   A width between the maximum received light amount and the minimum received light amount is obtained, a magnification capable of adjusting the width to the maximum width of a numerical value that can be displayed on the display unit is obtained, and the threshold value is determined based on the magnification. The photoelectric sensor according to claim 2, wherein the photoelectric sensor adjusts the amount of received light.   3. The photoelectric device according to claim 2, wherein a magnification capable of adjusting the maximum received light amount to a maximum value that can be displayed on the display unit is obtained, the threshold value is adjusted based on the magnification, and the received light amount is adjusted. Sensor.   The photoelectric sensor according to claim 2, wherein when the threshold value exceeds a predetermined upper limit value, the received light amount and the display value of the threshold value are adjusted. The received light amount is compared with a threshold value based on the received light data that changes as the work passes through the detection area formed by the light projected by the light projecting unit, and the presence or absence of the work is determined. In a photoelectric sensor having a function of displaying a threshold value on a display unit,
The photoelectric sensor calculates the received light amount based on a value obtained by adding a plurality of the received light data, and has an operation mode in which the maximum value of the received light amount is larger than the display limit of the display unit,
When the threshold value exceeds a predetermined upper limit value, the threshold value is adjusted to a predetermined display value that can be displayed on the display unit, and the threshold value is adjusted to the predetermined display value. A photoelectric sensor, wherein the received light amount is adjusted based on a magnification at the time and displayed on the display unit.   The photoelectric sensor according to claim 6, further comprising threshold automatic setting means for setting the threshold to a value between the maximum received light amount and the minimum received light amount.   The photoelectric sensor according to claim 6, further comprising threshold automatic setting means for setting the threshold to a value that is reduced or increased at a predetermined rate from the average amount of received light.

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