Detection sensor and monitoring

Abstract

The present invention reduces the burden of installing a detection sensor for monitoring a liquid such as a liquid resin. A detection sensor according to the present invention comprises: an optical transmission body group that includes a plurality of optical transmission bodies which each transmit light supplied from a light source; and a thin band-shaped holder that supports the optical transmission body group. The holder is provided with a first holder element that supports one or more optical transmission body groups, on a support surface that expands in a first direction and in a second direction orthogonal to the first direction. The plurality of optical transmission bodies are arranged in the second direction.

Description

Detection Sensors and Monitoring

[0001] The present disclosure relates to a sensor for detecting liquid substances, and more particularly to a liquid substance detection sensor that can grasp the state of impregnation during an impregnation operation in which a fiber substrate is impregnated with a liquid resin under vacuum.

[0002] Fiber-reinforced plastics (FRP), a lightweight yet high-strength material, uses glass and carbon fibers as reinforcing fibers. It is widely used as a composite material in aircraft wings, ships, wind turbine rotors, railway vehicles, and architectural structural components. One molding method for composite components involves impregnating a reinforcing fiber substrate placed in a mold with uncured liquid resin and then curing the resin after impregnation to produce a molded product of a desired shape. This molding method is called RTM (Resin Transfer Molding). Because FRP components, which use the aforementioned composite materials, require a certain level of strength, it is essential for RTM to thoroughly impregnate the reinforcing fiber substrate with resin to prevent unimpregnation defects that reduce strength. Therefore, in industrial RTM production of FRP components, detecting and monitoring the resin distribution throughout the reinforcing fiber is necessary to ensure the strength of the FRP components.

[0003] Patent Document 1 discloses a liquid detection sensor for monitoring resins that is easy to process and has little variation in light response characteristics. Patent Document 1 includes a first optical path that transmits light from a light source, a curved portion (light scattering portion) that scatters the light transmitted through the first optical path to the outside, and a second optical path that transmits the light that enters through the curved portion to a predetermined position. In the detection sensor of Patent Document 1, the first optical path, the curved portion, and the second optical path are made of a light-transmitting material, and the amount of light scattered to the outside at the curved portion is greater than the amount of light scattered to the outside at the first optical path or the amount of light scattered to the outside at the second optical path.

[0004] Japanese Patent Application Laid-Open No. 2007-218653

[0005] The present disclosure aims to reduce the burden of installing detection sensors for monitoring liquid materials such as liquid resin.

[0006] The detection sensor according to the present disclosure comprises: an optical transmission element group including a plurality of optical transmission elements each transmitting light supplied from a light source; and a thin ribbon-shaped holder supporting the optical transmission element group, wherein the holder comprises a first holder element (21) supporting one or more of the optical transmission element groups on a support surface extending in a first direction (longitudinal direction L) and a second direction (width direction W) perpendicular to the first direction, and the plurality of optical transmission elements are arranged in the second direction.

[0007] The monitoring system according to the present disclosure includes a resin impregnation unit (80) in which reinforcing fibers (RF) placed inside a mold are impregnated with a liquid resin, detection units (90A, 90B) that detect the impregnated resin in the resin impregnation unit (80), and a control unit (70) that controls a monitoring operation of the impregnated resin. The detection units (90A, 90B) include any one of the detection sensors (1) according to the present disclosure.

[0008] The present disclosure provides a method for monitoring an impregnated resin, which detects the impregnation of a reinforcing fiber (RF) placed inside a mold with a liquid resin, by installing any one of the detection sensors (1) according to the present disclosure inside the mold adjacent to the reinforcing fiber (RF).

[0009] According to the detection sensor of the present disclosure, the first holder element supports one or more groups of optical transmission bodies on a support surface that extends in a first direction and a second direction perpendicular to the first direction, so that multiple detection surfaces can be provided by installing the first holder element only once, thereby reducing the installation burden according to the present disclosure.

[0010] 16 is a plan view showing a liquid material detection sensor according to an embodiment. FIG. 17 is a cross-sectional view taken along line IIA-IIA in FIG. 1 and a cross-sectional view taken along line IIB-IIB in FIG. 1. FIG. 18 is a diagram showing a modified example of a detection sensor according to an embodiment of the present disclosure. FIG. 19 is a diagram showing another modified example of a detection sensor according to an embodiment of the present disclosure. FIG. 19 is a diagram showing the detection principle of a detection sensor for detecting resin as a liquid material according to an embodiment of the present disclosure. FIG. 19 is a graph showing the relationship between the refractive index of a detection target and Fresnel reflectance. FIG. 19 is a diagram showing another modified example of a detection sensor according to an embodiment of the present disclosure. FIG. 19 is a diagram showing an outline of an RTM process. FIG. 19 is a diagram showing resin impregnation using three types of detection sensors. FIG. 19 is a diagram showing resin impregnation using detection sensor 1A. FIG. 19 is a diagram showing resin impregnation using detection sensor 1F. FIG. 19 is a diagram explaining differences in resin impregnation due to differences in the shape of the peripheral edge of the detection sensor. FIG. 19 is a diagram showing an example of a monitoring system according to an embodiment. FIG. 19 is a diagram showing another example of a monitoring system according to an embodiment. FIG. 19 is a diagram showing an example of the structure of a mold (upper mold) in a monitoring system according to an embodiment. FIG. 19 is a diagram showing the relationship between the mold and film in FIG.

[0011] Hereinafter, an embodiment will be described with reference to the accompanying drawings. The description includes a detection sensor 1 (1A to 1F), and a system (60A, 60B) and method for monitoring the detection of liquid resin as a liquid substance using the detection sensor 1 during the RTM process. The following will explain each embodiment in order.

[0012] [Detection sensor 1A: see FIGS. 1 to 8] The detection sensor 1A includes a plurality of optical fibers 10 and a holder 20 that sandwiches and supports the plurality of optical fibers 10 from the front and back. In the detection sensor 1A, the plurality of optical fibers 10 are supported by the holder 20, so that the plurality of optical fibers 10 can be arranged in a single operation by simply laying the holder 20 in the required location. The optical fiber 10 is an example of an optical transmission body according to the present disclosure. In addition, in the detection sensor 1A, a longitudinal direction L, a width direction W, a thickness direction T, as well as a front (F) and a rear (R) are defined as shown in FIGS. 1 and 2.

[0013] [Optical Fiber 10: Figures 1 and 2] The optical fiber 10 has a three-layer structure including a core, an outer clad, and a coating covering the clad. The refractive index of the core is higher than that of the clad, allowing light to propagate only to the central core as much as possible through total internal reflection and refraction. As an example, Figure 1 shows eight optical fibers 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H supported by a holder 20 with spacing in the width direction W. When it is necessary to distinguish between the eight fibers, they will be referred to as optical fibers 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H. When it is not necessary to distinguish between them, they will be referred to as optical fibers 10. The multiple optical fibers 10 are arranged with spacing in the width direction W. This spacing allows detection of the resin according to the progress of the liquid resin impregnation.

[0014] The optical fibers 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H have different lengths supported by the holder 20. That is, the optical fiber 10A is the longest, followed by the optical fibers 10B, 10C, 10D, 10E, 10F, 10G, and 10H in the order of decreasing length. Except for this length, the optical fibers 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H have the same specifications and constitute a group of optical transmission bodies according to the present disclosure. Each of the optical fibers 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H is provided with a connector 25 for connecting to a monitoring system.

[0015] [Holder 20: Figures 1 and 2] The holder 20 includes a first holder element 21 that supports a plurality of optical fibers 10 from one side, and a plurality of second holder elements 23 that support a plurality of optical fibers 10 from the other side. The first holder element 21 is made of, for example, a resin sheet, has a thin ribbon shape, and extends in a longitudinal direction L (first direction) and a width direction W (second direction) perpendicular to the longitudinal direction L. One side of the first holder element 21 constitutes the support surface of the present disclosure. Note that, for the purpose of the present disclosure, only the first holder element 21 is necessary, and the second holder element 23 is a preferred element in the present disclosure.

[0016] Each of the multiple second holder elements 23 is formed, for example, from a resin adhesive tape. The first holder element 21 has a larger surface area than the second holder element 23 and supports most of the multiple optical fibers 10. The multiple second holder elements 23 are attached to the first holder element 21 together with the multiple optical fibers 10 at intervals in the longitudinal direction L. The second holder elements 23 are attached to the first holder element 21 at intervals, and the first holder element 21 is open to the outside between adjacent second holder elements 23. The end face of the optical fiber 10 is disposed in the open portion where the second holder element 23 is not attached. The end face of the optical fiber 10 exposed to the outside serves as a detection surface DF for the resin impregnated during the RTM process. This detection surface DF forms a cleavage plane, and the detection surfaces DF formed by the cleavage planes of the multiple optical fibers 10 are arranged at offset positions in the longitudinal direction L.

[0017] The second holder element 23 is not limited to the above example, and may be provided in one or more regions in the longitudinal direction L of the first holder element 21, and may be provided over a part of the region in the width direction W or over the entire region.

[0018] As described above, the detection sensor 1A has the detection surfaces DF of the optical fibers 10 arranged at multiple locations that are offset in the longitudinal direction L. Therefore, the progress of resin impregnation can be detected sequentially at multiple locations, for example, by detecting that the resin has impregnated up to the optical fiber 10A, then detecting that the resin has impregnated up to the optical fiber 10B, and further detecting that the resin has impregnated up to the optical fiber 10C. Note that, although an example has been shown here in which the detection surfaces DF are offset in the longitudinal direction L in the order in which they are arranged from one side to the other in the width direction W, the offset in position is not limited to this order.

[0019] Resin detection is possible once the liquid resin reaches the detection surface DF at the tip of each optical fiber 10, so portions other than the tip do not necessarily need to be exposed to the outside. Also, in FIG. 1, an example is shown in which a gap is provided between adjacent optical fibers 10 in the width direction W to clearly indicate their presence. However, as shown in IIB-IIB in FIG. 2, adjacent optical fibers 10 may be in contact with each other without a gap in the width direction W. If such a gap exists, it can be sealed. Furthermore, as described below, second holder elements 23 can be attached along the longitudinal direction L to both sides of the first holder element 21 in the width direction W. In this case, the detection surface DF of the optical fiber 10 is surrounded by the second holder elements 23.

[0020] According to the detection sensor 1A described above, a plurality of optical fibers 10 are supported by the first holder element 21 of the holder 20. Therefore, by laying the first holder element only once, a plurality of detection surfaces can be provided, and therefore, the detection sensor 1A can reduce the burden of laying the optical fibers.

[0021] [Detection sensor 1B: see Figure 3] The detection sensor 1A has been shown as an example in which a plurality (N) of detection surfaces DF are provided in the longitudinal direction L. This is called a one-dimensional array type sensor, but a two-dimensional array type detection sensor 1B is also provided in which a plurality (M) of detection surfaces DF are provided in the width direction W in addition to the plurality (N) of detection surfaces DF in the longitudinal direction L.

[0022] The detection sensor 1B includes three (M=3) one-dimensional array sensor units 11B, 12B, and 13B. The sensor units 11B, 12B, and 13B, each including N optical fibers 10, are spaced apart in the width direction W. Therefore, the detection sensor 1B is a two-dimensional array sensor with N x M detection points. Although the second holder element 23 and other components are omitted from FIG. 3 , the second holder element 23 can cover the first holder element 21 so that only the detection surface DF is exposed to the outside. The detection sensor 1B allows more detection surfaces DF to be installed in a single installation operation.

[0023] [Detection sensor 1C: Fig. 4] Detection sensor 1A and detection sensor 1B are examples in which the optical fiber 10 supported by the holder 20 extends straight in the longitudinal direction L, but the present disclosure is not limited to this and may include a portion in which the optical fiber 10 curves from the longitudinal direction L to the width direction W. This example is shown as detection sensor 1C.

[0024] The detection sensor 1C includes N optical fibers 10, a first portion 11 extending in the longitudinal direction L, and a second portion 13 extending in the width direction W, and the first portion 11 and the second portion 13 are connected by an arc-shaped third portion 15. The detection surfaces DF of the N optical fibers 10 of the detection sensor 1C are, for example, spaced apart in the longitudinal direction L and provided at the same position in the width direction W.

[0025] [Measurement Principle and Detection Sensitivity: See Figures 5 and 6] Next, the detection principle and detection sensitivity of liquid resin in the detection sensor 1 will be described. This detection is based on Fresnel reflection. When light is incident on an interface where materials with different refractive indices are in contact, a portion of the light is reflected, a phenomenon known as Fresnel reflection. The magnitude of the reflection depends on the difference in refractive indices and the angle of incidence, but the amount of Fresnel reflected light is considered to be almost normal incidence and can be calculated using the formula shown in Figure 5. In the case of the detection sensor 1, a difference in the amount of reflected light occurs before and after the resin Re reaches the detection surface DF, which is the end face of the optical fiber 10. In other words, as shown in the graph in Figure 5, the amount of reflected light is smaller after the resin Re reaches the detection surface DF than when air is in contact with the detection surface DF before the resin Re reaches it, resulting in a difference ΔR.

[0026] The relationship between the refractive index (n2) of material 2 in contact with the sensing surface DF of optical fiber 10 and Fresnel reflectance R is shown in Figure 6. When material 2 is air, the Fresnel reflectance is -14.6 dB, and when material 2 is a specific resin, the Fresnel reflectance is -31.4 dB; it was confirmed that the difference in R between air and resin, ΔR, is -16.8 dB. The larger ΔR, the better the detection sensitivity for material 2, so it is preferable that the core of optical fiber 10 has a refractive index similar to that of the resin Re to be detected.

[0027] [Detection sensors 1D, 5: Figures 7 and 8] Next, detection sensors 1D and 1E will be described. Detection sensors 1D and 1E use a thin ribbon-shaped optical waveguide structure. This optical waveguide structure is a structure in which a material with a high refractive index is sandwiched between materials with a lower refractive index, providing a light path through which light propagates by total reflection. An optical waveguide is one form of optical transmission medium, but a thin ribbon-shaped or plate-shaped structure is often referred to as an optical waveguide structure.

[0028] The detection sensor 1D, which is made of an optical waveguide, includes multiple cores 41 with a relatively high refractive index and a clad 43 with a relatively low refractive index surrounding the cores 41. The multiple cores 41 are spaced apart in the width direction W and extend in the longitudinal direction L. As is known to those skilled in the art, the wiring pitch between the cores 41 in an optical waveguide can be set to 60 μm or less, particularly about 10 μm, allowing for a thinner sensor structure with higher-density optical wiring compared to the detection sensors 1A to 1C that use optical fiber 10. Although the illustrated detection sensor 1D is flat, the material constituting the cores 41 and clad 43 is flexible, so it easily bends when a load is applied.

[0029] The detection sensor 1D includes a resin introduction path 45 that allows the resin Re to be introduced into each of the cores 41 and reach the detection surface DF, which is the end face of the core 41. The resin introduction path 45 is a gap that penetrates from one of the front and rear surfaces (front surfaces) of the detection sensor 1D through the cladding 43 and the cores 41 in that order. The resin introduction path 45 is provided for each of the cores 41, and is positioned at a different position in the longitudinal direction L. The resin introduction path 45 has a rectangular opening in plan view and is parallel to the thickness direction T, i.e., perpendicular to the detection surface DF of the core 41. When the impregnated resin reaches the location where the detection sensor 1D is disposed, the resin Re penetrates the resin introduction path 45 and comes into contact with the core 41. Then, the probe light PL is reflected at the interface between the detection surface DF of the core 41 and the resin Re, and the impregnation of the resin Re can be detected by detecting this reflected light RL.

[0030] The detection sensor 1D shown in Fig. 7 is a one-dimensional array type sensor, but it can also be a two-dimensional array type sensor like the detection sensor 1B. Also, in the detection sensor 1D shown in Fig. 7, the core 41 is straight in the longitudinal direction L, but it can also have a curved portion like the detection sensor 1C. The same is true for the detection sensor 1E shown in Fig. 8.

[0031] The detection sensor 1E shown in FIG. 8 has the same basic configuration as the detection sensor 1D, but the detection surface DF is inclined in the thickness direction T. As an example, this inclined detection surface DF is provided with a reflection chamber 47, which is a triangular gap in side view that penetrates from the cladding 43 on one side to the cladding 43 on the other side in the thickness direction T. The probe light PL traveling through the core 41 from the rear (R) to the front (F) turns 90 degrees at the boundary between the detection surface DF and the reflection chamber 47 and continues on. If the resin Re reaches directly above the reflection chamber 47, the probe light PL that has turned and is traveling is reflected by the resin Re, travels in the opposite direction, turns 90 degrees at the boundary between the detection surface DF and the reflection chamber 47, and is reflected backward (R). The reflection chamber 47 is shielded from the outside by a shielding plate 49.

[0032] According to the detection sensors 1D and 1E, by providing an optical waveguide structure in a film or sheet and incorporating multiple detection surfaces DF, it is possible to implement multiple detection surfaces DF with a single sheet installation operation. In addition, the dimension in the thickness direction T can be made smaller than that of the detection sensors 1A to 1C. This reduces the impact of the surface shape of the detection sensor being transferred to the reinforcing fiber. Here, in the RTM process, the detection sensor is attached to the surface of the reinforcing fiber and heat-molded using a mold, after which the resin-impregnated member is removed from the mold. The shape of the detection sensor is then transferred to the surface of the reinforcing fiber as irregularities. To ensure that the transferred irregularities do not exceed the quality tolerance, the detection sensor must be as thin as possible, and the detection sensors 1D and 1E are well suited to meeting this requirement.

[0033] [Method for detecting impregnated resin: see Figures 9 and 10] Next, a method for detecting resin impregnation while regulating the resin flow path will be described. This method serves as a countermeasure against false detection of resin impregnation due to racetracking that can occur in the RTM process. Here, racetracking occurs as a result of small gaps that inevitably occur in the RTM process. In this embodiment, these gaps occur around the detection sensor 1, and the liquid resin Re preferentially flows through these gaps, which can cause racetracking.

[0034] [Outline of the RTM Process] First, an outline of the detection method for the RTM process will be described with reference to Fig. 9. The reinforcing fiber RF is housed between a pair of upper and lower dies 51 and 53. The detection sensor 1 is sandwiched, for example, between the reinforcing fiber RF and the upper die 51. Note that in Fig. 9, both ends of the upper die 51 and the lower die 53 in the X direction are open, but in an actual RTM process, the upper die 51 and the lower die 53 also cover both ends. The upper die 51 and the lower die 53, including this portion, are collectively referred to as a die 50.

[0035] A resin tank 55 that stores liquid resin Re to be impregnated into the interior of the mold 50 and a pump 57 that depressurizes and suctions the interior of the mold 50 are attached to the mold 50. When impregnating the reinforcing fiber RF with resin Re, the pump 57 is driven to depressurize the interior of the mold 50, thereby suctioning the resin Re in the resin tank 55 into the interior of the mold 50. The suctioned resin Re permeates the interior of the mold 50 from the lower left to the upper right in the figure. Note that, in the mold 50, the X direction, Y direction, and Z direction are defined as shown in FIG. 9 and other figures. Also, in FIG. 9, the gray portion of the reinforcing fiber RF indicates that it is impregnated with resin Re.

[0036] [Comparative Detection Sensors] Now, three types of detection sensors are prepared, as shown in FIG. 10 . The three types are, from the left in the figure, detection sensor 1, detection sensor 1A, and detection sensor 1F. Detection sensor 1 does not have a second holder element 23, and the periphery of the detection surface DF at the tip of the optical fiber 10 is open, forming a flow path for the resin Re that reaches it in all directions: the X, Y, and Z directions. Therefore, detection sensor 1 is denoted as XYZ-FP. Note that even detection sensor 1 that does not have a second holder element 23 can achieve the basic effect of the present disclosure, that is, multiple detection surfaces DF can be provided with a single installation operation. Detection sensor 1A has multiple second holder elements 23 intermittently arranged in the longitudinal direction L, so no flow path for the resin Re is formed in the Y direction, and only flow paths are formed in the X and Z directions. Therefore, detection sensor 1A is denoted as XZ-FP. The detection sensor 1F has multiple second holder elements 23 intermittently arranged in the longitudinal direction L, and also has second holder elements 23 on both sides in the width direction W. Therefore, each detection surface DF of the optical fiber 10 is located in a rectangular area surrounded by the rectangular second holder elements 23. When the resin Re reaches this rectangular area, its flow paths in the X and Y directions to other rectangular areas are restricted, and the resin Re flows through the Z-direction flow path in that area. Therefore, the detection sensor 1F is denoted as Z-FP.

[0037] [Flow of Resin Re] <Detection Sensor 1> Assume that liquid resin Re is impregnated into detection sensor 1 as shown in Figure 10. Even if the resin Re only directly reaches two optical fibers 10C and 10D, the resin Re that reaches optical fibers 10C and 10D may travel around optical fibers 10C and 10D in the Y direction and reach other optical fibers 10A, 10B, 10E, 10F, etc. Therefore, there is a risk of erroneous detection of resin Re at the locations marked with an x ​​in Figure 10. The locations marked with a circle in Figure 10 indicate that resin Re is properly detected.

[0038] <Detection sensor 1A> Assume that detection sensor 1A is impregnated with resin Re up to the same point as detection sensor 1. In detection sensor 1A, second holder elements 23 are provided intermittently in the longitudinal direction L, so that the flow path of resin Re from a strip-shaped region partitioned by adjacent second holder elements 23 to an adjacent strip-shaped region is restricted. Therefore, detection sensor 1A can selectively detect resin Re in the flow path of resin Re in the X direction and the Z direction. Note that in Figure 10, areas marked with a triangle indicate that resin Re may be erroneously detected.

[0039] <Detection sensor 1F> The detection sensor 1F is also impregnated with the resin Re up to the same extent as the detection sensor 1. In the detection sensor 1F, the detection surfaces DF of the optical fibers 10 are arranged in a rectangular region surrounded by the rectangular second holder elements 23. Therefore, the detection sensor 1F can selectively detect the resin Re in the flow path of the resin Re in the Z direction.

[0040] Let us further consider the detection sensor 1A with reference to FIG. 11 . If the detection sensor 1A were not placed, there would be a small gap G (see FIG. 13 ) at the end of the width direction W of the detection sensor 1A before the resin has reached the position of the detection sensor 1A, and the resin Re could potentially reach the detection surface DF as shown in FIG. 11 through this gap. In this case, with the detection sensor 1A, there is no element in the X direction that would hinder the flow of the resin Re, so the resin would easily reach the detection surface DF. As shown in FIG. 11 , a thin ribbon-shaped detection sensor 1A or the like may be covered on both sides with one or more sheets Se made of resin or other material for detection.

[0041] 12, in the case of the detection sensor 1F, even if the resin Re reaches through the gap at the end in the width direction W, the resin cannot reach the optical fiber 10 unless it first flows in the Z direction due to the presence of the second holder element 23. In other words, the second holder element 23 provided at the end in the width direction W can delay the arrival of the resin. If the resin Re reaches via the original route during the delay period of the resin Re, correct detection can be achieved without causing erroneous detection.

[0042] <End Face Structure of Detection Sensor: See FIG. 13> As shown in the upper part of FIG. 13, there is a risk of resin Re seeping in through a gap G between the detection sensor 1F and the sheets Se, Se covering the detection sensor 1F from the front and back at the end of the detection sensor in the width direction W. Therefore, it is preferable to adopt a shape of the second holder element 23 that fills this gap G. As shown in FIG. 13, the gap G has a tapered shape. Therefore, following the shape of this gap G, the second holder element 23 is tapered toward both ends in the width direction W. The tapered shape can be a tapered shape (lower left side of FIG. 13) or a monotonically inclined shape in the thickness direction T (lower right side of FIG. 13).

[0043] [Impregnation monitoring system: FIGS. 14 and 15] Next, a system for monitoring resin impregnation using the detection sensor 1 according to this embodiment will be described. Two examples, monitoring system 60A and monitoring system 60B, will be described here. Monitoring system 60A uses an optical switch that can transmit and receive probe light PL and signal light SL between multiple optical fibers 10 and switch the optical paths. Below, monitoring system 60A and monitoring system 60B will be described in that order.

[0044] [Monitoring System 60A] The monitoring system 60A includes a control unit 70 that controls the operation of monitoring the resin impregnation, a resin impregnation unit 80 where the RTM process is performed, and a detection unit 90A that detects the resin impregnation in the resin impregnation unit 80 and sends the detection result to the control unit 70.

[0045] The control unit 70 includes a light source 71 that emits probe light PL, a photodetector 73 that receives signal light SL, and an optical branching circuit 75 that sends the probe light PL from the light source 71 toward the detection unit 90A and receives signal light SL from the detection unit 90A and sends it toward the photodetector 73. The control unit 70 includes a signal processing / controller 77 that is connected to both the light source 71 and the photodetector 73 and emits the probe light PL to the light source 71 and receives the signal light SL received by the photodetector 73 to determine impregnation with the resin Re. The control unit 70 also includes a calculation / display unit 79 that acquires the probe light PL and the signal light SL from the signal processing / controller 77, calculates a reflectance difference ΔR before and after the light reaches the resin, and displays the reflectance difference ΔR and the determination result of resin impregnation.

[0046] The resin impregnation section 80 is equipped with the aforementioned mold 50, resin tank 55, and pump 57, and by driving the pump 57 while the reinforcing fiber RF to be impregnated with the resin Re is supported inside the mold 50, the resin Re is impregnated into the reinforcing fiber RF inside the mold 50.

[0047] The detection unit 90A includes a detection sensor 1 disposed inside the mold 50, and an optical switch 91 that sends probe light PL to the detection sensor 1 and receives signal light SL from the detection sensor 1. The optical switch 91 continuously switches the connection between the optical branching circuit 75 and any of the multiple optical fibers 10 of the detection sensor 1. For example, the optical switch 91 sequentially switches the connection between the optical branching circuit 75 and optical fiber 10A, the connection between the optical branching circuit 75 and optical fiber 10B, the connection between the optical branching circuit 75 and optical fiber 10C, and the connection between the optical branching circuit 75 and optical fiber 10D. This allows the signal processing / controller 77 to continuously obtain the detection results of the resin Re from each of the optical fibers 10A, 10B, 10C, and 10D.

[0048] 14, the resin Re is detected by the optical fibers 10C and 10D, but the resin Re has not yet reached the optical fibers 10A and 10B and cannot be detected. Correspondingly, the intensity of the signal light SL from the optical fibers 10A and 10B remains the same as before, but the intensity of the signal light SL from the optical fibers 10C and 10D decreases. In this way, the monitoring system 60A can detect the degree of impregnation with the resin Re.

[0049] [Monitoring system 60B: FIG. 15] The monitoring system 60B has the same configuration as the monitoring system 60A, except that the detection unit 90A of the monitoring system 60A is replaced with a detection unit 90B. The detection unit 90B includes an optical splitter / combiner 93 for processing the probe light PL and the signal light SL using multiplexing, which transmits multiple signals together over a single transmission path, and a detection sensor 1. The detection sensor 1 is the same as that of the detection unit 90A. The optical splitter / combiner 93 combines multiple branch lines 94 connected to each of the N optical fibers 10 into a single aggregate line 95, which is connected to the optical branching circuit 75 of the control unit 70.

[0050] When the transmission path is an optical fiber, wavelength division multiplexing (WDM) is mainly used for multiplexing, so it is preferable to use an optical splitter / combiner 93 that implements WDM. WDM refers to a method in which light of multiple wavelengths is transmitted inside a single optical transmission path (optical fiber). In addition to WDM, other multiplexing techniques such as frequency division multiplexing (FDM) and time division multiplexing (TDM) may also be used.

[0051] [Effects of the Monitoring Systems 60A and 60B] Using the detection sensor 1 according to this embodiment, the behavior of changes in the resin impregnation distribution over time can be grasped during the RTM process by automatically switching between the optical fibers 10 (60A) that constitute each sensor element, or by simultaneously detecting multiple optical fibers 10 (60B). This allows the impregnation conditions for the molded component in the RTM process to be optimally adjusted in-process. Therefore, the monitoring systems 60A and 60B not only ensure the quality of the molded component by reducing the risk of unimpregnated areas, but also improve efficiency by shortening the impregnation process time.

[0052] [Structure of Mold: See FIGS. 16 and 17] Next, a preferred structure of a mold 50 used in the RTM process will be described with reference to FIGS. 16 and 17. A sensor accommodating chamber 52 in which the detection sensor 1 is disposed is provided in an upper mold 51 of the mold 50. The sensor accommodating chamber 52 is recessed upward from the surface of the upper mold 51 facing the lower mold 53. A dimension T52 of the recess in the sensor accommodating chamber 52 is formed to be approximately the same as or slightly smaller than the thickness T1 of the detection sensor 1. Furthermore, the dimension X52 of the sensor accommodating chamber 52 from the side surface of the detection sensor 1 is preferably 10 mm or less.

[0053] One or more resin sheets Se are interposed between the detection sensors 1 and the upper mold 51. As shown in FIG. 17 , the detection sensors 1 are fixed to the sheets Se in advance, and then housed in the sensor housing chamber 52 together with a portion of the sheets Se. The detection sensors 1 can be fixed to the sheets Se by bonding, fusion, adhesive tape, or other methods. To identify the positions at which the detection sensors 1 are to be fixed, a template is prepared in advance, and the detection sensors 1 are fixed to predetermined positions on the sheets Se according to the template. FIG. 17 shows an example in which three (M=3) detection sensors 1 are fixed to the sheets Se. To position the sheets Se to which the detection sensors 1 are fixed at predetermined positions on the upper mold 51, it is preferable to display marks 56 and 58 at corresponding positions on the upper mold 51 and the sheets Se. The sheets Se are aligned with the upper mold 51 using the marks 56 and 58 as targets.

[0054] By providing the sensor accommodating chamber 52, the amount by which the detection sensor 1 protrudes from the upper mold 51 toward the reinforcing fiber RF below can be reduced, thereby reducing the extent to which the shape of the detection sensor 1 is transferred to the molded part. Furthermore, by making the depth of the sensor accommodating chamber 52 shallower within an acceptable range for FRP depression and wrinkles that occur near the transfer portion, the processing cost of the upper mold 51 can be reduced. By aligning the sheet Se with the upper mold 51 using the marks 56 as a guide, the detection sensor 1 can be easily accommodated in the sensor accommodating chamber 52. By making the width direction W of the sensor accommodating chamber 52 larger than the width direction W of the detection sensor 1, the work of accommodating the detection sensor 1 in the sensor accommodating chamber 52 can be simplified.

[0055] [Notes] The present disclosure can be understood as follows: [Note 1] A liquid detection sensor (1) comprising: an optical transmission element group (10) including a plurality of optical transmission elements (10) each transmitting light supplied from a light source; and a thin ribbon-shaped holder (20) supporting the optical transmission element group, wherein the holder (20) comprises a first holder element (21) supporting one or more optical transmission element groups (10) on a support surface extending in a first direction (longitudinal direction L) and a second direction (width direction W) perpendicular to the first direction, and the plurality of optical transmission elements (10) are arranged in the second direction.

[0056] [Supplementary Note 2] In Supplementary Note 1, preferably, the plurality of optical transmission bodies (10) are arranged at intervals in the second direction.

[0057] [Supplementary Note 3] In Supplementary Note 1 or Supplementary Note 2, preferably, each of the plurality of optical transmission bodies (10) has a liquid detection surface (DF), and the detection surfaces (DF) of the plurality of optical transmission bodies (10) are offset in position in the first direction.

[0058] [Supplementary Note 4] In any of Supplementary Note 1 to Supplementary Note 3, preferably, the detection surfaces (DF) of the plurality of optical transmitters (10) are shifted in position in the first direction in the order in which they are arranged in the second direction.

[0059] [Supplementary Note 5] In any of Supplementary Note 1 to Supplementary Note 4, preferably, each of the plurality of optical transmission bodies (10) extends straight in the first direction or includes a portion curved from the first direction to the second direction.

[0060] [Supplementary Note 6] In any of Supplementary Notes 1 to 4, preferably, the holder (20) includes a second holder element (23) that fixes the optical transmission body (10) to the first holder element 21.

[0061] [Supplementary Note 7] In Supplementary Note 6, preferably, the second holder element (23) is provided in one or more regions of the first holder element (21) in the first direction, and over a part of or all of the region in the second direction.

[0062] [Supplementary Note 8] In Supplementary Note 6 or Supplementary Note 7, preferably, the second holder element (23) is provided along the first direction on both ends of the first holder element (21) in the second direction.

[0063] [Appendix 9] An impregnated resin monitoring system (60A, 60B) comprising: a resin impregnation unit (80) in which reinforcing fibers (RF) placed inside a mold are impregnated with liquid resin; a detection unit (90A, 90B) that detects the impregnated resin in the resin impregnation unit (80); and a control unit (70) that controls a monitoring operation of the impregnated resin, wherein the detection unit (90A, 90B) is equipped with any of the detection sensors (1) of [Appendix 1] to [Appendix 8].

[0064] [Appendix 10] A method for monitoring an impregnated resin, which detects the impregnation of reinforcing fibers (RF) placed inside a mold with a liquid resin, comprising: installing a detection sensor (1) according to any one of [Appendix 1] to [Appendix 8] inside the mold and adjacent to the reinforcing fibers (RF).

[0065] In addition to the above, the configurations described in the above embodiments can be selected or changed as appropriate. For example, the optical fiber 10 is supported by the first holder element 21 by providing the second holder element 23, but the optical fiber 10 can also be supported by the first holder element 21 by, for example, bonding the optical fiber 10 to the first holder element 21. In other words, the embodiment of supporting the optical fiber 10 on the first holder element 21 is arbitrary.

[0066] 1, 1A, 1B, 1C, 1D, 1E, 1F Detection sensor 2 Material 11B, 12B, 13B Sensor unit 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H Optical fiber 11 First part 13 Second part 15 Third part 20 Holder 21 First holder element 23 Second holder element 41 Core 43 Cladding 45 Resin introduction path 47 Reflection chamber 49 Shielding plate 50 Mold 51 Upper mold 52 Sensor accommodating chamber 53 Lower mold 55 Resin tank 56 Mark 57 Pump 60A, 60B Monitoring system 70 Control unit 71 Light source 73 Photodetector 75 Optical branching circuit 77 Controller 79 Display unit 80 Resin impregnation unit 90A, 90B Detecting section 91 Optical switch 93 Optical distributor / combiner 94 Branching line 95 Collecting line DF Detection surface L Longitudinal direction RF Reinforced fiber PL Probe light RL Reflected light Re Resin SL Signal light T Thickness direction W Width direction

Claims

1. A liquid detection sensor comprising: an optical transmission body group including a plurality of optical transmission bodies each transmitting light supplied from a light source; and a thin ribbon-shaped holder supporting the optical transmission body group, wherein the holder has a first holder element supporting one or more of the optical transmission body groups on a support surface extending in a first direction and a second direction perpendicular to the first direction, and the plurality of optical transmission bodies are arranged in the second direction.

2. The detection sensor according to claim 1, wherein the plurality of optical transmission bodies are arranged at intervals in the second direction.

3. The detection sensor according to claim 1, wherein each of the plurality of optical transmission bodies has a detection surface for detecting the liquid material, and the detection surfaces of the plurality of optical transmission bodies are offset in position in the first direction.

4. The detection sensor according to claim 3, wherein the detection surfaces of the respective plurality of optical transmitters are shifted in position in the first direction in the order in which they are arranged in the second direction.

5. The detection sensor according to claim 1, wherein each of the plurality of optical transmission bodies extends straight in the first direction or includes a portion curved from the first direction to the second direction.

6. The detection sensor according to claim 1, wherein the holder comprises a second holder element that fixes the optical transmission body to the first holder element.

7. The detection sensor according to claim 6, wherein the second holder element is provided in one or more areas of the first holder element in the first direction and across a portion or all of the area in the second direction.

8. The detection sensor according to claim 6, wherein the second holder element is provided along the first direction on both ends of the first holder element in the second direction.

9. A monitoring system for impregnated resin comprising: a resin impregnation section in which reinforcing fibers placed inside a mold are impregnated with liquid resin; a detection section which detects the impregnated resin in the resin impregnation section; and a control section which controls a monitoring operation of the impregnated resin, wherein the detection section is equipped with a detection sensor according to any one of claims 1 to 8.

10. A method for monitoring an impregnating resin, which detects the impregnation of reinforcing fibers placed inside a mold with liquid resin, comprising installing a detection sensor according to any one of claims 1 to 8 inside the mold and adjacent to the reinforcing fibers.

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