JPH0678929U - Optical limit switch - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an optical limit switch with less deterioration over time, reliable operation, and high reliability. [Structure] A pressure sensitive element 11 made of a photoelastic material, and an operation section 2
The external force applied to 9a is transmitted to the pressure-sensitive element 11 through the lever 28, and the pressure-sensitive element 11 is pressed with a pressure corresponding to the amount of displacement of the operating portion.
The pressure mechanism 12 for applying pressure to the pressure sensitive element 11 and the polarizer 18 on the pressure sensitive element 11.
A light input section for making light incident through the light output section, and a light output section for making light transmitted through the pressure sensitive element 11 go out through the analyzer 20;
A light receiving device is provided which discriminates the amount of light emitted from the light output portion and generates a detection output indicating that the operating portion is at a predetermined position.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical limit switch that uses light to perform a detection operation similar to a conventional limit switch.

[0002]

[Prior art]

 In various devices having a mechanically movable portion, a limit switch is used to detect whether or not the movable portion has reached a predetermined position. For example, in a switch such as a circuit breaker or a disconnector, in order to detect that the switch has completed the opening or closing operation, the ON operation is performed when the movable contact reaches the opening or closing position. Has a limit switch that turns off.

Conventionally, as a limit switch, a mechanical limit margin switch having a mechanical contact that is turned on and off according to a displacement of an operating portion has been widely used, but when a mechanical limit switch is used, When the electrical noise was generated in the vicinity of the limit switch, the noise could penetrate the detection device through the limit switch. In particular, when a mechanical limit switch is used to detect the operation of the switch in a device to which a high voltage is applied, such as a gas-insulated switchgear, the surge generated in the device is passed through the limit switch to the detection circuit. There was a risk that it could invade and damage the detector.

Therefore, when detecting the position of a movable body in an environment where electrical noise or surge occurs, use an optical limit switch that uses light to perform the same detection operation as a mechanical limit switch. Is being considered.

FIG. 8 shows a structure of an already proposed optical limit switch. In FIG. 8, 1 is a switch case, and 2 and 3 are optical fibers whose one ends are connected to a light source 4 and a light receiving device 5, respectively. The other ends of these optical fibers are arranged to face each other in the case 1.

Reference numeral 6 denotes a case 1 which is displaced between a light-shielding position where it blocks the opposing ends of the optical fibers 2 and 3 as shown by a chain line in the case and a retracted position shown by a solid line in the figure. A light-shielding plate supported so as to obtain the light-shielding plate, and the light-shielding plate is biased toward the retracted position by a return spring 7. A lever 8 is rotatably supported by the case 1, and a switch operation portion 9 is provided at a free end portion of the lever 8. The lever 8 comes into contact with the knob 6a attached to the light shielding plate 6 to displace the light shielding plate 6 between the retracted position and the light shielding position. When the light shielding plate 6 is in the retracted position, the light is incident on the optical fiber 3 from the optical fiber 2, so that the light receiving device 5 detects the light. When a movable body (not shown) comes into contact with the operating portion 9 and operates the operating portion 9 to move the light shielding plate 6 to the light shielding position, the light shielding plate 6 shields between the optical fibers 2 and 3, so that the light receiving device 5 Stops detecting light. Since the light receiving device 5 generates an output signal whose state differs depending on whether it is detecting light or not, it is possible to detect that the operation unit is operated from the output state of the light receiving device. it can.

When such an optical limit switch is used, since the mounting portion of the limit switch and the light receiving device are connected by an optical fiber, it is possible to prevent a surge from entering the light receiving device side.

[0008]

[Problems to be solved by the device]

 In the proposed optical limit switch shown in Fig. 8, there is a sliding part in the part that supports the shading plate, so the switch is operated when the sliding part is rusted or the sliding part is worn. As a result, the operating force required for this may change, and reliability was poor. In addition, since the optical limit switch shown in FIG. 8 has a mechanical sliding portion, the main part of the optical system that constitutes the switch (in the example of FIG. 8, the opposite ends of the optical fibers 2 and 3) is completely removed. It was difficult to shield from the outside. Therefore, there is a possibility that the operation of the switch may become uncertain due to the infiltration of moisture into the main part of the optical system to cause dew condensation or the attachment of dust.

The purpose of the present invention is to prevent the operation of the optical system from becoming uncertain due to water and dust adhering to the main part of the optical system, and to prevent the operating characteristics from changing due to deterioration over time, thereby improving reliability. It is to provide an optical limit switch with improved life and extended life.

[0010]

[Means for Solving the Problems]

 The optical limit switch according to the present invention transmits a pressure-sensitive element made of a photoelastic material and an external force applied to the operating section to the pressure-sensitive element via a lever to generate a pressure-sensitive pressure corresponding to the displacement of the operating section. A pressure mechanism that presses the element, a light input section that allows light to enter the pressure-sensitive element through a polarizer, a light output section that outputs the light that has passed through the pressure-sensitive element through an analyzer, and an output from the light output section. And a light-receiving device that discriminates the amount of light and generates a detection output indicating that the operation unit is at a predetermined position.

In the light receiving device, for example, a light receiving circuit that converts light emitted from the light output unit into an electric signal, and the electric signal is set to a first determination value and a value higher than the first determination value. A second comparison value and a comparison circuit for comparing, the first detection output is generated when the electric signal is lower than the first judgment value, and the electric signal is higher than the second judgment value. To generate a second detection output.

It is preferable that the pressure sensitive element and the light input portion and the light output portion are covered with a molding material and sealed.

[0013]

[Action]

 As described above, the force acting on the operating portion is transmitted to the pressure-sensitive element made of a photoelastic material through the lever so that the pressure-sensitive element is pressed with a pressure corresponding to the displacement amount of the operating portion, and the pressure sensitive element is detected. When the light transmitted through the pressure element is detected through the analyzer, the amount of light detected through the analyzer changes according to the amount of displacement of the operating portion. Therefore, by discriminating the amount of light detected through the analyzer with the light receiving device, it is possible to obtain a signal indicating that the mover is at a predetermined position, and to perform the same detection operation as a conventional limit switch. You can

As described above, if the force acting on the operation portion is transmitted to the pressure-sensitive element via the lever, it is not necessary to provide a mechanical sliding portion, so that deterioration over time can be reduced. Therefore, reliability can be improved.

[0015]

【Example】

 FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 11 is a pressure sensitive element made of a transparent photoelastic material having a photoelastic effect such as glass or plastics. The pressure-sensitive element is formed in, for example, a rectangular parallelepiped shape or a cubic shape, and two surfaces 11a and 11b facing each other serve as an entrance surface and an exit surface, respectively, and the other two opposite surfaces 11c and 11d are formed. It is a pressure surface. Reference numeral 12 is a pressurizing mechanism for transmitting an external force applied to the operating portion to the pressure sensitive element via a lever to pressurize the pressure sensitive element with a pressure P corresponding to the displacement amount of the operating portion, and 13 is a light source 14 to an optical fiber 15 And a collimator 16 to provide a linearly polarized light component of the light to the incident surface 11a of the pressure sensitive element 11. The illustrated optical input section 13 is composed of a polarizer 18 and one end of an optical fiber 17 connected to the polarizer 18, and the other end of the optical fiber 17 is connected to a collimator 16.

Reference numeral 19 denotes a light output section for passing the linearly polarized light component of the light transmitted through the pressure sensitive element 11. This light output section is connected to the analyzer 20 and one end of an optical fiber 21 connected to the analyzer. It is composed of. The other end of the optical fiber 21 is connected to the light receiving device 24 through a collimator 22 and an optical fiber 23.

FIG. 2 shows the pressure-sensitive element 11 and a pressure mechanism for pressing the pressure-sensitive element. In this example, a case 25 made of a transparent material such as plastic is provided and the case is provided. Holds a polarizer 18 and an analyzer 20 and ends of the optical fibers 17 and 21 in a molded state. The polarizer 18 and the analyzer 20 are respectively brought into contact with the entrance surface 11a and the exit surface 11b of the pressure sensitive element 11, and the ends of the optical fibers 17 and 21 are coupled to the polarizer 18 and the analyzer 20, respectively. ing.

Further, one end of the pressure block 26 is brought into contact with one pressure surface 11 c of the pressure sensitive element, and a protrusion 26 a provided at the other end of the pressure block 26 penetrates the case 25 and is guided to the outside. ing. One end of a lever 28 is supported on the case 25 by a pin 27, and an intermediate portion of the lever 28 is brought into contact with a tip of a protrusion 26 a of the pressure block 26. The other end of the lever 28 is connected to the rear end of a contact 29 made of a plate of elastic material bent in a V shape, and the tip of the contact 29 serves as an operating portion 29a of the optical limit switch. One end of a leaf spring 30 is fixed to one end of the lever 28, and the other end of the leaf spring 30 is in contact with the side surface of the case 25. The leaf spring 30 restricts the lever 28 from rotating clockwise in the drawing.

In the example shown in FIG. 2, the pressurizing mechanism 12 is constituted by the pressurizing block 26, the lever 28, and the contactor 29, and an external force in the direction of the arrow shown in the figure is applied to the operating portion 29a at the tip of the contactor 29. When f is applied, the contact 29 is deformed and the operating portion 29a is displaced, and at this time, the pressure P corresponding to the displacement amount of the operating portion 29a is applied to the pressure sensitive element 11. .

As described above, when the pressure P is applied to the photoelastic material arranged between the polarizer and the analyzer, the output light amount A obtained through the analyzer changes with the pressure P. The characteristics of the change in the output light amount A with respect to the pressure P differ depending on the arrangement of the polarizer 17 and the analyzer 19. That is, when the direction of the linearly polarized light of the polarizer 17 and the direction of the linearly polarized light of the analyzer 19 are arranged so as to be orthogonal to each other (cross arrangement), as shown in FIG. When the characteristic that the output light amount A increases is obtained, and the direction of the linearly polarized light of the polarizer 17 and the direction of the linearly polarized light of the analyzer 19 are arranged in parallel (parallel arrangement), FIG. As shown, the output light amount A decreases as the pressure P increases. Therefore, by discriminating the output light amount A by the light receiving device 22, it is possible to obtain a detection output for identifying the position of the operating portion. Note that it is preferable to use the mode shown in FIG. 6A in order to facilitate the discrimination of the light amount level.

As shown in FIG. 7C, when the force applied from the pressure block to the pressure sensitive element 11 is F 1 and the surface area (pressure receiving area) to which the force F is applied is S, the pressure sensitive element is When pressed, stress ρ = F / S is generated in the pressure sensitive element. When the polarizer and the analyzer are arranged in a cross arrangement, the relationship between the output light quantity and the force F when the stress is ρ1 and ρ2 is as shown by the curves a and b in FIG. 7 (A), respectively. . When the polarizer and the analyzer are arranged in parallel, the relationship between the output light quantity and the force F when the stress is ρ1 and ρ2 is as shown by the curves a and b in Fig. 7 (B), respectively. is there. From these characteristics, it is understood that the forces required to obtain the predetermined light amount Io when the stress is ρ1 and ρ2 are F2 and F1 (F2 <F1), respectively. That is, if the pressure receiving area is reduced and the stress generated in the pressure sensitive element is increased, a predetermined change in the amount of light can be obtained even if the force applied to the pressure sensitive element is reduced.

In the above embodiment, a high level detection output is generated when an external force is applied to the operating portion of the switch to displace the operating portion beyond the first limit position to the second limit position. And Further, it is assumed that the detection output is changed to the low level when the external force is reduced from the state where the high level detection output is generated and the operation unit is returned to the first limit position. Here, for example, the polarizer and the analyzer are arranged in a cross arrangement, and as shown in FIG. 6 (A), the judgment values AL and AH (AL <AH) of the output light amount are set, and the operation section is set to the first limit. The pressure applied to the pressure sensitive element is set to P1 and P2 respectively when the switch is in the position and the second limit position. In this case, when the operation unit is in front of the first limit position and the output light amount A is smaller than the determination value AL, a low level detection output is generated, and the operation unit reaches the second limit position to output light. By generating a high-level detection output when the quantity A reaches the judgment value AH, the same detection operation as that of the conventional limit switch can be performed. The light receiving device 24 includes a light receiving circuit 31 for converting the light emitted from the light output portion into an electric signal Vs, and a first judgment value VL for the electric signal Vs and a first judgment value VL set higher than the first judgment value VL. The first detection output is generated when the electric signal Vs is lower than the first judgment value VL as compared with the second judgment value VH, and the first detection output is generated when the electric signal Vs is higher than the second judgment value VH. 2 and a signal output circuit 32 for generating a detection output. The signal output circuit 32 shown in the figure outputs the comparison circuit CM1 for comparing the electric signal Vs with the first judgment value VL, the comparison circuit CM2 for comparing the electric signal Vs with the second judgment value VH, and the output of the comparison circuit CM1. And a flip-flop circuit F / F which is reset and set by the output of CM2. The comparator circuit CM1 produces a high level (hereinafter referred to as H level) output when the electric signal Vs is lower than the first judgment value VL, and outputs a low level when the electric signal Vs is higher than the first judgment value VL. Generates level (hereinafter L level) output. Further, the comparison circuit CM2 generates an L level output when the electric signal Vs is lower than the second judgment value VH, and an H level output when the electric signal Vs is higher than the second judgment value VH. To do.

When the electric signal Vs is lower than the first judgment level VL, the output of the comparison circuit CM1 is at the H level and the output of the comparison circuit CM2 is at the L level, so that the flip-flop circuit F / F is reset. , The positive logic output Q of the flip-flop circuit becomes L level. This L level output signal is the first detection output.

When the electric signal Vs exceeds the first judgment value VL and is less than the second judgment value VH, the output of the comparison circuit CM1 becomes L level, and the output of the comparison circuit CM2 is also L level. The state of the output Q of the flip-flop circuit F / F does not change. Next, when the electric signal Vs exceeds the second judgment value VH, the output of the comparison circuit CM1 holds the L level and the output of the comparison circuit CM2 becomes the H level, so that the flip-flop circuit F 1 / F 2 is set. Then, the positive logic output Q becomes H level. This H-level output is the second detection output. When the electric signal Vs becomes lower than the second judgment value VH from this state, the output of the comparison circuit CM1 holds the L level and the output of the comparison circuit CM2 becomes the L level, but the state of the flip-flop circuit F / F. Does not change and the state of the output of the flip-flop does not change. When the electric signal Vs further decreases and becomes lower than the first judgment value VL, the output of the comparison circuit CM1 becomes H level, the flip-flop circuit F / F is reset, and its output Q becomes L level.

Therefore, in this embodiment, the first detection output is generated when the electric signal Vs is lower than the first judgment level VL, and the second detection output is generated when the electric signal exceeds the second judgment level VH. To occur. Next, when the electric signal Vs drops from this state and becomes lower than the first determination level VL, a second detection output is generated. The region between the first determination level VL and the second determination level VH is a dead zone, and the detection output does not change when the electric signal is in this dead zone.

FIG. 3 shows another structural example of the main part of the optical limit switch including the pressure sensitive element and the pressure mechanism. In this example, the pressure sensitive element 11 and the pressure block 26 are made of rubber. It is arranged in a mold part 35 made of a plastic material, and the mold part 35 is fixed in a case 36 made of metal or the like. One end of a lever 37 is fixed to the mold portion 35, and the lever 37 is in contact with the pressure block 26. One end of a spring 38 is fixed to the case 36, and a movable block 39 fixed to the other end of the spring 38 is in contact with a free end of the lever 37. One end of a lever 40 is fixed to the movable block 39, and a roller 41 that constitutes an operating portion is attached to the other end of the lever 40.

In the example shown in FIG. 3, when a force is applied to the roller (operation unit) 41, the lever 40 bends and the operation unit 41 is displaced as shown by the chain line in the figure. At this time, the movable block 39 bends the lever 37, and the lever 37 presses the pressure block 26.

FIGS. 4 (A) and 4 (B) show another structural example of the main part including the pressurizing mechanism and the pressure sensitive element. In this example, a spring 51 is provided at the bottom of the case 50. The pressure sensitive element 11 is arranged on the supporting plate 52 supported by the pressure sensitive element 11. A pair of pressure blocks 53 and 54 are also disposed on the support plate 52, and these pressure blocks are in contact with the pressure surfaces 11c and 11d of the pressure sensitive element 11. One ends of levers 55 and 56 are pivotally supported by the pressure blocks 53 and 54, respectively, and the other ends of these levers are pivotally supported at corners at both ends of the bottom of the case 50. The end surfaces 53a, 54a of the pressure blocks 53, 54 opposite to the support plate 52 are formed in a spherical shape or a cylindrical surface shape, and the pressure plate 57 is in contact with the end surfaces of these pressure blocks. One end of the pressure block 58 is further brought into contact with the pressure plate 57, and the protrusion 58a provided at the other end of the pressure block 58 penetrates the end wall of the case 50 and is led to the outside. There is. An intermediate portion of a lever 59, one end of which is supported by a case 50 through a pin 60, is in contact with a protrusion 58a of the pressure block 58. A roller 61 that constitutes an operating portion is attached to the other end of the lever 59.

Further, in this example, the polarizer 18 and the analyzer 20 are brought into contact with the facing surface of the pressure sensitive element facing in a direction perpendicular to the facing direction of the pressure blocks 53 and 54, and the polarizer 18 and the detector 18 are detected. The optical fibers 17 and 21 respectively coupled to the photons 20 are led out of the case.

In the embodiment shown in FIG. 4, when the force f is applied to the roller 61 that constitutes the operation portion, the pressure blocks 53 and 54 are pressed via the pressure block 58. At this time, the pressure blocks 53 and 54 are displaced toward the bottom of the case 50 and toward each other, so that the pressure sensitive element 11 is pressed in the direction opposite to the pressure blocks 53 and 54. In this case, the smaller the inclination angle θ of the levers 55 and 56, the higher the pressure applied to the pressure sensitive element when an external force is applied to the lever 59.

FIG. 5 shows still another configuration example of the main part including the pressure mechanism and the pressure-sensitive element. In this example, the pressure-sensitive element formed in the case 60 in a cubic shape or a rectangular parallelepiped shape. 11, the pressure block 61 is in contact with one pressure surface 11c of the pressure sensitive element 11, and the other pressure surface 11d is in contact with the bottom portion of the case 60. In this example, one surface orthogonal to the facing direction of the pressure surfaces 11c and 11d of the pressure-sensitive element 11 is an entrance / exit surface 11a 'which also serves as an entrance surface and an exit surface, and the entrance / exit surface 11a' includes a polarizer and a detector. A polarizing plate 62 that also serves as a photon is opposed. The surface facing the entrance / exit surface 11a 'is a reflecting surface 11b', and a mirror 63 is formed on the reflecting surface 11b '. A protrusion 61a provided on the pressure block 61 penetrates the case 60 and is led to the outside, and a lever 64 having one end pivotally supported by the case 60 is in contact with the protrusion 61a. A roller 65 that constitutes an operating portion is attached to the other end of the lever 64. Light is given to the polarizing plate 62 through the optical fiber 17, and the light reflected by the mirror 63 and passing through the polarizing plate 62 is guided to the outside through the optical fiber 21.

In the embodiment shown in FIG. 5, light supplied from a light source (not shown) through the collimator and the optical fiber 17 enters the polarizing plate 62. At this time, the polarizing plate 62 acts as a polarizer and gives linearly polarized light to the pressure sensitive element 11. The linearly polarized light that has entered the pressure sensitive element 11 is reflected by the mirror 63 and enters the polarizing plate 62. At this time, the polarizing plate 62 acts as an analyzer, transmits the linearly polarized light component of the light reflected by the mirror 63, and gives the linearly polarized light component to the light receiving circuit (not shown) through the optical fiber 21. In the case of the configuration as in this example, the case where the polarizer and the analyzer are arranged so as to face each other with the respective polarization directions parallel to each other with the pressure sensitive element interposed therebetween by using only one polarizing plate. Similar characteristics (characteristics in FIG. 6B) can be obtained.

As described above, according to the present invention, it suffices to provide the pressure-sensitive element with the mechanism for transmitting the pressure through the lever, and does not need the mechanism having the sliding portion. Therefore, as shown in FIG. 2, FIG. 3 and FIG. 5, the pressure sensitive element and the light input portion and the light output portion are molded and sealed with a light-transmissive transparent rubber or plastics molding material. can do. In this case, since the molding material has a light-transmitting property, even if the molding material is filled between the polarizer and the pressure-sensitive element and between the analyzer and the pressure-sensitive element, no trouble will occur. .

Further, also in the example shown in FIG. 4, the case 50 can have a sealed structure. Therefore, dew condensation occurs on the main part of the switch including the pressure sensitive element, the polarizer and the analyzer, and the connection between the polarizer and the analyzer and the optical system on the input side and the optical system on the output side. It is possible to prevent the adhesion of the limit switch and prevent malfunction of the limit switch due to dew condensation or adhesion of dust, thereby improving reliability.

Further, if the main part is hermetically sealed, it is possible to prevent the deterioration of the performance due to the corrosion deterioration of the components of the optical system when used in an environment where there is a risk of coming into contact with corrosive gas. You can

In the above-described embodiment, light having a wavelength at which the polarizer and the analyzer do not function is used as the reference light, and the loss of the optical path is constantly monitored by the reference light, and the reference light, the polarizer and the analyzer are used. By performing a sensitivity correction calculation such as taking the ratio of the polarized wavelength to the optical output, the detection operation can be performed without being affected by the vibration and pressure of the optical fiber. You can For example, if the input light of wavelength λ1 which is not polarized by either the polarizer or the analyzer is Iλ1 and the modulation amount is α, the input light is not affected by the modulation amount, and the output light is also Iλ1. Here, if the coefficient representing the influence of disturbance such as vibration and pressure applied to the optical fiber is β, the final output is βI λ1. On the other hand, at the wavelength λ2 where the polarizer and the analyzer function, the light output Iλ2 of the wavelength λ2 is modulated by the modulation amount α, so the output light becomes αIλ2. Even in this case, the optical fiber is affected by vibrations and disturbances such as pressure. Therefore, if the coefficient representing the degree of the influence is β, the final optical output is αβIλ2. Here, if the ratio of αβIλ2 and βIλ1 is taken, αβIλ2 / βIλ1 = α (Iλ2 / Iλ1), and the influence of the disturbance β can be eliminated.

Although glass or plastic is used as the photoelastic material in the above description, the photoelastic material may be any material as long as it is light transmissive and has a photoelastic effect.

In the example shown in FIG. 1, in the light receiving device, the amount of received light is compared with the first determination value and the second determination value, and the range between the first determination value and the second determination value is set. Although it is configured so as to have a dead zone, it is not always necessary to configure in this way, and depending on the application of the switch, the received light amount is compared with a single judgment value, and the magnitude relationship between the received light amount and the judgment value is used. The position of the operation portion of the switch may be determined by discriminating the level of the received light amount.

In each of the above embodiments, the end of the optical fiber on the input side is directly opposed to the polarizer. However, if necessary, a parallel light beam may be provided between the end of the optical fiber and the polarizer. It is also possible to provide an optical element such as an optical element (collimator) for obtaining Similarly, an optical element such as a collimator can be provided between the analyzer and the end of the optical fiber on the output side. It is also possible to provide a condenser lens between the analyzer and the end of the optical fiber on the output side.

[0040]

[Effect of device]

 As described above, according to the present invention, the force acting on the operating portion is transmitted to the pressure-sensitive element made of a photoelastic material through the lever so that the pressure-sensitive element can be operated with a pressure corresponding to the displacement amount of the operating portion. Since the light that has been pressurized and transmitted through the polarizer and the pressure sensitive element is detected through the analyzer, the amount of light detected through the analyzer can be changed according to the amount of displacement of the operation unit. Therefore, by discriminating the level of the amount of light detected through the analyzer by the light receiving device, it is possible to obtain a signal indicating that the mover is in a predetermined position, and perform the same detection operation as a conventional limit switch. Can be made. Further, according to the present invention, a mechanism for transmitting the force acting on the operation portion to the pressure sensitive element via the lever may be provided, and a mechanical sliding portion need not be provided. It is possible to prevent damage to the target part and prolong the service life.

Further, according to the invention described in claim 3, since it is possible to prevent water and dust from adhering to the main part of the switch, it is possible to always ensure the operation and enhance the reliability.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a sectional view showing a structural example of a main part of an optical limit switch according to the present invention.

FIG. 3 is a sectional view showing another structural example of the main part of the optical limit switch according to the present invention.

FIG. 4A is a sectional view showing still another configuration example of the main part of the optical limit switch according to the present invention. (B)
FIG. 7B is a sectional view taken along line BB of FIG.

FIG. 5 is a sectional view showing still another configuration example of the main part of the optical limit switch according to the present invention.

FIG. 6 shows the relationship between the output light quantity and the applied pressure in the optical limit switch according to the present invention. (A) and (B) show the case where the polarizer and the analyzer are arranged in a cross and the case where they are arranged in parallel. It is the diagram which showed an example of the output light quantity-pressure characteristic in the case.

7A and 7B are respectively applied to an output light quantity and a pressure-sensitive element when a polarizer and an analyzer are arranged in a cross arrangement and in a parallel arrangement in an optical limit switch according to the present invention. It is the diagram which showed the relationship with a force using stress as a parameter. (C) is a perspective view showing the positional relationship among the pressure sensitive element, the polarizer, the analyzer, and the optical fiber when obtaining the characteristics of (A) and (B).

FIG. 8 is a sectional view showing a configuration of a conventional optical limit switch.

[Explanation of symbols]

 11 Pressure Sensing Element 12 Pressurizing Mechanism 13 Optical Input Section, 14 Light Source 17 Optical Fiber 18 Polarizer 19 Optical Output Section 20 Analyzer 24 Photoreceptor 26 Pressing Block 28 Lever 29 Contactor 29a Operating Unit 37 Lever 41 Roller (Operating Unit) ) 53, 54 pressure block 55, 56 lever 57 pressure plate 58 pressure block 59 lever 61 roller (operation unit) 61 pressure block 62 polarizing plate that also serves as a polarizer and analyzer 63 mirror

Claims (3)

[Scope of utility model registration request] 1. A pressure-sensitive element made of a photoelastic material, and an external force applied to an operating portion is transmitted to the pressure-sensitive element via a lever, and the pressure-sensitive element is pressured according to a displacement amount of the operating portion. A pressure mechanism for applying pressure, a light input section for making light incident on the pressure sensitive element through a polarizer, a light output section for emitting light transmitted through the pressure sensitive element through an analyzer, and a light output section from the light output section. An optical limit switch, comprising: a light receiving device that discriminates the amount of emitted light and generates a detection output indicating that the operating portion is at a predetermined position. 2. The light receiving device, wherein a light receiving circuit for converting the light emitted from the light output section into an electric signal, a first judgment value for the electric signal, and a value higher than the first judgment value are set. And a comparison circuit for comparing with the second judgment value,
The first detection output is generated when the electric signal is lower than the first judgment value, and the second detection output is generated when the electric signal is higher than the second judgment value. Optical limit switch described in 1. 3. The optical limit switch according to claim 1, wherein the pressure sensitive element and the light input portion and the light output portion are covered with a molding material and sealed.