Online detection method and device for oil content, porosity and thickness of PE (Poly Ethylene) partition plate of lead-acid storage battery

Abstract

The invention discloses an online detection method and device for the oil content, porosity and thickness of a lead-acid storage battery PE partition plate. The online detection method comprises the following steps: establishing a physical model, analyzing internal pores and oil content of the PE partition plate based on propagation characteristics of terahertz pulse waves and a defect detection principle of reflected signals, and detecting the thickness of the PE partition plate by using terahertz. The device comprises a detector, a computer control system and a display, the detector is installed on an XY scanning platform, and the interior of the detector comprises a femtosecond laser, a beam splitter, a photoconductive antenna, an optical fiber delay line, a parabolic mirror, a semitransparent mirror and a data acquisition card. The femtosecond laser is used for emitting femtosecond laser pulses to generate THz pulse waves, and THz pulse reflected waves send signals acquired by the data acquisition card to the computer control system for data analysis and processing. According to the invention, non-contact, lossless and rapid detection of the PE partition plate can be realized, so that the production efficiency and quality stability of the PE partition plate are improved.

Description

Technical Field

[0001] The invention relates to the technical field of lead-acid battery PE separator production, in particular to an online detection method and device for oil content, porosity and thickness of a lead-acid battery PE separator. Background Art

[0002] At present, the production method of PE separators for lead-acid batteries is mainly based on the wet method, and the production line runs continuously. During the production process, the quality of PE separators is constantly monitored by the equipment, on-site sampling, and manual testing of the oil content, porosity, thickness, etc. of the separators in the laboratory with reference to relevant standards. The entire process is a "static" testing process. Once the laboratory finds that the oil content, porosity, thickness and other indicators of the tested separators do not meet the standards, the batches of products during the entire production period need to be re-inspected, and even worse, all batches of products during the period will be scrapped, which will seriously affect the production efficiency of the entire production line and the quality stability between batches of products.

[0003] Secondly, the online detection methods on the market still have certain defects during use. For example, the infrared thickness gauge is used online to detect the thickness of the PE separator. Since the working principle of the infrared thickness gauge is mainly based on the absorption, reflection and transmission characteristics of infrared light, when the infrared light is irradiated on the surface of the object, part of the light will be reflected or transmitted, and its intensity and phase will change with the change of the thickness of the object. The infrared thickness gauge calculates the thickness of the object by measuring these changes. When the infrared thickness gauge is used to detect the PE separator online, the vibration of the equipment and the displacement of the separator on the production line will easily cause a large error in the measurement of the thickness of the PE separator, causing a large number of false alarms and misjudgments in production; at the same time, since the separator has a certain width, in order to detect the thickness of each layer of the entire separator as much as possible, it is necessary to arrange multiple infrared thickness gauges in the horizontal direction of the production line, which causes chaos in the layout of the production line and is not conducive to improving production efficiency. As for the detection of the oil content and porosity of the separator, there is no relevant technology and equipment in the existing technology to realize online detection. All the oil content and porosity detection of PE separators are tested manually in the laboratory, which has the problems of low efficiency and large errors.

[0004] In addition, in the field of PE separator production, since the main characteristics of PE separators are determined by the microstructure and composition of the separators, the online detection device for product quality needs to be able to detect the microstructure and composition of the separators. For example, ① although the X-ray online detection device can detect the microstructure of the product, the X-ray online detection device occupies a large area and has high radiation, which has an adverse effect on the health of workers on the production line, and the X-ray online detection device cannot detect the composition of the PE separator; ② although the visual online detection device has a simple device layout and high stability, the visual online detection device can only detect the macroscopic quality problems of the separator, and cannot detect the microstructure and composition of the separator. However, there is a lack of records in the relevant field of the device that can be used online to detect the microstructure and composition of the PE separator. Summary of the invention

[0005] The purpose of the present invention is to provide an online detection method and device for the oil content, porosity and thickness of a PE separator of a lead-acid battery, which utilizes terahertz waves to realize non-contact, non-destructive and rapid detection of the PE separator, and directly presents the detection results in the form of images by converting the data, which can clearly and accurately reflect the thickness uniformity, porosity and pore distribution, and filling content and distribution of the PE separator, thereby improving the production efficiency and quality stability of the PE separator, so as to solve the shortcomings of the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The online detection method for oil content, porosity and thickness of PE separator of lead-acid battery comprises the following steps:

[0008] S1: Establish a physical model: define E0(ω) as the reference signal E obtained after the incident terahertz pulse wave propagates a distance L in the air ref (ω) is expressed as:

[0009] E ref (ω)=E0(ω)·p a (ω,L) (1)

[0010] Where ω is the frequency of the terahertz wave, p a (ω, L) is the propagation factor of terahertz waves in air medium, expressed as:

[0011]

[0012] In the formula, is the complex refractive index of air; c is the speed of light;

[0013] S2: Analyze the internal pores and oil content of the PE separator based on the propagation characteristics of terahertz pulse waves and the defect detection principle of reflected signals. The propagation distance of the interface reflected wave is twice the thickness of the medium.

[0014] S3: Using terahertz to detect the thickness of PE separator: According to formula (1), a reflection single-point thickness extraction model was established:

[0015]

[0016] When the terahertz wave is incident vertically, the single-point thickness extraction model is simplified to:

[0017]

[0018] Where, d is the thickness of the sample; T up and T do E up 、E do The flight time; n is the refractive index of the sample; c is the propagation speed of light in air;

[0019] By detecting the reference signal E transmitted through the air and the sample under test ref and the transmission signal E sam , a transmission single-point thickness extraction model was established:

[0020]

[0021] Wherein, the refractive indices of air and sample are n0 and n respectively; T sam and T ref E sam 、E sam of flight time.

[0022] Furthermore, according to the Fresnel formula in S1, when the terahertz pulse wave enters medium 2 from medium 1, refraction and reflection occur at the interface, and the refractive index t 12 and the reflection coefficient r 21 Respectively expressed as:

[0023]

[0024] In the formula, and are the complex refractive indices of medium 1 and medium 2, respectively, and the expressions are:

[0025]

[0026] Where n(w) is the real refractive index, which represents the dispersion characteristics of the medium, and κ(w) is the extinction characteristic, which represents the absorption characteristics of the medium. When the terahertz pulse wave E0(ω) is incident vertically from the air to a medium 1 with a thickness of d, the transmission signal Esam detected on the opposite side of the medium is expressed as:

[0027] E sam =E0(ω)·t a1 (ω)·p1(ω,d)·t 1a (ω) (6)

[0028] Terahertz pulse waves show weak absorption characteristics in insulating media, that is, κ1(ω)<<n1(ω).

[0029] Furthermore, the specific analysis method in S2 is as follows:

[0030] Set the incident wave to E0 and the reflected wave from the cardboard surface to E r0 , the reflected wave on the upper surface of the air gap is E r1 , the reflected wave from the lower surface of the air gap is E r2 , the reflected wave on the iron plate is E r3 ;

[0031] According to equations (3), (4) and (6), the reflected wave E on the paperboard surface is r0 The calculation formula is as follows:

[0032] E r0 =E0·r 1a (7)

[0033] Similarly, the reflected waves E on the upper and lower surfaces of the air gap r1 and E r2 They are expressed as:

[0034] E r1 =E0p1(ω,2d1)·t a1 r C1 t 1a (8)

[0035] E r2 =E0p1(ω,2d1)p C (ω,2d2)·t a1 t 1a t C1 t 1C r 1C (9)

[0036] From formulas (3), (4), (7), (8) and (9), we can get:

[0037]

[0038]

[0039] In the formula, p c (w, 2d2) is the propagation factor of terahertz wave in air medium; E r0 With E r1 、E r1 With E r2 Opposite polarity.

[0040] The present invention provides another technical solution: an online detection device for the oil content, porosity and thickness of a PE separator of a lead-acid battery, comprising a detector and a computer control system; the detector is installed on an XY scanning platform, the XY scanning platform is used to drive the detector to move in the X direction and the Y direction, and the XY scanning platform is located above the PE separator production line; the detector is provided with a light source output port and a detection probe, the light source output port and the detection probe are directly facing the PE separator on the production line; the detector is also electrically connected to the computer control system, and the computer control system is externally connected to a display.

[0041] Furthermore, the detector includes a femtosecond laser, a beam splitter, a photoconductive antenna, an optical fiber delay line, a parabolic mirror, a semi-transparent mirror and a data acquisition card; the femtosecond laser is used to emit femtosecond laser pulses, and the beam splitter is used to split the femtosecond laser pulses into two mutually perpendicular beams of light: a pumping light and a detection light; the pumping light generates a THz pulse wave through the optical fiber delay line and the photoconductive antenna, which is collimated and focused through the parabolic mirror, and the incident angle of the THz pulse wave is adjusted before being incident on the sample surface through the semi-transparent mirror, and the THz pulse reflected wave enters the detection probe in the same line as the detection light, and the detection probe sends the collected signal to the computer control system through the data acquisition card for data analysis and processing.

[0042] Furthermore, the detection probe is a THz pulse wave detector.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The method and device for online detection of oil content, porosity and thickness of PE separators for lead-acid batteries of the present invention can realize non-contact, non-destructive and rapid detection by using terahertz waves in the production process of PE separators for lead-acid batteries, convert the collected data through a computer control system, and directly present the detection results on a display in the form of images, which can clearly and accurately reflect the thickness uniformity, porosity and pore distribution, filling content and distribution of the PE separator, thereby improving the production efficiency and quality stability of the PE separator. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the framework structure of the detection device of the present invention;

[0046] Figure 2 This is a diagram of the internal optical path transmission of the detector of the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The online detection method for oil content, porosity and thickness of a lead-acid battery PE separator provided in an embodiment of the present invention comprises the following steps:

[0049] S1: Establish a physical model: define E0(ω) as the reference signal E obtained after the incident terahertz pulse wave propagates a distance L in the air ref (ω) is expressed as:

[0050] E ref (ω)=E0(ω)·p a (ω,L) (1)

[0051] Where ω is the frequency of the terahertz wave, p a (ω, L) is the propagation factor of terahertz waves in air medium, expressed as:

[0052]

[0053] In the formula, is the complex refractive index of air; c is the speed of light;

[0054] According to the Fresnel formula, when the terahertz pulse wave enters medium 2 from medium 1, refraction and reflection occur at the interface, and the refractive index t 12 and the reflection coefficient r 21 Respectively expressed as:

[0055]

[0056]

[0057] In the formula, and are the complex refractive indices of medium 1 and medium 2, respectively, and the expressions are:

[0058]

[0059] Where n(w) is the real refractive index, which represents the dispersion characteristics of the medium, and k(w) is the extinction characteristic, which represents the absorption characteristics of the medium. When the terahertz pulse wave E0(ω) is incident vertically from the air to a medium 1 with a thickness of d, the transmission signal Esam detected on the opposite side of the medium is expressed as:

[0060] E sam =E0(ω)·t a1 (ω)·p1(ω,d)·t 1a (ω) (6)

[0061] Terahertz pulse waves show weak absorption characteristics in insulating media, that is, κ1(ω)<<n1(ω).

[0062] S2: Based on the propagation characteristics of terahertz pulse waves and the defect detection principle of reflected signals, the internal pores and oil content of the PE separator are analyzed. The propagation distance of the interface reflected wave is twice the thickness of the medium. Specifically, the incident wave is set to E0 and the reflected wave on the paperboard surface is set to E r0 , the reflected wave on the upper surface of the air gap is E r1 , the reflected wave from the lower surface of the air gap is E r2 , the reflected wave on the iron plate is E r3 ;

[0063] According to equations (3), (4) and (6), the reflected wave E on the paperboard surface is r0 The calculation formula is as follows:

[0064] E r0 =E0·r 1a (7)

[0065] Similarly, the reflected waves E on the upper and lower surfaces of the air gap r1 and E r2 They are expressed as:

[0066] E r1 =E0p1(ω,2d1)·t a1 r C1 t 1a (8)

[0067] E r2 =E0p1(ω,2d1)p C (ω,2d2)·t a1 t 1a t C1 t 1C r 1C (9)

[0068] From formulas (3), (4), (7), (8) and (9), we can get:

[0069]

[0070]

[0071] In the formula, p c (w, 2d2) is the propagation factor of terahertz wave in air medium; E r0 With E r1 、E r1 With E r2 Opposite polarity.

[0072] S3: Use terahertz to detect the thickness of PE separator: According to formula (1), a reflective single-point thickness extraction model is established:

[0073]

[0074] When the terahertz wave is incident vertically, the single-point thickness extraction model is simplified to:

[0075]

[0076] Where, d is the thickness of the sample; T up and T do E up 、E do The flight time; n is the refractive index of the sample; c is the propagation speed of light in air;

[0077] Similarly, by detecting the reference signal E transmitted through the air and the sample under test ref and the transmission signal E sam , a transmission single-point thickness extraction model was established:

[0078]

[0079] Wherein, the refractive indices of air and sample are n0 and n respectively; T sam and T ref E sam 、E sam of flight time.

[0080] like Figure 1-2 As shown, in order to further and better explain the embodiments of the present invention, there is also provided an online detection device for the oil content, porosity and thickness of the PE separator of a lead-acid battery, including a detector and a computer control system; the detector is installed on an XY scanning platform, the XY scanning platform is used to drive the detector to move in the X direction and the Y direction, and the XY scanning platform is located above the PE separator production line; the detector is provided with a light source output port and a detection probe, the light source output port and the detection probe are facing the PE separator on the production line; the detector is also electrically connected to the computer control system, and the computer control system is externally connected to a display.

[0081] The detector includes a femtosecond laser, a beam splitter, a photoconductive antenna, an optical fiber delay line, a parabolic mirror, a half-mirror and a data acquisition card; the femtosecond laser is used to emit femtosecond laser pulses, and the beam splitter is used to split the femtosecond laser pulses into two mutually perpendicular beams of light: a pumping light and a detection light; the pumping light generates a THz pulse wave through the optical fiber delay line and the photoconductive antenna, which is collimated and focused through the parabolic mirror, and the incident angle of the THz pulse wave is adjusted before being incident on the sample surface through the half-mirror, and the THz pulse reflected wave enters the detection probe in the same line as the detection light, and the detection probe is a THz pulse wave detector, and the THz pulse wave detector sends the collected signal to the computer control system through the data acquisition card for data analysis and processing.

[0082] In the above embodiments, the present invention can realize non-contact non-destructive testing, wherein the terahertz detection device can perform detection without contacting the sample to be tested, avoiding the pollution, wear or damage that may be caused by contact in the traditional detection method. Secondly, the terahertz wave also has a shorter wavelength, which can provide high-precision measurement results and high-resolution imaging effects, so that the terahertz detection device can accurately identify the microstructure and subtle changes of the material of the PE separator. Thirdly, the terahertz wave can penetrate most common non-metallic materials, such as plastics, graphite, ceramics, etc. This feature makes terahertz detection have significant advantages in the detection of complex materials such as composite materials and multi-layer structures, and can detect the thickness and internal structure of multi-layer materials at one time. In addition, the photon energy of the terahertz wave is much lower than that of ionizing radiation such as X-rays, and the material to be detected will not be destroyed due to ionization, and it is safe and harmless to the human body. The present invention installs the detector on the XY scanning platform, has a faster detection speed, and can be applied to the online quality detection in the production process of PE separators, which helps to improve production efficiency and detection efficiency, and reduce detection costs and time costs.

[0083] In summary: the online detection method and device for the oil content, porosity and thickness of the PE separator of a lead-acid battery provided by the present invention can use terahertz waves (THz waves, with a frequency range of 0.1-10THz) for non-contact, non-destructive and rapid detection in the production process of the PE separator of the lead-acid battery. The terahertz waves have penetrating, coherent and fingerprint spectrum characteristics. The collected data is converted by a computer control system, and the detection results are directly presented on the display in the form of images, which can clearly and accurately reflect the thickness uniformity, porosity and pore distribution, filling content and distribution of the PE separator, thereby improving the production efficiency and quality stability of the PE separator.

[0084] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An online detection method for oil content, porosity and thickness of PE separators for lead-acid batteries, characterized in that: The following steps are involved: S1: Establish a physical model: define E0(ω) as the reference signal E obtained after the incident terahertz pulse wave propagates a distance L in the air ref (ω) is expressed as: E ref (ω)=E0(ω)·p a (ω,L)(1) Where ω is the frequency of the terahertz wave, p a (ω, L) is the propagation factor of terahertz waves in air medium, expressed as: In the formula, is the complex refractive index of air; c is the speed of light; S2: Analyze the internal pores and oil content of the PE separator based on the propagation characteristics of terahertz pulse waves and the defect detection principle of reflected signals. The propagation distance of the interface reflected wave is twice the thickness of the medium. S3: Using terahertz to detect the thickness of PE separator: According to formula (1), a reflection single-point thickness extraction model was established: When the terahertz wave is incident vertically, the single-point thickness extraction model is simplified to: Where, d is the thickness of the sample; T up and T do E up 、E do The flight time; n is the refractive index of the sample; c is the propagation speed of light in air; By detecting the reference signal E transmitted through the air and the sample under test ref and the transmission signal E sam , a transmission single-point thickness extraction model was established: Wherein, the refractive indices of air and sample are n0 and n respectively; T sam and T ref E sam 、E sam of flight time.

2. The online detection method for oil content, porosity and thickness of PE separator for lead-acid battery according to claim 1, characterized in that: According to the Fresnel formula in S1, when the terahertz pulse wave enters medium 2 from medium 1, refraction and reflection occur at the interface, and the refractive index t 12 and the reflection coefficient r 21 Respectively expressed as: In the formula, and are the complex refractive indices of medium 1 and medium 2, respectively, and the expressions are: Where n(w) is the real refractive index, which represents the dispersion characteristics of the medium, and k(w) is the extinction characteristic, which represents the absorption characteristics of the medium. When the terahertz pulse wave E0(ω) is incident vertically from the air to a medium 1 with a thickness of d, the transmission signal Esam detected on the opposite side of the medium is expressed as: E sam =E0(ω)·t a1 (ω)·p1(ω,d)·t 1a (oh)(6) Terahertz pulse waves show weak absorption characteristics in insulating media, that is, κ1(ω)<<n1(ω).

3. The online detection method for oil content, porosity and thickness of PE separator for lead-acid battery as claimed in claim 2, characterized in that: The specific analysis method in S2 is as follows: Set the incident wave to E0 and the reflected wave from the cardboard surface to E r0 , the reflected wave on the upper surface of the air gap is E r1 , the reflected wave from the lower surface of the air gap is E r2 , the reflected wave on the iron plate is E r3 ; According to equations (3), (4) and (6), the reflected wave E on the paperboard surface is r0 The calculation formula is as follows: E r0 =E0·r 1a (7) Similarly, the reflected waves E on the upper and lower surfaces of the air gap r1 and E r2 They are expressed as: E r1 =E0p1(ω,2d1)·t a1 r C1 t 1a (8) E r2 =E0p1(ω,2d1)p C (ω,2d2)·t a1 t 1a t C1 t 1C r 1C (9) From formulas (3), (4), (7), (8) and (9), we can get: In the formula, p c (w, 2d2) is the propagation factor of terahertz wave in air medium; E r0 With E r1 、E r1 With E r2 Opposite polarity.

4. An online detection device for oil content, porosity and thickness of PE separators of lead-acid batteries, characterized by: It comprises a detector and a computer control system; the detector is installed on an XY scanning platform, the XY scanning platform is used to drive the detector to move in the X direction and the Y direction, and the XY scanning platform is located above the PE partition production line; the detector is provided with a light source output port and a detection probe, and the light source output port and the detection probe are directly facing the PE partition on the production line; the detector is also electrically connected to the computer control system, and the computer control system is externally connected to a display.

5. The on-line detection device for oil content, porosity and thickness of PE separator for lead-acid battery as claimed in claim 4, characterized in that: The detector includes a femtosecond laser, a beam splitter, a photoconductive antenna, an optical fiber delay line, a parabolic mirror, a semi-mirror and a data acquisition card; the femtosecond laser is used to emit femtosecond laser pulses, and the beam splitter is used to split the femtosecond laser pulses into two mutually perpendicular beams of light: a pumping light and a detection light; the pumping light generates a THz pulse wave through the optical fiber delay line and the photoconductive antenna, which is collimated and focused through the parabolic mirror, and the incident angle of the THz pulse wave is adjusted before it is incident on the sample surface through the semi-mirror, and the THz pulse reflected wave enters the detection probe in the same line as the detection light, and the detection probe sends the collected signal to the computer control system through the data acquisition card for data analysis and processing.

6. The on-line detection device for oil content, porosity and thickness of PE separator for lead-acid battery as claimed in claim 5, characterized in that: The detection probe is a THz pulse wave detector.

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