JPS622486B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric switch suitable for detecting objects having a wide temperature range from low to high temperatures, such as steel products manufactured in a steel plant.

For example, in a steel plant, starting with high-temperature pig iron in a molten state obtained from a blast furnace, rolling and other steps are repeated in stages to finally produce various steel materials in a low-temperature state.

By the way, in the lines for manufacturing the various steel materials mentioned above, the presence or absence of the steel materials is detected and automatically controlled. However, as mentioned above, the temperature of steel materials in various lines ranges over a wide range from high to low temperatures, and the atmosphere is humid and dusty, making it necessary to detect steel materials under extremely poor conditions.

The prior art requires the use of multiple types of detectors that are not adversely affected by the temperature of each steel material. For example, a method of detecting steel by arranging a projector and a receiver between them has been used, but
Two devices were always required. Alternatively, a method of detecting steel materials in a predetermined temperature range by detecting radiant light has also been used, but detection of steel materials in a low temperature state is unstable or impossible.

The present invention has been made in view of the above circumstances, and its purpose is to
To provide a photoelectric switch capable of reliably detecting an object to be detected at a relatively high temperature with a single device.

An embodiment of the present invention will be described below with reference to the drawings.

First, the overall schematic configuration will be described with reference to FIGS. 1 to 3. Reference numeral 1 denotes a housing, which is composed of a case 2 and a cover 3. The case 2 is formed into a closed, substantially rectangular shape by a peripheral wall 4, a front wall 5, and a rear wall 6, and the rear wall 6 has a flange 7 projecting outward. Further, a substantially rectangular window 8 is formed in the front wall 5 of the case 1, and a transparent plate 9 forming a part of the window 8 is airtightly fitted into the window 8. Further, a bulging wall 10 is formed on the front wall 5 of the case 2 so as to bulge inward from the periphery of the window portion 8, and inside the bulging wall 10, a light projection chamber 12 is formed by a central partition wall 11. and light receiving chamber 13
It is divided into The cover 3 is formed into a substantially rectangular box shape with an open rear end surface by a peripheral wall 14 and a front wall 15, and the front wall 15 has a substantially rectangular opening 1.
6 is formed, and a guide protrusion 17 is provided on the inner surface of the peripheral wall 14 in a substantially spiral shape. The cover 3 is fitted onto the case 2 so as to cover the peripheral wall 4 thereof, and its rear end opening is attached to the flange 7 by screws or the like. As a result, a flow path 18 is formed between the circumferential wall 4 of the case 2 and the circumferential wall 14 of the cover 3, and furthermore, a flow path 18 is formed between the front wall 4 of the case 2 and the front wall 14 of the cover 3. A slit-shaped discharge hole 19 is formed at the upper side and communicates with the flow passage 18 . The flow path 18 is formed by the guide protrusion 17 so as to have a substantially spiral shape. Reference numeral 20 denotes an air supply port body attached to the rear wall 6 of the case 2, which communicates with the rear part of the flow path 18 and connects the flow path 1
8. Air supply source such as compressor (not shown)
The system is designed to supply cooling air from the
On the other hand, 21 is a light emitting element made of a light emitting diode or the like that emits infrared rays, and this is connected to the bulging wall 1.
The light projection lens 22 is arranged on the back wall on the side of the light projection chamber 12 in 0 and is attached to the front end of the light projection chamber 12.
It has become compatible with Reference numeral 23 denotes a first light-receiving element made of a silicon phototransistor or the like.
The translucent mirror 24 is disposed facing the light-receiving chamber 13 at an angle of 45 degrees, and corresponds from above in a direction perpendicular to the light-receiving axis. Reference numeral 25 denotes a light receiving lens attached to the front end of the light receiving chamber 13. 26 is a second light-receiving element made of a silicon phototransistor or the like, which is disposed on the back wall of the bulging wall 10 on the light-receiving chamber 13 side, and corresponds to the semi-transparent mirror 24 from the rear. ing. Incidentally, reference numerals 27 and 28 are filters for cutting off visible light, which are disposed in the upper and inner parts of the light receiving chamber 13, facing the light receiving elements 23 and 26, respectively. Further, 29 is an operation indicator light attached to the rear wall 6 of the case 2, and 30 and 31 are a power connector and a signal connector attached to the rear wall 6, respectively. Reference numeral 32 denotes a circuit board made of a printed circuit board disposed inside the case 2, and a circuit device 33 is configured on this circuit board.

Now, this circuit device 33 will be explained with reference to FIG. First, the reflected light detection system circuit 34 related to the light emitting element 21 and the first light receiving element 23 will be described. Reference numeral 35 denotes an oscillation circuit that generates a rectangular pulse-shaped oscillation output, and the oscillation output is given to the light emitting element 21 via the drive circuit 36, thereby causing the light emitting element 21 to e.g.
It is designed to generate pulse modulated infrared radiation of 940nm. Moreover, the first light receiving element 23 has a diameter of 300n.
The detected electric signal is supplied as one input signal to the synchronous detection circuit 38 via an AC amplifier (actually, it consists of a preamplifier and a main amplifier) 37. It's getting old. This synchronous detection circuit 38 receives the oscillation circuit 3 as the other input signal.
5 oscillation output is provided, and after synchronizing the detected electrical signal and the oscillation output, a pulse output signal of, for example, positive (+) polarity is generated. Further, the pulse output signal of this synchronous detection circuit 38 is given to an integrating circuit 39, and the integrated output signal of this integrating circuit 39 is given to a waveform shaping circuit 40 consisting of a Schmitt circuit, etc., and the waveform shaping circuit 40 When the signal exceeds a certain level, a high level (H) detection output signal is generated. Next, the radiation light detection system circuit 41 related to the second light receiving element 26 will be described. The second light-receiving element 26 has a light-receiving band of 300 nm to 1100 nm, and its detection electric signal is given as an input signal to one of the modulation circuits 42 of the accumulation effect light reception method, for example. A rectangular pulse-shaped oscillation output from the oscillation circuit 43 is provided as an input signal. In this case, the modulation circuit 42 of the storage effect light reception type has a well-known structure (if necessary, it can be used as described in the Optoelectronics Handbook, pages 83 and 84).
Pages, pages 86 and 87 ~ Ohmsha Co., Ltd. 1972
(Refer to issue published on March 31, 2016), so the general configuration will be explained below with reference to FIG. 6. That is, in principle, in the modulation circuit 42, the collector of the second light receiving element 26 made of a phototransistor is connected to the power supply terminal 42.
a, the emitter of the second light receiving element 26 is grounded via a resistor 42b, and an output terminal 42c is connected to a common connection point between the emitter of the second light receiving element 26 and the resistor 42b. 7a from the oscillation circuit 43 to the power supply terminal 42a.
When pulses with pulse width (mark width) Ta are applied at intervals of time (space width) Tb as shown in _{FIG .} has a peak value and h _FE C _B
A level output signal V ₀ having a time constant of cR _L is obtained. Here, I _L is the collector of the light receiving element 26.
The photocurrent obtained by functioning as a photodiode when the p-n junction between the emitters is reverse biased, _hFE is the current amplification factor of the light receiving element 26,
C _B c is the junction capacitance when a reverse bias is applied between the collector and base of the light receiving element 26, and R _L is the resistance 42
b is the resistance value. In the modulation circuit 42, when the temperature of the object to be detected is low and the level of radiated light to the light receiving element 26 is low, the decrease in charge of the light receiving element 26 is small, so the change in the peak value is small and no level output signal is generated. Thus, the level output signal of the modulation circuit 42 is provided as one input signal of the synchronous detection circuit 45 via the AC amplifier 44. Moreover, this synchronous detection circuit 4
5 receives the oscillation output of the oscillation circuit 43 as the other input signal, and generates, for example, a positive pulse output signal after synchronizing the level output signal and the oscillation output. Furthermore, the pulse output signal of this synchronous detection circuit 45 is given to an integrating circuit 46, and the integrated output signal of the integrating circuit 46 is given to a waveform shaping circuit 47 consisting of a Schmitt circuit, etc. Signal is above a certain level (above a certain amount of radiation from the object to be detected)
When this happens, a high level detection output signal is generated. On the other hand, the reflected light detection system circuit 3
The detection output signal of the waveform shaping circuit 40, which is the detection output signal of No. 4, and the detection output signal of the waveform shaping circuit 47, which is the detection output signal of the radiation light detection system circuit 41, are supplied to an OR circuit 48, and the OR circuit The output signal of 48 is applied to the operation indicator lamp 29 and also to the excitation coil 49A of the relay 49. And the operation indicator light 29
is energized and turned on when a high-level output signal is given from the OR circuit 48, and the relay 49 is activated when the excitation coil 49A is energized when a high-level output signal is given from the OR circuit 48, and the relay switch 49B is normally closed. The side contact b is opened and the normally open side contact a is closed. Note that the contact output of this relay switch 49B is taken out to the outside via the signal connector 31. Also, 5
0 is a DC power supply circuit that supplies constant voltage DC power to the circuit device 33, and AC power is applied to this through the power outlet 30.

Next, the operation of this embodiment having the above configuration will be explained with reference to FIG.

When DC constant voltage power is applied to the circuit device 33 from the DC power supply circuit 50, the oscillation output of the oscillation circuit 35 is first applied to the light emitting element 21 via the drive circuit 36, and the light emitting element 21 emits pulse modulated infrared rays A. The object to be detected 51 is irradiated through the lens 22 and the transparent plate 9. The pulse modulated infrared rays A irradiated onto the detected object 51 are reflected by the detected object 51 and become reflected pulse modulated infrared rays B, which enters the light receiving chamber 13 via the transparent plate 9 and the light receiving lens 25. 50% of the light is reflected by the semi-transparent mirror 24 and enters the first light receiving element 23 via the filter 27, and the remaining 50% passes through the semi-transparent mirror 24 and passes through the filter 28. second light receiving element 2
The light enters at 6. In addition, the radiant light C emitted from the object to be detected 51 enters the light receiving chamber 13 in the same manner, 50% of it enters the first light receiving element 23, and the remaining 50% enters the second light receiving element 23. The light enters the light receiving element 26 of. In this case, when the temperature of the detected object 51 is below 500°C, the radiation C emitted from the detected object 51
Since the level D of (900 nm or less) is lower than the saturation level J of the first light receiving element 23, as shown in FIG. Light enters the element 23. Therefore, the output signal G of the AC amplifier 37 that amplifies the alternating current signal that is the alternating current component of the pulse output signal F shown in FIG. 5a as the detected electric signal of the first light receiving element 23 is as shown in FIG. 5b. Based on this, the waveform shaping circuit 40 generates a high-level detection output signal I as shown in FIG. 5d. Moreover, the detected object 51
When the temperature is at a medium temperature of 500°C or higher, the level D of the radiated light C gradually approaches the saturation level J of the first light receiving element 23, and the peak level of the output signal G of the AC amplifier 37 becomes low. Become. and,
When the temperature of the detected object 51 is approximately 700°C, the first
The light receiving element 23 of has reached the saturation level J,
The output signal G of the AC amplifier 37 becomes smaller than the reflected light operation level E and is no longer output. Therefore,
The output signal of the waveform shaping circuit 40 is low level (L)
becomes. As described above, in the reflected light detection system circuit 34, when the temperature of the detected object 51 is approximately 700° C. or higher, the detection operation becomes unstable or impossible due to an increase in the level of the DC component based on the radiated light C. It is. On the other hand, when the temperature of the detected object 51 is low, such as 500° C. or less, the level D of the radiant light C is low as described above, so the amount of the radiant light C incident on the second light receiving element 26 is extremely low. If the current is low, the charge reduction of the second light receiving element 26 is small, and therefore the AC amplifier 44 does not generate an output signal. When the temperature of the object to be detected 51 is approximately 500° C., the radiation light C has a predetermined wavelength of approximately 900 nm, and its level D becomes high. Therefore, the amount of light incident on the second light receiving element 26 increases When the radiant light operation level N shown in FIG. Therefore, the AC amplifier 44 generates a level output signal K as shown in FIG. 5c. and,
Based on this level output signal K, the waveform shaping circuit 4
7 generates a high level detection output signal M as shown in FIG. 5e. As described above, in the radiation light detection system circuit 41, when the temperature of the detected object 51 is approximately 500° C. or less, the radiation light C is level D.
If the value is low, the detection operation becomes unstable or impossible. Thus, the waveform shaping circuits 40 and 4
Since the high-level detection output signals I and M of No. 7 are given to the OR circuit 48, the OR circuit 48 comes to generate a high-level output signal, and based on this, the operation indicator lamp 29 is turned on and activated. The relay 49 is activated and the relay switch 49B is switched to open the normally closed contact b and close the normally open contact a. According to experiments conducted by the present inventor, the reflected light detection system circuit 34 can perform a reliable detection operation even when the temperature of the detected object 51 is as low as about -10°C, and the radiated light detection system circuit 41 Accordingly, results have been obtained that a reliable detection operation can be performed even when the temperature of the detected object 51 is as high as about 1300°C.

Now, during the detection operation of the circuit device 33 as described above, cooling air is supplied from the air supply source to the flow path 18 via the air supply port body 20. Thus, the cooling air supplied to the flow path 18 flows through the guide protrusion 17.
The air is guided approximately spirally around the outer surface of the peripheral wall 4 of the case 2 and flows forward to cool the case 2. After that, the air is sent from the front end of the flow path 18 to the discharge hole 19 to cool the case 2. The discharge is now directed downward from the discharge hole 19, and moisture, dust, etc. present on the front side of the transparent plate 9 in the window 8 are blown away by the discharge flow, and The discharge flow acts as a kind of air curtain to prevent moisture, dust, etc. from adhering to the front surface of the transparent plate 9.

According to this embodiment, the reflected light detection system circuit 34 that irradiates the detected object 51 with pulse modulated infrared rays A and detects the reflected pulse modulated infrared rays B and the detected object 51 are housed in the same housing 1. A radiant light detection system circuit 41 is provided to detect the radiant light C emitted from the radiant light C, and the OR output of the respective detection output signals I and M is obtained.
A single device can reliably detect objects 51 having a wide range of temperatures up to temperatures as high as ℃.
Moreover, in the medium temperature range of about 500°C to about 700°C, which is near the lower limit detection temperature of the radiant light detection system circuit 41 and the upper limit detection temperature of the reflected light detection system circuit 34, the detection output signals I of both circuits 34, 41, Since M is set to occur at the same time, it is possible to reliably prevent the occurrence of parts that would cause unstable detection operation in the temperature range of the detected object. It is suitable for steel plants that need to detect steel materials, and is extremely convenient for automation as there is no need to use multiple types of detectors. Furthermore, according to this embodiment, since the light incident on the first light receiving element 23 and the second light receiving element 26 is divided into 50% by the semi-transparent mirror 24, the light incident on both is coaxial. Therefore, each of the light receiving elements 23 and 26 detects the reflected pulse modulated infrared rays B and the radiated light C from the same part of the detected object 51, and the detection position will not be deviated due to temperature fluctuations. .

Further, according to this embodiment, the housing 1 is composed of the case 2 and the cover 3, and the flow passage 18 is formed between the two, and the cooling air is made to flow through the flow passage 18. The case 2 can be effectively cooled, and the components of the circuit device 33 disposed within the case 2 can operate well without being affected by heat. It is effective in places with high temperature atmosphere. Moreover, according to this embodiment, the deteriorating air flowing through the flow path 18 is discharged to the front side of the transparent plate 9 of the window section 8 from the discharge hole section 19 formed between the front ends of the case 2 and the cover 3. As a result, moisture, dust, etc. existing on the front side of the transparent plate 9 are blown away by the air flow from the discharge hole 19, and do not adhere to the transparent plate 9. Therefore, the transparent plate 9 There is no problem that the transmission of infrared rays and radiant light is obstructed due to moisture, dust, etc. adhering to the plate 9, and it is suitable for use in a place with a high humidity atmosphere or a place with a dusty atmosphere.

The present invention is not limited to the embodiments described above and shown in the drawings, and may be modified as appropriate without departing from the scope of the invention, for example, the shape and structure of the housing 1 may be appropriately selected. Of course, it can be implemented.

As explained above, the present invention provides a light emitting element that radiates pulse modulated infrared rays toward a detected object in a housing, and includes a light emitting element that emits pulse modulated infrared rays reflected from the detected object and emitted from the detected object within the housing. A reflected light detection system circuit that includes first and second light receiving elements that receive emitted radiant light and detects when an electrical signal of the first light receiving element is an alternating current signal, and the second light receiving element. The structure is equipped with a radiation light detection system circuit that detects when the electric signal of the element is a level signal based on a predetermined wavelength or more and a predetermined amount of radiation light, so it can be used from temperatures as low as -10°C, for example.
A single device can reliably detect objects with a wide range of temperatures, up to temperatures as high as 1300°C, and operation becomes unstable, especially in the medium temperature range from about 500°C to about 700°C. It is possible to provide a photoelectric switch that can reliably prevent this.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is an exploded perspective view of the case and cover, FIG. 2 is a vertical side view, FIG. 3 is a sectional view taken along the line of FIG. Figure 4 is a block diagram of the circuit device, Figure 5a
7e are waveform diagrams of each part for explaining the operation, FIG. 6 is a diagram of the basic configuration of the modulation circuit, and FIGS. 7a and 7b are waveform diagrams of the same circuit. In the drawing, 1 is the housing, 2 is the case, 3 is the cover,
8 is a window portion, 18 is a flow path, 19 is a discharge hole portion, 21
23 is a light-emitting element, 23 is a first light-receiving element, 24 is a semi-transparent mirror, 26 is a second light-receiving element, 33 is a circuit device, 34 is a reflected light detection system circuit, 41 is a radiated light detection system circuit, and 51 is a target Indicates the object to be detected.

Claims (1)

[Scope of Claims] 1. A light-emitting element provided within a housing that emits pulse-modulated infrared rays toward a detected object, and a light-emitting element provided within the housing that receives and emits pulse-modulated infrared rays reflected from the detected object. a first light-receiving element that detects and converts it into an electrical signal; a reflected light detection system circuit that obtains a detection signal when the amplified light-receiving signal outputted from the first light-receiving element is equal to or higher than a predetermined value; a second light-receiving element that is installed in the detector and detects the radiant light emitted from the object to be detected; the detection signal of the second light-receiving element is modulated by accumulation effect, and the AC signal is amplified so that the radiant light has a predetermined wavelength; A photoelectric switch comprising: a radiation detection system circuit that detects radiation when the amount is above a predetermined amount; and an OR circuit for the outputs of the respective detection system circuits. 2. The housing consists of a case that has a window section on the front surface that allows pulse modulated infrared rays and radiant light to pass through, and a cover that covers the peripheral wall of the case and forms a flow path for circulating cooling air between the case and the peripheral wall. and a discharge hole is formed between the front end of the cover and the case to discharge the cooling air that has passed through the flow path to the front side of the window. A photoelectric switch according to scope 1. 3. A patent characterized by forming a structure in which pulse modulated infrared rays and radiation light can be received on the same axis and by the same light receiving element, and a structure in which two of the light receiving elements are arranged at an angle of 90 degrees. A photoelectric switch according to claim 1.