Temperature monitoring device based on fiber bragg grating and battery device

Abstract

The utility model discloses a fiber bragg grating-based temperature monitoring device and a battery device, which relate to the technical field of optical fiber sensing and comprise a light source, a sensing fiber bragg grating unit, a demodulation unit and a temperature compensation device, and the temperature compensation device comprises a thermal expansion compensation device or a temperature adjusting device. The thermal expansion compensation device comprises at least one temperature compensation unit, each temperature compensation unit comprises a first thermal expansion device and two second thermal expansion devices, and the two ends of each demodulation fiber grating are fixedly connected with the two second thermal expansion devices of one temperature compensation unit. The two second thermal expansion devices of each temperature compensation unit are fixedly connected with the first thermal expansion device of each temperature compensation unit; each temperature compensation unit enables the central wavelength of each corresponding demodulation fiber grating to be unchanged when the external temperature changes through the deformation of the first thermal expansion device and the second thermal expansion device. The utility model further discloses a corresponding battery device. According to the utility model, the accuracy of temperature monitoring can be ensured, and the false alarm phenomenon can be prevented.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fiber sensing, in particular to a temperature monitoring device and a battery device based on fiber Bragg grating. Background Art

[0002] The emissions of traditional fuel vehicles are one of the main air pollution sources. Electric vehicles can improve air quality by reducing tailpipe emissions, contribute to curbing global climate change, and reduce dependence on oil resources. The battery is the power source of electric vehicles, directly affecting the vehicle's driving range and performance. A high energy density and reliable battery system are the keys to achieving long driving range and high performance. The battery cost accounts for a considerable portion of the total cost of electric vehicles. Therefore, the progress of battery technology and cost reduction are crucial for promoting the popularization of the electric vehicle market. The safety and durability of the battery system directly affect the reliability of electric vehicles and user trust. As an important development direction of future transportation, the success of electric vehicles depends to a large extent on the progress and maturity of battery technology.

[0003] Temperature, as a parameter for measuring the battery state, is an important monitoring object for battery safety. The industry usually uses a circuit module system for battery temperature monitoring, but there are still many problems: under extreme environmental conditions, the measurement accuracy of the circuit module system may decrease, resulting in inaccurate temperature measurement results. The optical fiber material of optical fiber sensors usually has high heat resistance and corrosion resistance, can work stably for a long time in a harsh environment, and the optical fiber also has characteristics such as pressure resistance, small volume, light weight, and anti-electromagnetic interference, which makes the optical fiber sensor have a longer service life and less maintenance requirements in industrial production.

[0004] At present, most of the fiber optic sensors for detecting temperature are based on Fiber Bragg Grating (FBG). For example, the segmented demodulation device based on fiber Bragg grating provided in Chinese Patent CN202121051736.3 includes a sensing fiber Bragg grating array, a circulator, a broadband light source, an isolator, and a demodulation unit. Its working mode is as follows: The light emitted by the broadband light source is input into the sensing fiber Bragg grating array through the circulator. When the external environmental temperature changes or the sensing fiber Bragg grating array generates strain due to vibration, the wavelength of the sensing fiber Bragg grating array will drift. The light reflected by the sensing fiber Bragg grating array enters the isolator through the 3rd port of the circulator, and the light output through the isolator enters the demodulation unit. When the wavelength of the light reflected by the sensing fiber Bragg grating array is within the corresponding wavelength band of the demodulation fiber Bragg grating, the corresponding demodulation unit will work, and the demodulation fiber Bragg grating will input the reflected light into the photodetector through the 3rd port of the circulator accordingly. The photodetector converts the received optical signal into an electrical signal, and the indicator light receives the electrical signal emitted by the photodetector and emits a bright light for alarm. However, the demodulation fiber Bragg grating in the segmented demodulation device based on fiber Bragg grating lacks a temperature compensation device. When the external environmental temperature changes, it will cause the reflection spectrum of the demodulation fiber Bragg grating to shift. When the temperature changes, the central wavelength of the reflected light drifts, resulting in the inability to guarantee the accuracy of temperature measurement and further leading to false alarms. Summary of the Invention

[0005] The purpose of the present utility model is to provide a temperature monitoring device and a battery device based on fiber Bragg grating to solve the problems existing in the above-mentioned prior art, which can ensure the accuracy of temperature monitoring and prevent the occurrence of false alarm phenomena.

[0006] To achieve the above purpose, the present utility model provides the following solutions:

[0007] The present utility model provides a temperature monitoring device based on fiber Bragg grating, including a light source, a sensing fiber Bragg grating unit, a demodulation unit, and a temperature compensation device, wherein:

[0008] The light beam emitted by the light source can be transmitted to the sensing fiber Bragg grating unit, and the sensing fiber Bragg grating unit can reflect the light beam;

[0009] There is at least one demodulation unit, and each demodulation unit includes a demodulation fiber Bragg grating. Each demodulation fiber Bragg grating is connected to the sensing fiber Bragg grating unit. The reflected light reflected by the sensing fiber Bragg grating unit can be input into each demodulation fiber Bragg grating, and the demodulation unit can perform temperature detection according to the reflected light reflected by the sensing fiber Bragg grating unit;

[0010] The temperature compensation device includes a thermal expansion compensation device or a temperature adjustment device. The thermal expansion compensation device includes at least one temperature compensation unit. Each temperature compensation unit includes a first thermal expansion device and two second thermal expansion devices. Both ends of each demodulation fiber grating are fixedly connected to the two second thermal expansion devices of one temperature compensation unit respectively. The two second thermal expansion devices of each temperature compensation unit are both fixedly connected to the first thermal expansion device of each temperature compensation unit. Each temperature compensation unit makes the center wavelength of the corresponding demodulation fiber grating unchanged when the external temperature changes through the deformation of the corresponding first thermal expansion device and the corresponding second thermal expansion device. One temperature adjustment device is arranged at each demodulation fiber grating, and the temperature adjustment device can keep the demodulation fiber grating at a set temperature.

[0011] Preferably, the expansion coefficients of the first thermal expansion device and the second thermal expansion device are different.

[0012] Preferably, one second thermal expansion device is fixedly connected to both ends on the same side of the first thermal expansion device of each temperature compensation unit. The ends of the two second thermal expansion devices of each temperature compensation unit that are far away from each other are fixedly connected to both ends of the same demodulation fiber grating respectively.

[0013] Preferably, a groove is arranged on one side of each first thermal expansion device. The two second thermal expansion devices of each temperature compensation device are arranged oppositely and at least partially extend into the corresponding grooves. The two second thermal expansion devices of each temperature compensation unit are respectively a first compensation part and a second compensation part. One end of the first compensation part of each temperature compensation unit that is far away from the second compensation part and one end of the second compensation part of each temperature compensation unit that is far away from the first compensation part are both fixedly connected to the inner side wall of the corresponding groove. A gap is left between the outer wall of each second thermal expansion device close to the inner bottom wall of the corresponding groove and the inner bottom wall of the corresponding groove.

[0014] Preferably, the connection points of each demodulation fiber grating and the two second thermal expansion devices of each temperature compensation unit are a first connection point and a second connection point. The part of the demodulation fiber grating between the first connection point and the second connection point is the working length of the demodulation fiber grating. The relationship among the thermal expansion coefficient of the first thermal expansion device, the thermal expansion coefficient of the second thermal expansion device, the working length of the demodulation fiber grating, the length of the first compensation part, the length of the second compensation part, and the length of the second thermal expansion device is:

[0015] A(L1 + L2) - BL3 = (G2 / G1) × L

[0016]

[0017] G2 = 2n eff Λ(α + ξ)

[0018] Wherein, A is the thermal expansion coefficient of the second thermal expansion device; L1 is the length of the first compensator; L2 is the length of the second compensator; B is the thermal expansion coefficient of the first thermal expansion device; L3 is the length of the first thermal expansion device; G2 / G1 is the proportionality coefficient; L is the working length of the demodulation fiber grating; n eff represents the effective refractive index of the fiber core, Λ represents the period of the demodulation fiber grating 301, P 11 and P 12 represent two components of the photoelastic tensor of the fiber material, ξ represents the thermo-optic coefficient of the fiber material, and α represents the thermal expansion coefficient of the fiber material.

[0019] Preferably, the bandwidths of the plurality of demodulation fiber gratings are all Δλ, the number of the demodulation fiber gratings is N, and the wavelength passing interval of the Nth demodulation fiber grating is (λ1 + Δλ×(N - 1), λ1 + Δλ×N), where N is an integer greater than 0.

[0020] Preferably, the sensing fiber grating unit can be coiled in a serpentine shape to form a coiled fiber grating. The coiled fiber grating includes a plurality of extending segments and a plurality of bending segments. The two ends of each bending segment are respectively connected to the end of one extending segment and the beginning of another extending segment, and at least one extending segment is provided between the two extending segments connected to each bending segment.

[0021] Preferably, the sensing fiber grating unit is an all-identical weak reflection fiber grating array. There are multiple demodulation units. Each demodulation unit further includes a photodetector and an alarm device. The photodetector of each demodulation unit is connected to the output port of the demodulation fiber grating of each demodulation unit, and the alarm device of each demodulation unit is connected to the photodetector of each demodulation unit.

[0022] The present invention provides a battery device, including the temperature monitoring device based on fiber grating and at least one battery body. The sensing fiber grating unit is arranged at each battery body, and each battery body is in contact with the corresponding sensing fiber grating unit.

[0023] The present invention has achieved the following technical effects compared with the prior art:

[0024] The present utility model provides a temperature monitoring device and a battery device based on fiber Bragg grating, including a temperature compensation device. The temperature compensation device includes a thermal expansion compensation device or a temperature adjustment device. The thermal expansion compensation device includes at least one temperature compensation unit. Each temperature compensation unit includes a first thermal expansion device and two second thermal expansion devices. Both ends of each demodulation fiber Bragg grating are fixedly connected to two second thermal expansion devices of a temperature compensation unit. The two second thermal expansion devices of each temperature compensation unit are both fixedly connected to the first thermal expansion device of each temperature compensation unit. Through the deformation of the first thermal expansion device and the second thermal expansion device, each corresponding demodulation fiber Bragg grating has a constant central wavelength when the external temperature changes. The present utility model compensates the demodulation fiber Bragg grating through the thermal expansion compensation device or the temperature adjustment device. One way is: the deformation generated by the first thermal expansion device and the second thermal expansion device with the change of temperature generates a force on the demodulation fiber Bragg grating, thereby adjusting the stress change received by the demodulation fiber Bragg grating, and further making the change amount of the central wavelength of the demodulation fiber Bragg grating 3 be 0. Another way is: the temperature of the demodulation fiber Bragg grating is adjusted through the temperature adjustment device, thereby preventing the central wavelength of the demodulation fiber Bragg grating from shifting due to temperature change. The present utility model can ensure the accuracy of temperature monitoring and prevent the occurrence of false alarm phenomena. Brief Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 Schematic structural diagram of the temperature monitoring device based on fiber Bragg grating provided in Embodiment 1;

[0027] Figure 2 Front view of the temperature compensation device provided in Embodiment 1;

[0028] Figure 3 Top view of the temperature compensation device provided in Embodiment 1;

[0029] Figure 4 Coiling schematic diagram of the sensing fiber Bragg grating unit provided in Embodiment 1;

[0030] Figure 5 Wrapping schematic diagram of the sensing fiber Bragg grating unit on the side of the battery body in Embodiment 4;

[0031] In the figure: 100, a fiber Bragg grating-based temperature monitoring device; 1, a light source; 2, a sensing fiber Bragg grating unit; 201, an extension section; 202, a bending section; 3, a demodulation unit; 301, a demodulation fiber Bragg grating; 302, a photodetector; 303, an alarm device; 4, a temperature compensation device; 401, a first thermal expansion device; 402, a second thermal expansion device; 403, a groove; 404, a first compensating member; 405, a second compensating member; 5, a gap; 6, a circulator; 7, a coupler. Detailed implementation manners

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. 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.

[0033] The purpose of the present invention is to provide a fiber Bragg grating-based temperature monitoring device and a battery device to solve the problems existing in the above-mentioned prior art, which can ensure the accuracy of temperature monitoring and prevent the occurrence of false alarms.

[0034] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific implementation manners.

[0035] Embodiment 1

[0036] As Figures 1-5As shown in the figure, this embodiment provides a temperature monitoring device 100 based on fiber Bragg grating, which includes a light source 1, a sensing fiber Bragg grating unit 2, a demodulation unit 3, and a temperature compensation device 4, where: The light beam emitted by the light source 1 can be transmitted into the sensing fiber Bragg grating unit 2, and the sensing fiber Bragg grating unit 2 can reflect the light beam; There is at least one demodulation unit 3, and each demodulation unit 3 includes a demodulation fiber Bragg grating 301. Each demodulation fiber Bragg grating 301 is connected to the sensing fiber Bragg grating unit 2. The reflected light reflected by the sensing fiber Bragg grating unit 2 can be input into each demodulation fiber Bragg grating 301, and the demodulation unit 3 can perform temperature detection according to the reflected light reflected by the sensing fiber Bragg grating unit 2; The temperature compensation device 4 includes a thermal expansion compensation device. The temperature compensation device 4 includes at least one temperature compensation unit. Each temperature compensation unit includes a first thermal expansion device 401 and two second thermal expansion devices 402. Both ends of each demodulation fiber Bragg grating 301 are fixedly connected to the two second thermal expansion devices 402 of a temperature compensation unit. The two second thermal expansion devices 402 of each temperature compensation unit are both fixedly connected to the first thermal expansion device 401 of each temperature compensation unit. Each temperature compensation unit makes the central wavelength of the corresponding demodulation fiber Bragg grating 301 unchanged when the external temperature changes through the deformation of the corresponding first thermal expansion device 401 and the corresponding second thermal expansion device 402.

[0037] It should be noted that at least one demodulation fiber Bragg grating 301 can be connected to the two second thermal expansion devices 402 of a thermal expansion compensation device. As a preferred embodiment, multiple demodulation fiber Bragg gratings 301 are provided on the two second thermal expansion devices 402 of a thermal expansion compensation device.

[0038] In this embodiment, the light source 1 emits a light beam and makes the light beam input into the sensing fiber Bragg grating unit 2; The sensing fiber Bragg grating unit 2 reflects the light beam and makes the reflected light input into each demodulation fiber Bragg grating 301; The temperature is detected by the demodulation unit 3. When the temperature changes, the first thermal expansion device 401 and the second thermal expansion device 402 deform with the temperature change, so as to pull the demodulation fiber Bragg grating 301. By adjusting the stress change received by the demodulation fiber Bragg grating 301, the change amount of the central wavelength of the demodulation fiber Bragg grating 301 is 0. The temperature compensation device 4 of this embodiment can make the central wavelength of the demodulation fiber Bragg grating 301 not affected by the change of the external environmental temperature, that is, make the central wavelength of the demodulation fiber Bragg grating 301 unchanged, so as to perform temperature compensation on the demodulation fiber Bragg grating 301, prevent the central wavelength of the reflected light of the demodulation fiber Bragg grating 301 from drifting when the external environmental temperature changes, ensure the accuracy of temperature monitoring, and prevent the occurrence of false alarm phenomena.

[0039] In this embodiment, the expansion coefficients of the first thermal expansion device 401 and the second thermal expansion device 402 are different.

[0040] In this embodiment, a second thermal expansion device 402 is fixedly connected to both ends of the first thermal expansion device 401 on the same side of each temperature compensation unit. The ends of the two second thermal expansion devices 402 of each temperature compensation unit, which are away from each other, are fixedly connected to both ends of the same demodulation fiber grating 301 respectively.

[0041] In this embodiment, a groove 403 is provided on one side of each first thermal expansion device 401. The two second thermal expansion devices 402 of each temperature compensation device 4 are arranged oppositely and at least partially extend into the corresponding grooves 403; the two second thermal expansion devices 402 of each temperature compensation unit are respectively a first compensation member 404 and a second compensation member 405. The end of the first compensation member 404 of each temperature compensation unit, which is away from the second compensation member 405, and the end of the second compensation member 405 of each temperature compensation unit, which is away from the first compensation member 404, are both fixedly connected to the inner side wall of the corresponding groove 403; a gap 5 is left between the outer wall of each second thermal expansion device 402 near the inner bottom wall of the corresponding groove 403 and the inner bottom wall of the corresponding groove 403. A gap 5 is left between the lower end of the second thermal expansion device 402 and the inner bottom wall of the groove 403 in this embodiment, that is, only one end of the second thermal expansion device 402 is fixedly connected to the first thermal expansion device 401, and the other end is a free end and points to the center of the groove 403, which can ensure that the second thermal expansion device 402 can deform freely and avoid contact between the outer bottom wall of the second thermal expansion device 402 and the inner bottom wall of the groove 403, thus affecting the deformation. The lower end of the second thermal expansion device 402 is arranged in the groove 403, which can reduce the occupied volume.

[0042] In this embodiment, the connection points of each demodulation fiber grating 301 and the two second thermal expansion devices 402 of each temperature compensation unit are the first connection point and the second connection point. The part of the demodulation fiber grating 301 between the first connection point and the second connection point is the working length of the demodulation fiber grating 301. The relationship between the thermal expansion coefficient of the first thermal expansion device 401, the thermal expansion coefficient of the second thermal expansion device 402, the working length of the demodulation fiber grating 301, the length of the first compensation member, the length of the second compensation member, and the length of the second thermal expansion device 402 is Formula 1:

[0043] A(L1 + L2) - BL3 = (G2 / G1) × L Formula 1

[0044] Wherein, A is the thermal expansion coefficient of the second thermal expansion device; L1 is the length of the first compensation member; L2 is the length of the second compensation member; B is the thermal expansion coefficient of the first thermal expansion device; L3 is the length of the first thermal expansion device; G2 / G1 is the proportionality coefficient; L is the working length of each demodulation fiber grating 301.

[0045] When the external environmental temperature changes, the demodulation fiber Bragg grating 301 will have a central wavelength drift. For example, when the external environmental temperature rises, the refractive index of the demodulation fiber Bragg grating 301 (such as a chirped fiber Bragg grating) itself will change, and the grating gap 5 of the demodulation fiber Bragg grating 301 will also become larger due to expansion, causing the transmitted light to shift towards the long-wavelength direction, thus causing errors. Among them, the formula for the central wavelength offset of the demodulation fiber Bragg grating 301 (Formula 2) is expressed as:

[0046]

[0047] Among them, λ B represents the central wavelength of the demodulation fiber Bragg grating 301, n eff represents the effective refractive index of the fiber core, Λ represents the period of the demodulation fiber Bragg grating 301, P 11 and P 12 represent two components of the photoelastic tensor of the fiber material, ξ represents the thermo-optic coefficient of the fiber material, Δε represents the strain change, ΔT represents the temperature change of the demodulation fiber Bragg grating 301, v represents the Poisson's ratio coefficient of the fiber material, and α represents the thermal expansion coefficient of the fiber material.

[0048] Formula 2 represents the relationship between the change in the central wavelength Δλ B of the demodulation fiber Bragg grating 301 and temperature T and strain ε. To ensure that the central wavelength of the demodulation fiber Bragg grating 301 does not change, it is necessary to make the change in the central wavelength of the demodulation fiber Bragg grating 301 zero. In this embodiment, the first thermal expansion device 401 and the second thermal expansion device 402 are strained by the influence of temperature, causing stress on the demodulation fiber Bragg grating 301. When the temperature rises, the demodulation fiber Bragg grating 301 is slightly squeezed under the action of the first thermal expansion device 401 and the second thermal expansion device 402, so there is the following Formula 3:

[0049] Δε = k{A(L1 + L2) + BL2 + CL} = ΔL / L Formula 3

[0050] Among them, k is the coefficient of the relationship between the length and strain of the demodulation fiber Bragg grating 301, and C is the thermal expansion coefficient of the demodulation fiber Bragg grating 301. The calculation is simplified through the following Formulas 4 and 5:

[0051]

[0052] G2 = 2 neff Λ(α + ξ) Formula 5

[0053] Among them, n eff in Formulas 4 and 5 is set to the effective refractive index of the fiber core at room temperature, and Λ is set to the period of the demodulation fiber Bragg grating 301 at room temperature.

[0054] Through the above formula 2-5, the relational expressions among the thermal expansion coefficient of the first thermal expansion device 401, the thermal expansion coefficient of the second thermal expansion device 402, the working length of the demodulation fiber Bragg grating 301, the length of the first compensator, the length of the second compensator, and the length of the second thermal expansion device 402 can be obtained. By selecting and setting the demodulation fiber Bragg grating 301, the first thermal expansion device 401, and the second thermal expansion device 402, the relationships of various parameters are made to satisfy formula 1, so as to ensure that the change amount of the central wavelength of the demodulation fiber Bragg grating 301 is 0. Thus, when the temperature changes, the wavelength passing interval remains unchanged. The first thermal expansion device 401 and the second thermal expansion device 402 can be made of materials with negative thermal expansion coefficients or positive thermal expansion coefficients.

[0055] In this embodiment, the sensing fiber Bragg grating unit 2 can be coiled in a serpentine shape to form a coiled fiber Bragg grating. The coiled fiber Bragg grating includes a plurality of extending segments 201 and a plurality of bending segments 202. The two ends of each bending segment 202 are respectively connected to the end of one extending segment 201 and the beginning of another extending segment 201. At least one extending segment 201 is provided between the two extending segments 201 connected to each bending segment 202. That is, the plurality of extending segments 201 are arranged in sequence in the same direction, and the two ends of each bending segment 202 are respectively connected to two spaced-apart extending segments 201. The sensing fiber Bragg grating unit 2 of this embodiment adopts a way of spaced-apart bending and coiling, as Figure 4 shown, preventing the occurrence of inaccurate measurement data and reduced service life of the optical fiber caused by excessive bending of the optical fiber.

[0056] In this embodiment, the sensing fiber Bragg grating unit 2 is an all-identical weak reflection fiber Bragg grating array, and the sensing fiber Bragg grating unit 2 is provided with a plurality of temperature sensing fiber Bragg grating units. The beam passing through each temperature sensing fiber Bragg grating unit will cause reflection. Since a weak reflection fiber Bragg grating is used as the temperature sensing component, the loss of light intensity can be reduced. The number of the plurality of temperature sensing fiber Bragg grating units can be set, allowing the detection of a plurality of temperature sensing fiber Bragg grating units to realize the temperature measurement of the component to be measured.

[0057] As a preferred implementation manner, the difference in the central wavelengths of the fiber Bragg gratings written in the all-identical weak reflection fiber Bragg grating array shall not exceed 0.1 nm.

[0058] In this embodiment, there are a plurality of demodulation units 3. Each demodulation unit 3 further includes a photodetector 302 and an alarm device 303. The photodetector 302 of each demodulation unit 3 is connected to the output port of the demodulation fiber Bragg grating 301 of each demodulation unit 3, and the alarm device 303 of each demodulation unit 3 is connected to the photodetector 302 of each demodulation unit 3.

[0059] In this embodiment, the bandwidths of the multiple demodulation fiber Bragg gratings are all Δλ, the number of the demodulation fiber Bragg gratings is N, and the wavelength passing range of the Nth demodulation fiber Bragg grating is (λ1 + Δλ×(N - 1), λ1 + Δλ×N), where N is an integer greater than 0. The wavelength ranges of the multiple demodulation fiber Bragg gratings 301 do not overlap to achieve the monitoring of multiple temperature ranges. As a preferred implementation manner, the number of demodulation units 3 is preferably 8. The bandwidths of the demodulation fiber Bragg gratings 301 are all Δλ. The wavelength passing range of the first demodulation fiber Bragg grating 301 is (λ1, λ1 + Δλ), and the temperature range it detects is 20 - 30 °C; the wavelength passing range of the second demodulation fiber Bragg grating 301 is (λ1 + Δλ, λ1 + 2Δλ), and the temperature range it detects is 30 - 40 °C; by analogy, the wavelength passing range of the eighth demodulation fiber Bragg grating 301 is (λ1 + 7Δλ, λ1 + 8Δλ), and the temperature range it detects is 110 - 120 °C. Temperature will change the grating of the weak reflection fiber Bragg grating. The reason is that the thermo-optic effect causes the refractive index of the fiber Bragg grating to change, and the thermal expansion coefficient causes the grating to change, thereby changing the reflected wavelength. When the temperature changes, the wavelength of the light reflected by the weak reflection fiber Bragg grating drifts. The reflected light passes through the circulator 6 and the coupler 7 in sequence and then reaches the demodulation fiber Bragg grating 301. Each demodulation fiber Bragg grating 301 has a corresponding passing wavelength range, allowing the light with a wavelength within the range to pass through and filtering out the light with a wavelength not within the range. After the reflected light passes through the corresponding demodulation fiber Bragg grating 301, it is converted into an electrical signal by the photoelectric converter to turn on the warning light. By observing different warning lights, the overall temperature condition of the component to be measured (such as the battery) can be obtained. When there is an abnormality in an individual battery cell and the temperature is not within the normal operating range, the reflected light of a certain wavelength will cause the warning light to turn on after the above steps, enabling the driver to know that there is a special situation with the battery temperature.

[0060] In this embodiment, the demodulation fiber Bragg grating 301 is preferably a chirped fiber Bragg grating, and the alarm device 303 is preferably a warning light.

[0061] In this embodiment, it further includes a circulator 6 and a beam splitter. The light source 1 is connected to port a of the circulator 6 through a transmission optical fiber. Port b of the circulator 6 is connected to the sensing fiber grating unit 2. Port c of the circulator 6 is connected to a 1×10 coupler 7 through a transmission optical fiber. The 10 output ports of the circulator 6 are respectively connected to 10 demodulation fiber gratings 301. The output ports of the 10 demodulation fiber gratings 301 are connected to 10 photodetectors 302. Each photodetector 302 is connected to an alarm device 303. The light beam emitted by the light source 1 enters the circulator 6 through the transmission optical fiber and is output from port c of the circulator 6 to the all-identical weak reflection fiber grating array. Each temperature sensing fiber grating unit in the all-identical weak reflection fiber grating array is an identical weak reflection fiber grating. The reflected light reflected by the all-identical weak reflection fiber grating array is transmitted to the coupler 7 through the circulator 6, and the reflected light is split into each demodulation fiber grating 301 through the coupler 7. The temperature compensation device 4 enables the demodulation fiber grating 301 not to be affected by the external environment, so that the wavelength passing intervals of the respective demodulation fiber gratings 301 are fixed. The demodulation fiber gratings 301 are connected to the photodetectors 302. When the temperature range satisfies the detection range of the demodulation fiber grating 301, the light of this wavelength is passed by the demodulation fiber grating 301, reflected by other chirped fiber gratings, and the passed light enters the corresponding photodetector 302. The photodetector 302 converts the optical signal into an electrical signal, and thus temperature warning is carried out through a warning lamp. The structure of this embodiment is simple, the connection method is convenient, only the most basic fusion splicing between optical fibers is required, expensive spectrometers and demodulation devices are not needed, the cost is low, the manufacturing method is simple, it is suitable for industrial production, and it meets the requirements of real-time monitoring of the battery temperature change and segmented display of the temperature change.

[0062] As a preferred implementation manner, the optical fibers in this embodiment are all single-mode optical fibers, with the model of G652, the core diameter of the optical fiber is 9μm, and the cladding diameter is 125μm.

[0063] Embodiment 2

[0064] This embodiment provides a temperature monitoring device 100 based on fiber Bragg grating, which includes a light source 1, a sensing fiber Bragg grating unit 2, a demodulation unit 3, and a temperature compensation device 4, where: the light beam emitted by the light source 1 can be transmitted into the sensing fiber Bragg grating unit 2, and the sensing fiber Bragg grating unit 2 can reflect the light beam; there is at least one demodulation unit 3, each demodulation unit 3 includes a demodulation fiber Bragg grating 301, each demodulation fiber Bragg grating 301 is connected to the sensing fiber Bragg grating unit 2, and the reflected light reflected by the sensing fiber Bragg grating unit 2 can be input into each demodulation fiber Bragg grating 301, and the demodulation unit 3 can perform temperature detection according to the reflected light reflected by the sensing fiber Bragg grating unit 2; the temperature compensation device 4 is a temperature adjustment device, and a temperature adjustment device is provided at each demodulation fiber Bragg grating 301, and the temperature adjustment device can keep the demodulation fiber Bragg grating 301 at a set temperature, such as 20 °C. As a preferred implementation manner, when the temperature monitoring device 100 based on fiber Bragg grating is applied to an automobile, the refrigeration system (such as a thermoelectric cooler) on the automobile can be used as the temperature compensation device 4.

[0065] It should be noted that one temperature adjustment device can adjust the temperature for at least one demodulation fiber Bragg grating 301. As a preferred implementation manner, a plurality of demodulation fiber Bragg gratings 301 are provided at one temperature adjustment device.

[0066] Embodiment 3

[0067] This embodiment provides a temperature monitoring method based on the temperature monitoring device 100 based on fiber Bragg grating in Embodiment 1, including the following steps:

[0068] Emitting a light beam through the light source 1 and inputting the light beam into the sensing fiber Bragg grating unit 2; reflecting the light beam through the sensing fiber Bragg grating unit 2 and inputting the reflected light into each demodulation fiber Bragg grating 301; performing temperature detection through the demodulation unit 3;

[0069] During the temperature detection process, the center wavelength of each demodulation fiber Bragg grating 301 is kept unchanged by a thermal expansion compensation device or a temperature adjustment device, where: each temperature compensation unit makes the center wavelength of the corresponding demodulation fiber Bragg grating 301 unchanged when the external temperature changes through the deformation of the corresponding first thermal expansion device 401 and the corresponding second thermal expansion device 402; the temperature adjustment device makes the center wavelength of each demodulation fiber Bragg grating 301 unchanged when the external temperature changes by keeping the temperature of each demodulation fiber Bragg grating 301 at a set temperature value, thereby improving the monitoring accuracy.

[0070] Embodiment 4

[0071] This embodiment provides a battery device, which includes the fiber Bragg grating-based temperature monitoring device 100 in Embodiment 1 and at least one battery cell body. A sensing fiber Bragg grating unit 2 is arranged at each battery cell body, and each battery cell body is in contact with the corresponding sensing fiber Bragg grating unit 2. In this embodiment, the sensing fiber Bragg grating unit 2 and the fiber Bragg grating are applied to the battery device, such as an electric vehicle battery, replacing the traditional circuit module. Because the optical fiber itself has characteristics such as high temperature resistance, corrosion resistance, pressure resistance, small volume, light weight, and electromagnetic interference resistance, the temperature monitoring device has better stability, longer service life, and lower cost; the optical fiber is a passive device and will not produce adverse reactions such as heat generation during use. Using the demodulation fiber Bragg grating 301 as the main structure for reflecting the temperature of the electric vehicle battery cell core is stable, reliable, and has a simple structure without the need for complex circuits. The temperature compensation device 4 ensures that the demodulation fiber Bragg grating 301 will not cause wavelength drift due to changes in the external environmental temperature, making the temperature monitoring more accurate and reducing or avoiding situations such as false alarms and inaccurate alarms caused by changes in the environmental temperature.

[0072] As a preferred implementation manner, each temperature sensing fiber Bragg grating unit of the sensing fiber Bragg grating unit 2 is placed at the positive and negative electrodes of the electric vehicle battery cell core in a way of spaced bending and coiling, ensuring that the temperature sensing fiber Bragg grating unit can be in close contact with the battery cell body, and the stress on each part of the sensing fiber Bragg grating unit 2 is within the bending stress requirement of the optical fiber; enabling the change in the cell core temperature to be better transmitted to the temperature sensing fiber Bragg grating unit, making the monitoring data more accurate, and this structure does not require the optical fiber to extend into the battery cell core and does not require complex drilling and encapsulation techniques.

[0073] As a more preferred implementation manner, the battery cell body includes multiple rows of battery cell cores. Each row of battery cell cores includes battery cell cores, and the positive and negative electrodes of the battery cell cores are both wound with the sensing fiber Bragg grating unit 2. The extension section extends along each row of battery cell cores, and each row of battery cell cores corresponds to an extension section. There are multiple temperature sensing fiber Bragg grating units on each extension section, and each battery cell core corresponds to one temperature sensing fiber Bragg grating unit. The sensing fiber Bragg grating unit 2 is arranged in the spaced winding manner as shown in Figure 5 at both the positive and negative electrodes of the battery cell body. After the sensing fiber Bragg grating unit 2 is wound at the positive or negative electrode of the battery cell body, as shown in Figure 5 it can extend from the side of the battery cell body to the negative or positive electrode of the battery cell body.

[0074] As a preferred implementation manner, the normal temperature range of an electric vehicle battery is 20 - 40 °C. The temperature range detected by a certain demodulation fiber Bragg grating 301 can be set to 50 - 60 °C for high-temperature alarm of the battery.

[0075] In this utility model, specific examples are used to elaborate on the principle and implementation manner of the utility model. The description of the above embodiments is only used to help understand the method and its core idea of the utility model; at the same time, for those of ordinary skill in the art, according to the idea of the utility model, there will be changes in the specific implementation manner and application scope. To sum up, the content of this specification should not be construed as a limitation to the utility model.

Claims

1. A temperature monitoring device based on fiber Bragg grating, characterized in that: It includes a light source, a sensing fiber grating unit, a demodulation unit, and a temperature compensation device, where: The light beam emitted by the light source can be transmitted into the sensing fiber grating unit, and the sensing fiber grating unit can reflect the light beam; There is at least one demodulation unit, and each demodulation unit includes a demodulation fiber grating. Each demodulation fiber grating is connected to the sensing fiber grating unit. The reflected light reflected by the sensing fiber grating unit can be input into each demodulation fiber grating, and the demodulation unit can perform temperature detection according to the reflected light reflected by the sensing fiber grating unit; The temperature compensation device includes a thermal expansion compensation device or a temperature adjustment device. The thermal expansion compensation device includes at least one temperature compensation unit. Each temperature compensation unit includes a first thermal expansion device and two second thermal expansion devices. Both ends of each demodulation fiber grating are fixedly connected to the two second thermal expansion devices of one temperature compensation unit respectively. The two second thermal expansion devices of each temperature compensation unit are both fixedly connected to the first thermal expansion device of each temperature compensation unit; Through the deformation of the corresponding first thermal expansion device and the corresponding second thermal expansion device of each temperature compensation unit, the center wavelength of the corresponding demodulation fiber grating remains unchanged when the external temperature changes; A temperature adjustment device is provided at each demodulation fiber grating, and the temperature adjustment device can keep the demodulation fiber grating at a set temperature.

2. The temperature monitoring device based on fiber Bragg grating according to claim 1, characterized in that: The expansion coefficients of the first thermal expansion device and the second thermal expansion device are different.

3. The temperature monitoring device based on fiber Bragg grating according to claim 1, wherein: Both ends on the same side of the first thermal expansion device of each temperature compensation unit are fixedly connected to a second thermal expansion device respectively. The ends of the two second thermal expansion devices of each temperature compensation unit that are far away from each other are fixedly connected to both ends of the same demodulation fiber grating respectively.

4. The temperature monitoring device based on fiber Bragg grating according to claim 1, characterized in that: A groove is provided on one side of each first thermal expansion device. The two second thermal expansion devices of each temperature compensation device are arranged oppositely and at least partially extend into the corresponding grooves; The two second thermal expansion devices of each temperature compensation unit are respectively a first compensation piece and a second compensation piece. One end of the first compensation piece of each temperature compensation unit that is far away from the second compensation piece and one end of the second compensation piece of each temperature compensation unit that is far away from the first compensation piece are both fixedly connected to the inner side wall of the corresponding groove; There is a gap between the outer wall of each second thermal expansion device close to the inner bottom wall of the corresponding groove and the inner bottom wall of the corresponding groove.

5. The temperature monitoring device based on fiber Bragg grating according to claim 4, wherein: The connection points of each demodulation fiber grating with the two second thermal expansion devices of each temperature compensation unit are the first connection point and the second connection point. The part of the demodulation fiber grating between the first connection point and the second connection point is the working length of the demodulation fiber grating. The relationship between the thermal expansion coefficient of the first thermal expansion device, the thermal expansion coefficient of the second thermal expansion device, the working length of the demodulation fiber grating, the length of the first compensation piece, the length of the second compensation piece, and the length of the second thermal expansion device is: A(L1 + L2) - BL3 = (G2 / G1)×L G2 = 2n eff Λ(α + ξ) Wherein, A is the thermal expansion coefficient of the second thermal expansion device; L1 is the length of the first compensator; L2 is the length of the second compensator; B is the thermal expansion coefficient of the first thermal expansion device; L3 is the length of the first thermal expansion device; G2 / G1 is the proportionality coefficient; L is the working length of the demodulation fiber grating; n eff represents the effective refractive index of the fiber core, Λ represents the period of the demodulation fiber grating 301, P 11 and P 12 represent two components of the elasto-optic tensor of the optical fiber material, ξ represents the thermo-optic coefficient of the optical fiber material, and α represents the thermal expansion coefficient of the optical fiber material.

6. The temperature monitoring device based on fiber Bragg grating according to claim 1, characterized in that: The bandwidths of the multiple demodulation fiber Bragg gratings are all Δλ, the number of the demodulation fiber Bragg gratings is N, and the wavelength passing range of the Nth demodulation fiber Bragg grating is (λ1 + Δλ×(N - 1), λ1 + Δλ×N), where N is an integer greater than 0.

7. The temperature monitoring device based on fiber Bragg grating according to any one of claims 1-6, characterized in that: The sensing fiber Bragg grating unit can be coiled in a serpentine shape to form a coiled fiber Bragg grating. The coiled fiber Bragg grating includes a plurality of extending segments and a plurality of bending segments. The two ends of each bending segment are respectively connected to the end of one extending segment and the beginning of another extending segment, and at least one extending segment is arranged between the two extending segments connected to each bending segment.

8. The temperature monitoring device based on fiber Bragg grating according to any one of claims 1-6, characterized in that: The sensing fiber Bragg grating unit is an all-identical weak reflection fiber Bragg grating array; there are multiple demodulation units. Each demodulation unit further includes a photodetector and an alarm device. The photodetector of each demodulation unit is connected to the output port of the demodulation fiber Bragg grating of each demodulation unit, and the alarm device of each demodulation unit is connected to the photodetector of each demodulation unit.

9. A battery device, characterized in that: It includes the fiber Bragg grating-based temperature monitoring device according to any one of claims 1 - 8 and at least one battery body. The sensing fiber Bragg grating unit is arranged at each battery body, and each battery body is in contact with the corresponding sensing fiber Bragg grating unit.

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