A pressure sensor based on large-core plastic optical fiber for a circuit board disassembly and crushing device and its usage method

Abstract

The present invention discloses a pressure sensor based on a large-core plastic optical fiber and its usage method for a circuit board disassembly and crushing device, belonging to the technical field of circuit board disassembly and crushing. The optical output end of a light source is connected to the optical input end of the large-core plastic optical fiber, the optical output end of the large-core plastic optical fiber is connected to the optical input end of a photodetector, the electrical output end of the photodetector is connected to the electrical input end of a processing system, the electrical output end of the processing system outputs the output signal of the liquid pressure sensor based on the large-core plastic optical fiber, and a fiber defect is axially provided on one side of the middle section of the large-core plastic optical fiber. The fiber defect is sealed with a fiber defect cover, and a cover hole is provided at the center of the fiber defect cover corresponding to the fiber defect. The present invention has the advantages of simple structure, small volume, low cost, anti-electromagnetic interference, and small influence of temperature, and can stably measure the pressure of hydraulic oil.

Description

Technical Field

[0001] The present invention relates to a pressure sensor based on a large-core plastic optical fiber and a method for using the same for a circuit board disassembly and crushing device, belonging to the technical field of circuit board disassembly and crushing. Background Art

[0002] In existing circuit board disassembly and crushing devices, a hydraulic system is generally used as the driving power source for the circuit board disassembly and crushing device. The hydraulic system uses hydraulic oil as the working medium. Among them, the flow rate of the hydraulic oil is not large but the pressure is high. In order to monitor the pressure of the hydraulic oil in real time and avoid usage accidents, a liquid pressure sensor needs to be placed in the hydraulic oil.

[0003] A liquid pressure sensor is an instrument for measuring liquid pressure and is of great significance to people's life and production. A liquid pressure sensor is one of the most commonly used pressure sensors in industrial practice and is widely used in various industrial automatic control environments, such as on-site measurement and control of industrial processes in industries such as oil pipelines, water conservancy and hydropower, railway transportation, intelligent buildings, aerospace, hydraulic machinery, military industry, oil wells, electric power, ships, machine tools, heat, and metallurgy. Currently, the more widely used liquid pressure sensor is made by encapsulating an isolated silicon piezoresistive pressure-sensitive element in a stainless steel shell. Through the internal strain structure and circuit system, the liquid pressure it senses is converted into a corresponding electrical signal for external output and the liquid pressure is displayed.

[0004] However, the current liquid pressure sensor has a complex strain structure and circuit system, is easily affected by various factors and has poor stability, such as pressure disturbances in the measured environment, voltage fluctuations inside the sensor, circuit system aging, etc., and is extremely vulnerable to the influence of electromagnetic fields and temperature in the environment, resulting in a complex structure, large volume, low accuracy, poor adaptability, high manufacturing difficulty, susceptibility to electromagnetic interference, and poor temperature stability of the liquid pressure sensor.

[0005] Therefore, the existing liquid pressure sensors are not suitable for being placed in hydraulic oil for use. Summary of the Invention

[0006] The present invention proposes a pressure sensor based on a large-core plastic optical fiber and a method for using the same for a circuit board disassembly and crushing device to solve the problems of the current liquid pressure sensor having a complex structure, large volume, low accuracy, high manufacturing difficulty, susceptibility to electromagnetic and temperature influences, and not being suitable for being placed in hydraulic oil for use.

[0007] A pressure sensor based on a large-core plastic optical fiber for a circuit board disassembly and crushing device. The liquid pressure sensor based on a large-core plastic optical fiber includes a light source, a large-core plastic optical fiber, an optical fiber defect sheath, a photodetector, and a processing system. The light output end of the light source is connected to the light input end of the large-core plastic optical fiber. The light output end of the large-core plastic optical fiber is connected to the light input end of the photodetector. The electrical output end of the photodetector is connected to the electrical input end of the processing system. The electrical output end of the processing system outputs the output signal of the liquid pressure sensor based on the large-core plastic optical fiber.

[0008] An optical fiber defect is axially provided on one side of the middle section of the large-core plastic optical fiber. The optical fiber defect sheath covers the optical fiber defect, and a sheath small hole is provided at the center of the optical fiber defect sheath corresponding to the optical fiber defect.

[0009] Furthermore, the length of the optical fiber defect is much smaller than the total length of the large-core plastic optical fiber. The depth W of the optical fiber defect is less than the diameter of the large-core plastic optical fiber and greater than the radius of the large-core plastic optical fiber.

[0010] Furthermore, when the large-core plastic optical fiber is immersed in hydraulic oil, the optical fiber defect includes a first section of air, the measured hydraulic oil, and a second section of air. The first section of air and the second section of air are located at both ends of the optical fiber defect, and the measured hydraulic oil is located at the sheath small hole.

[0011] The optical fiber defect sheath (3) covers the optical fiber defect in the middle of the large-core plastic optical fiber (2), sealing the first section of air (4) and the second section of air (7) at both ends of the optical fiber defect in the middle of the large-core plastic optical fiber (2) respectively.

[0012] Furthermore, when the pressure of the hydraulic oil changes, the optical fiber defect sheath has no deformation.

[0013] Furthermore, the measured hydraulic oil is communicated with the external hydraulic oil through the sheath small hole, and the measured hydraulic oil flows freely through the sheath small hole.

[0014] Furthermore, the refractive index of the large-core plastic optical fiber is greater than the refractive index of the measured hydraulic oil.

[0015] The refractive index of the large-core plastic optical fiber is much greater than the change amount of the refractive index of the measured hydraulic oil under the condition of unit temperature change, and the change amount of the refractive index of the large-core plastic optical fiber under the condition of unit temperature change is much less than the refractive index of the measured liquid.

[0016] The refractive index of the first section of air is less than the refractive index of the measured hydraulic oil.

[0017] The refractive index of the second section of air is less than the refractive index of the measured hydraulic oil.

[0018] The first section of air, the hydraulic oil to be measured, and the second section of air. The phase of the light after passing through these three is P1, and the phase of the light after passing through the large-core plastic optical fiber for a distance L is P2. Then, P2 - P1 < π is satisfied.

[0019] The transmittance of the output light of the light source after passing through the first section of air, the hydraulic oil, and the second section of air is greater than 50%.

[0020] Furthermore, the instantaneous power of the output light of the light source is constant at different times, and the coherence length of the output light of the light source is much greater than the length of the optical fiber defect.

[0021] Furthermore, the processing system includes an acquisition circuit, a filtering circuit, and an analysis and output circuit. The electrical input terminal of the acquisition circuit serves as the electrical input terminal of the processing system, and the electrical output terminal of the analysis and output circuit is the electrical output terminal of the processing system. The electrical output terminal of the photodetector is connected to the electrical input terminal of the acquisition circuit, the electrical output terminal of the acquisition circuit is connected to the electrical input terminal of the filtering circuit, the electrical output terminal of the filtering circuit is connected to the electrical input terminal of the analysis and output circuit, and the electrical output terminal of the analysis and output circuit outputs the sensor output signal.

[0022] A method for using a pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device. Based on the above-mentioned pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device, the method for using the pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device includes the following steps:

[0023] S100: Immerse the optical fiber defect on the large-core plastic optical fiber under the liquid level of the hydraulic oil and move it to the position to be measured.

[0024] S200: Turn on the light source, the photodetector, and the processing system.

[0025] S300: The photodetector converts the output light of the large-core plastic optical fiber into an electrical signal of corresponding intensity and outputs it to the processing system. The processing system obtains the pressure of the hydraulic oil according to the electrical signal.

[0026] Furthermore, in S200, let the length of the first section of air be L4, the length of the second section of air be L7, the length of the hydraulic oil to be measured be L5, and the length of the optical fiber defect along the central axis direction of the large-core plastic optical fiber be L. Then, L4 + L5 + L7 = L. The light passing through the first section of air, the hydraulic oil to be measured, and the second section of air is the second part of the light, and the rest of the light is the first part of the light. Specifically,

[0027] When the pressure of the hydraulic oil increases, the hydraulic oil flows into the optical fiber defect through the skin small hole in the middle of the optical fiber defect skin. The length L5 of the measured hydraulic oil increases, the length L4 of the first section of air decreases, and the length L7 of the second section of air decreases, but still satisfies L4 + L5 + L7 = L; the optical path of the second part of the light after being transmitted through the first section of air, the measured hydraulic oil and the second section of air increases, and the phase of the second part of the light after being transmitted through the first section of air, the measured hydraulic oil and the second section of air also increases accordingly; when the first part of the light meets the second part of the light, the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light decreases, and the intensity of the interference light generated by the interference of the first part of the light and the second part of the light increases;

[0028] When the pressure of the hydraulic oil decreases, the measured hydraulic oil flows out of the optical fiber defect through the skin small hole in the middle of the optical fiber defect skin. The length L5 of the measured hydraulic oil decreases, the length L4 of the first section of air increases, and the length L7 of the second section of air increases, but still satisfies L4 + L5 + L7 = L; the optical path of the second part of the light after being transmitted through the first section of air, the measured hydraulic oil and the second section of air decreases, and the phase of the second part of the light after being transmitted through the first section of air, the measured hydraulic oil and the second section of air also decreases accordingly; when the first part of the light meets the second part of the light, the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light increases, and the intensity of the interference light generated by the interference of the first part of the light and the second part of the light decreases.

[0029] The beneficial effects of the present invention: A pressure sensor based on a large-core plastic optical fiber and its usage method applied to a circuit board disassembly and crushing device of the present invention includes a large-core plastic optical fiber with a defect. The measured hydraulic oil is introduced at the defect of the plastic optical fiber, so that at the defect of the plastic optical fiber, an open section of the measured hydraulic oil and two sections of sealed air are formed. When the pressure of the measured hydraulic oil changes, it will cause changes in the length of the measured hydraulic oil and the lengths of the two sections of air at the defect of the plastic optical fiber, thereby changing the optical path of the light passing through the defect of the plastic optical fiber, and finally causing changes in the output light intensity of the optical fiber. Therefore, the present invention has the advantages of simple structure, small volume, low cost, anti-electromagnetic interference, and small influence of temperature. Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of a pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device of the present invention;

[0031] Figure 2 It is a schematic structural diagram of the processing system.

[0032] Among them, 1 is a light source, 2 is a large-core plastic optical fiber, 3 is an optical fiber defect sheath, 4 is the first section of air, 5 is the hydraulic oil to be measured, 6 is a sheath small hole, 7 is the second section of air, 8 is a photodetector, 9 is a processing system, 9-1 is an acquisition circuit, 9-2 is a filtering circuit, and 9-3 is an analysis and output circuit. Specific embodiments

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Refer to Figure 1 - Figure 2 As shown, the present invention proposes a pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device. The liquid pressure sensor based on a large-core plastic optical fiber includes a light source 1, a large-core plastic optical fiber 2, an optical fiber defect sheath 3, a photodetector 8, and a processing system 9. The light output end of the light source 1 is connected to the light input end of the large-core plastic optical fiber 2, the light output end of the large-core plastic optical fiber 2 is connected to the light input end of the photodetector 8, the electrical output end of the photodetector 8 is connected to the electrical input end of the processing system 9, and the electrical output end of the processing system 9 outputs the output signal of the liquid pressure sensor based on the large-core plastic optical fiber.

[0035] One side of the middle section of the large-core plastic optical fiber 2 is axially provided with an optical fiber defect, and the optical fiber defect sheath 3 covers the optical fiber defect, and a sheath small hole 6 is provided at the center of the optical fiber defect sheath 3 corresponding to the optical fiber defect.

[0036] Specifically, the present invention includes a large-core plastic optical fiber 2 with a defect. The hydraulic oil to be measured is introduced into the optical fiber defect of the large-core plastic optical fiber 2, so that an open section of the hydraulic oil to be measured and two sealed sections of air are formed at the optical fiber defect of the plastic optical fiber. When the pressure of the hydraulic oil to be measured changes, it will cause changes in the lengths of the hydraulic oil to be measured and the two sections of air at the optical fiber defect of the plastic optical fiber, thereby changing the optical path of the light passing through the optical fiber defect, and finally changing the output light intensity of the optical fiber, so as to realize the detection of pressure. Therefore, the present invention has the advantages of simple structure, small volume, low cost, anti-electromagnetic interference, and small influence of temperature.

[0037] The contact part between the optical fiber defect sheath 3 and the large-core plastic optical fiber 2 is sealed, that is, only the inside and outside of the optical fiber defect are connected through the sheath small hole 6.

[0038] Furthermore, the length of the optical fiber defect is much smaller than the total length of the large-core plastic optical fiber 2, and the depth W of the optical fiber defect is less than the diameter of the large-core plastic optical fiber 2 and greater than the radius of the large-core plastic optical fiber 2.

[0039] Furthermore, when the large-core plastic optical fiber 2 is immersed in hydraulic oil, the optical fiber defect includes a first section of air 4, the hydraulic oil to be measured 5, and a second section of air 7. The first section of air 4 and the second section of air 7 are located at both ends of the optical fiber defect, and the hydraulic oil to be measured 5 is located at the skin small hole 6.

[0040] The optical fiber defect skin 3 covers the optical fiber defect in the middle of the large-core plastic optical fiber 2, and seals the first section of air 4 and the second section of air 7 at both ends of the optical fiber defect in the middle of the large-core plastic optical fiber 2 respectively;

[0041] Specifically, the refractive index of the large-core plastic optical fiber 2 is greater than the refractive index of the hydraulic oil to be measured, and the refractive index of the large-core plastic optical fiber 2 is much greater than the change amount of the refractive index of the hydraulic oil to be measured under the condition of unit temperature change (that is, the change amount of the refractive index of the hydraulic oil to be measured when the temperature changes by 1 degree Celsius), and the change amount of the refractive index of the large-core plastic optical fiber 2 under the condition of unit temperature change (that is, the change amount of the refractive index of the large-core plastic optical fiber 2 when the temperature changes by 1 degree Celsius) is much less than the refractive index of the hydraulic oil to be measured;

[0042] Furthermore, when the pressure of the hydraulic oil changes, the optical fiber defect skin 3 has no deformation.

[0043] Furthermore, the hydraulic oil to be measured 5 is communicated with the external hydraulic oil through the skin small hole 6, and the hydraulic oil to be measured 5 flows freely through the skin small hole 6.

[0044] Furthermore, the refractive index of the large-core plastic optical fiber 2 is greater than the refractive index of the hydraulic oil to be measured 5;

[0045] The refractive index of the large-core plastic optical fiber 2 is much greater than the change amount of the refractive index of the hydraulic oil to be measured 5 under the condition of unit temperature change, and the change amount of the refractive index of the large-core plastic optical fiber 2 under the condition of unit temperature change is much less than the refractive index of the measured liquid;

[0046] The refractive index of the first section of air 4 is less than the refractive index of the hydraulic oil to be measured 5;

[0047] The refractive index of the second section of air 7 is less than the refractive index of the hydraulic oil to be measured 5;

[0048] For the first section of air 4, the hydraulic oil to be measured 5, and the second section of air 7, the phase of the light after being transmitted through the three is P1, and the phase of the light after being transmitted through the large-core plastic optical fiber 2 for a distance L is P2, then P2 - P1 < π is satisfied;

[0049] The transmittance of the output light of the light source 1 after being transmitted through the first section of air 4, hydraulic oil 5, and the second section of air 7 is greater than 50%.

[0050] Furthermore, the instantaneous power of the output light of the light source 1 remains constant at different times, and the coherence length of the output light of the light source 1 is much greater than the length of the optical fiber defect.

[0051] Furthermore, the processing system 9 includes an acquisition circuit 9-1, a filtering circuit 9-2, and an analysis and output circuit 9-3. The electrical input terminal of the acquisition circuit 9-1 serves as the electrical input terminal of the processing system 9, and the electrical output terminal of the analysis and output circuit 9-3 is the electrical output terminal of the processing system 9; the electrical output terminal of the photodetector 8 is connected to the electrical input terminal of the acquisition circuit 9-1, the electrical output terminal of the acquisition circuit 9-1 is connected to the electrical input terminal of the filtering circuit 9-2, the electrical output terminal of the filtering circuit 9-2 is connected to the electrical input terminal of the analysis and output circuit 9-3, and the electrical output terminal of the analysis and output circuit 9-3 outputs the sensor output signal.

[0052] Specifically, the photodetector 8 converts the optical signal into a voltage signal and sends it to the acquisition circuit 9-1. The acquisition circuit 9-1 acquires the voltage signal sent by the photodetector 8 and sends this voltage signal to the filtering circuit 9-2. The filtering circuit 9-2 performs high-frequency filtering on the voltage signal to remove the high-frequency noise in the voltage signal. Then, the filtering circuit 9-2 sends the filtered voltage signal to the analysis and output circuit 9-3. The analysis and output circuit 9-3 obtains the voltage value of the filtered voltage signal and calculates the pressure of the measured hydraulic oil 5 from this voltage value. Finally, the analysis and output circuit 9-3 outputs the sensor output signal, and the sensor output signal includes the pressure of the measured hydraulic oil 5.

[0053] A method for using a pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device. Based on the above-mentioned pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device, the method for using the pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device includes the following steps:

[0054] S100: Immerse the optical fiber defect on the large-core plastic optical fiber 2 under the liquid level of the hydraulic oil and move it to the position to be measured;

[0055] S200: Turn on the light source 1, the photodetector 8, and the processing system 9;

[0056] S300: The photodetector 8 converts the output light of the large-core plastic optical fiber 2 into an electrical signal of corresponding intensity and outputs it to the processing system 9. The processing system 9 obtains the pressure of the hydraulic oil based on the electrical signal.

[0057] Further, in S200, let the length of the first section of air 4 be L4, the length of the second section of air 7 be L7, the length of the hydraulic oil 5 to be measured be L5, and the length of the optical fiber defect along the central axis direction of the large-core plastic optical fiber 2 be L. Then L4 + L5 + L7 = L. The light passing through the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7 is the second part of the light, and the rest of the light is the first part of the light. For the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7, the phase of the second part of the light is P1, and the phase of the first part of the light after transmitting a distance L through the large-core plastic optical fiber 2 is P2, and P2 - P1 < π.

[0058] Specifically,

[0059] When the pressure of the hydraulic oil increases, the hydraulic oil flows into the optical fiber defect through the skin holes 6 in the middle of the optical fiber defect skin 3. The length L5 of the hydraulic oil 5 to be measured increases, the length L4 of the first section of air 4 decreases, and the length L7 of the second section of air 7 decreases, but still satisfies L4 + L5 + L7 = L; the optical path of the second part of the light after transmitting through the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7 increases, and the phase of the second part of the light after transmitting through the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7 also increases accordingly; when the first part of the light meets the second part of the light, the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light decreases, and the intensity of the interference light generated by the interference of the first part of the light and the second part of the light increases;

[0060] When the pressure of the hydraulic oil decreases, the hydraulic oil 5 to be measured flows out of the optical fiber defect through the skin holes 6 in the middle of the optical fiber defect skin 3. The length L5 of the hydraulic oil 5 to be measured decreases, the length L4 of the first section of air 4 increases, and the length L7 of the second section of air 7 increases, but still satisfies L4 + L5 + L7 = L; the optical path of the second part of the light after transmitting through the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7 decreases, and the phase of the second part of the light after transmitting through the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7 also decreases accordingly; when the first part of the light meets the second part of the light, the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light increases, and the intensity of the interference light generated by the interference of the first part of the light and the second part of the light decreases.

[0061] Specifically, in the middle of the large-core plastic optical fiber 2, an optical fiber defect is formed by removing most of the plastic optical fiber on one side. The optical fiber defect skin 3 is closely attached to the outer surface of the large-core plastic optical fiber 2 and covers the optical fiber defect, so that the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7 are formed at the optical fiber defect, and the first section of air 4 and the second section of air 7 are respectively sealed at both ends of the optical fiber defect. The first section of air 4 and the second section of air 7 are separated by the hydraulic oil 5 to be measured; the skin holes 6 are located in the middle of the optical fiber defect skin 3;

[0062] The output light of the light source 1 enters the large-core plastic optical fiber 2. Since the refractive index of the large-core plastic optical fiber 2 is greater than that of the measured hydraulic oil, for the light that satisfies the total reflection condition at the interface between the large-core plastic optical fiber 2 and the measured hydraulic oil, it will be confined inside the large-core plastic optical fiber 2 and transmitted along the large-core plastic optical fiber 2;

[0063] When the light is transmitted to the optical fiber defect in the middle of the large-core plastic optical fiber 2, it will be divided into two parts of light with different transmission paths. The first part of the light is transmitted through the plastic optical fiber that has not been removed beside the optical fiber defect, and the second part of the light is transmitted through the first section of air 4, the measured hydraulic oil 5, and the second section of air 7. After the two parts of light are transmitted through the optical fiber defect, they meet again in the large-core plastic optical fiber 2. Since the length L of the optical fiber defect in the middle of the large-core plastic optical fiber 2 is much smaller than the total length of the large-core plastic optical fiber 2, and the coherence length of the output light of the light source 1 is much greater than the length L of the optical fiber defect in the middle of the large-core plastic optical fiber 2, when the first part of the light meets the second part of the light, the two parts of light interfere and generate interference light;

[0064] The interference light is output from the large-core plastic optical fiber 2 and then enters the photodetector 8. The photodetector 8 converts the optical signal into a voltage signal and sends it to the processing system 9. The processing system 9 performs voltage signal acquisition, filtering, data analysis, and finally outputs the sensor output signal. The sensor output signal contains the pressure of the measured hydraulic oil;

[0065] Since the depth W of the optical fiber defect is less than the diameter of the large-core plastic optical fiber 2 and greater than the radius of the large-core plastic optical fiber 2, and at the same time, the transmittance of the output light of the light source 1 after being transmitted through the first section of air 4, the measured hydraulic oil 5, and the second section of air 7 is greater than 50%, the intensity of the first part of the light is similar to that of the second part of the light. In this way, the intensity of the interference light significantly depends on the phase difference between the first part of the light and the second part of the light;

[0066] Since the refractive index of the large-core plastic optical fiber 2 is greater than that of the measured hydraulic oil, the refractive index of the first section of air 4 is less than that of the measured hydraulic oil, and the refractive index of the second section of air 7 is less than that of the measured hydraulic oil, when the first part of the light meets the second part of the light, the phase of the first part of the light is greater than the phase of the second part of the light; since the phase of the first part of the light after being transmitted through the large-core plastic optical fiber 2 for a distance L is P2, and the phase of the second part of the light after being transmitted through the first section of air 4, the measured hydraulic oil 5, and the second section of air 7 is P1, and P2 - P1 < π, when the first part of the light meets the second part of the light, the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light is less than π;

[0067] When measuring the pressure at different positions of the measured hydraulic oil in the present invention, the cover hole 6 needs to be placed at the position to be measured in the measured hydraulic oil;

[0068] Since the hydraulic oil to be measured can flow freely through the sheath small hole 6 in the middle of the optical fiber defect sheath 3, the hydraulic oil 5 to be measured is connected to the external hydraulic oil to be measured through the sheath small hole 6. Therefore, when the pressure of the hydraulic oil to be measured changes, the following two situations will occur:

[0069] (1) When the pressure of the hydraulic oil to be measured increases, the hydraulic oil to be measured flows into the optical fiber defect through the sheath small hole 6 in the middle of the optical fiber defect sheath 3. Since the optical fiber defect sheath 3 does not deform when the pressure of the hydraulic oil to be measured changes, the length L5 of the hydraulic oil 5 to be measured increases, the length L4 of the first section of air 4 decreases, and the length L7 of the second section of air 7 decreases, but still satisfies L4 + L5 + L7 = L; since the refractive index of the first section of air 4 is less than the refractive index of the hydraulic oil to be measured, and the refractive index of the second section of air 7 is less than the refractive index of the hydraulic oil to be measured, the optical path of the second part of the light transmitted through the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7 increases, and the phase of the second part of the light transmitted through the first section of air 4, the hydraulic oil 5 to be measured, and the second section of air 7 also increases accordingly; since when the first part of the light meets the second part of the light, the phase of the first part of the light is greater than the phase of the second part of the light, when the first part of the light meets the second part of the light, the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light decreases; since the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light is less than π, and the instantaneous power of the output light of the light source 1 is constant at different times, when the first part of the light meets the second part of the light, the intensity of the interference light generated by the interference of the two parts of the light increases;

[0070] (2) When the pressure of the hydraulic oil to be measured decreases, the hydraulic oil to be measured flows out of the optical fiber defect through the skin small hole 6 in the middle of the optical fiber defect skin 3. Since the optical fiber defect skin 3 does not deform when the pressure of the hydraulic oil to be measured changes, therefore, the length L5 of the hydraulic oil to be measured 5 decreases, the length L4 of the first section of air 4 increases, and the length L7 of the second section of air 7 increases, but still satisfies L4 + L5 + L7 = L; since the refractive index of the first section of air 4 is less than the refractive index of the hydraulic oil to be measured, and the refractive index of the second section of air 7 is less than the refractive index of the hydraulic oil to be measured, therefore, the optical path of the second part of light after being transmitted through the first section of air 4, the hydraulic oil to be measured 5 and the second section of air 7 decreases, and the phase of the second part of light after being transmitted through the first section of air 4, the hydraulic oil to be measured 5 and the second section of air 7 also decreases accordingly; since when the first part of light meets the second part of light, the phase of the first part of light is greater than the phase of the second part of light, therefore, when the first part of light meets the second part of light, the phase difference obtained by subtracting the phase of the second part of light from the phase of the first part of light increases; since the phase difference obtained by subtracting the phase of the second part of light from the phase of the first part of light is less than π, and the instantaneous power of the output light of the light source 1 is constant at different times, therefore, when the first part of light meets the second part of light, the intensity of the interference light generated by the interference of the two parts of light decreases;

[0071] In this way, the pressure of the hydraulic oil to be measured can be obtained from the intensity of the interference light, that is, the intensity of the output light of the large-core plastic optical fiber 2.

[0072] The output light of the large-core plastic optical fiber 2 enters the photodetector 8. The photodetector 8 converts the optical signal into a voltage signal and sends it to the processing system 9. The processing system 9 collects and filters the voltage signal, then obtains the voltage value of the voltage signal, and obtains the pressure of the hydraulic oil to be measured from the voltage value. Finally, the processing system 9 outputs the sensor output signal, and the sensor output signal includes the pressure of the hydraulic oil to be measured.

[0073] Since the refractive index of the large-core plastic optical fiber 2 is much larger than the change amount of the refractive index of the hydraulic oil to be measured under the condition of unit temperature change (that is, the change amount of the refractive index of the hydraulic oil to be measured per 1 degree Celsius temperature change), and the change amount of the refractive index of the large-core plastic optical fiber 2 under the condition of unit temperature change (that is, the change amount of the refractive index of the large-core plastic optical fiber 2 per 1 degree Celsius temperature change) is much less than the refractive index of the hydraulic oil to be measured, therefore, the influence of temperature on the total reflection at the interface between the large-core plastic optical fiber 2 and the hydraulic oil to be measured is very small. That is to say, when light is transmitted inside the large-core plastic optical fiber 2, it is hardly affected by temperature; combined with the above working principle of the present invention, it can be concluded that when the present invention measures the liquid pressure, it is hardly affected by temperature.

Claims

1. A pressure sensor based on large-core plastic optical fiber for a circuit board disassembly and crushing device, characterized in that, The liquid pressure sensor based on a large-core plastic optical fiber includes a light source (1), a large-core plastic optical fiber (2), an optical fiber defect sheath (3), a photodetector (8), and a processing system (9). The optical output end of the light source (1) is connected to the optical input end of the large-core plastic optical fiber (2), the optical output end of the large-core plastic optical fiber (2) is connected to the optical input end of the photodetector (8), the electrical output end of the photodetector (8) is connected to the electrical input end of the processing system (9), and the electrical output end of the processing system (9) outputs the output signal of the liquid pressure sensor based on the large-core plastic optical fiber. One side of the middle section of the large-core plastic optical fiber (2) is axially provided with an optical fiber defect. The optical fiber defect sheath (3) covers the optical fiber defect, and a sheath small hole (6) is provided at the center of the optical fiber defect sheath (3) corresponding to the optical fiber defect. When the large-core plastic optical fiber (2) is immersed in hydraulic oil, the optical fiber defect includes a first section of air (4), the measured hydraulic oil (5), and a second section of air (7). The first section of air (4) and the second section of air (7) are located at both ends of the optical fiber defect, and the measured hydraulic oil (5) is located at the sheath small hole (6). The optical fiber defect sheath (3) covers the optical fiber defect in the middle of the large-core plastic optical fiber (2), and seals the first section of air (4) and the second section of air (7) at both ends of the optical fiber defect in the middle of the large-core plastic optical fiber (2) respectively.

2. The pressure sensor based on a large-core plastic optical fiber applied to the circuit board disassembly and crushing device according to claim 1, wherein, The length of the optical fiber defect is much smaller than the total length of the large-core plastic optical fiber (2), and the depth W of the optical fiber defect is less than the diameter of the large-core plastic optical fiber (2) and greater than the radius of the large-core plastic optical fiber (2).

3. The pressure sensor based on a large-core plastic optical fiber applied to the circuit board disassembly and crushing device according to claim 1, characterized in that, When the pressure of the hydraulic oil changes, the optical fiber defect sheath (3) has no deformation.

4. The pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device according to claim 3, characterized in that, The measured hydraulic oil (5) is communicated with the external hydraulic oil through the sheath small hole (6), and the measured hydraulic oil (5) flows freely through the sheath small hole (6).

5. The pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device according to claim 4, characterized in that The refractive index of the large-core plastic optical fiber (2) is greater than the refractive index of the measured hydraulic oil (5). The change amount of the refractive index of the large-core plastic optical fiber (2) under the condition of unit temperature change is much greater than the change amount of the refractive index of the measured hydraulic oil (5) under the condition of unit temperature change, and the change amount of the refractive index of the large-core plastic optical fiber (2) under the condition of unit temperature change is much less than the refractive index of the measured liquid. The refractive index of the first section of air (4) is less than the refractive index of the measured hydraulic oil (5). The refractive index of the second section of air (7) is less than the refractive index of the measured hydraulic oil (s5). For the first section of air (4), the measured hydraulic oil (5), and the second section of air (7), if the phase of the light transmitted through the three is P1 and the phase of the light transmitted through the large-core plastic optical fiber (2) for a distance L is P2, then P2 - P1 < π is satisfied. The transmittance of the output light of the light source (1) after being transmitted through the first section of air (4), the measured hydraulic oil (5), and the second section of air (7) is greater than 50%.

6. The pressure sensor based on a large-core plastic optical fiber applied to the circuit board disassembly and crushing device according to claim 5, characterized in that, The instantaneous power of the output light of the light source (1) is constant at different times, and the coherence length of the output light of the light source (1) is much greater than the length of the optical fiber defect.

7. The pressure sensor based on a large-core plastic optical fiber for a circuit board disassembly and crushing device according to claim 6, characterized in that, The processing system (9) includes a collection circuit (9-1), a filtering circuit (9-2), and an analysis and output circuit (9-3). The electrical input terminal of the collection circuit (9-1) serves as the electrical input terminal of the processing system (9), and the electrical output terminal of the analysis and output circuit (9-3) is the electrical output terminal of the processing system (9); the electrical output terminal of the photodetector (8) is connected to the electrical input terminal of the collection circuit (9-1), the electrical output terminal of the collection circuit (9-1) is connected to the electrical input terminal of the filtering circuit (9-2), the electrical output terminal of the filtering circuit (9-2) is connected to the electrical input terminal of the analysis and output circuit (9-3), and the electrical output terminal of the analysis and output circuit (9-3) outputs a sensor output signal.

8. A method for using a pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device. Based on the pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device according to any one of claims 1-7, it is characterized in that, The method for using the pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device includes the following steps: S100: Immerse the optical fiber defect on the large-core plastic optical fiber (2) below the liquid level of the hydraulic oil and move it to the position to be measured. S200: Turn on the light source (1), the photodetector (8), and the processing system (9). S300: The photodetector (8) converts the output light of the large-core plastic optical fiber (2) into an electrical signal with a corresponding intensity and outputs it to the processing system (9), and the processing system (9) obtains the pressure of the hydraulic oil according to the electrical signal.

9. The usage method of a pressure sensor based on a large-core plastic optical fiber applied to a circuit board disassembly and crushing device according to claim 8, characterized in that, In S200, let the length of the first section of air (4) be L4, the length of the second section of air (7) be L7, the length of the measured hydraulic oil (5) be L5, and the length of the optical fiber defect along the central axis direction of the large-core plastic optical fiber (2) be L. Then L4 + L5 + L7 = L. The light passing through the first section of air (4), the measured hydraulic oil (5), and the second section of air (7) is the second part of the light, and the rest of the light is the first part of the light. Specifically, When the pressure of the hydraulic oil increases, the hydraulic oil flows into the optical fiber defect through the skin holes (6) in the middle of the optical fiber defect skin (3). The length L5 of the measured hydraulic oil (5) increases, the length L4 of the first section of air (4) decreases, and the length L7 of the second section of air (7) decreases, but still satisfies L4 + L5 + L7 = L; the optical path of the second part of the light transmitted through the first section of air (4), the measured hydraulic oil (5), and the second section of air (7) increases, and the phase of the second part of the light transmitted through the first section of air (4), the measured hydraulic oil (5), and the second section of air (7) also increases accordingly; when the first part of the light meets the second part of the light, the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light decreases, and the intensity of the interference light generated by the interference of the first part of the light and the second part of the light increases. When the pressure of the hydraulic oil decreases, the measured hydraulic oil (5) flows out of the optical fiber defect through the sheath small hole (6) in the middle of the optical fiber defect sheath (3). The length L5 of the measured hydraulic oil (5) decreases, the length L4 of the first section of air (4) increases, and the length L7 of the second section of air (7) increases, but still satisfies L4 + L5 + L7 = L. The optical path of the second part of the light transmitted through the first section of air (4), the measured hydraulic oil (5), and the second section of air (7) decreases, and the phase of the second part of the light transmitted through the first section of air (4), the measured hydraulic oil (5), and the second section of air (7) also decreases accordingly. When the first part of the light meets the second part of the light, the phase difference obtained by subtracting the phase of the second part of the light from the phase of the first part of the light increases, and the intensity of the interference light generated by the interference of the first part of the light and the second part of the light decreases.

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