JP7724174B2 - Fluid sterilizer - Google Patents

Description

The present invention relates to a fluid sterilization device.

Fluid sterilization devices are known that sterilize fluids such as water by irradiating them with ultraviolet light. In such devices, for example, a material with high ultraviolet reflectivity is used for the inner wall surface of the flow path, and a light receiving unit is provided that measures the amount of ultraviolet light that has passed through the flow path (see, for example, Patent Document 1).

Patent No. 6810012

Causes of changes in the measurement results of ultraviolet light transmitted through the flow path include, for example, changes in the transmittance of the fluid flowing through the flow path and changes in the ultraviolet light reflectance due to dirt on the inner wall surface of the flow path. In order to properly monitor the status of the fluid sterilization device, it is desirable to be able to distinguish between multiple causes that affect the measurement results.

The present invention was made in consideration of these issues, and one of its exemplary objectives is to provide a fluid sterilization device with improved monitoring accuracy.

One embodiment of the fluid sterilization device of the present invention comprises a straight tube through which a fluid to be sterilized flows, a light source window located at a first end of the straight tube, a light source that irradiates the interior of the straight tube with ultraviolet light through the light source window, a measurement window located at a second end of the straight tube opposite the first end, and a measurement device that measures the ultraviolet light transmitted through the measurement window. The measurement device includes an optical sensor that measures the amount of ultraviolet light, a first diaphragm located between the measurement window and the optical sensor and having a first opening located on an optical axis extending from the light source toward the optical sensor, and a second diaphragm located between the first diaphragm and the optical sensor and having a second opening located on the optical axis. The measurement device is capable of satisfying the conditional expression (φ0 - φ1)/L1 ≧ (φ1 + φ2)/L2, which is expressed using a first distance L1 from the first end to the first diaphragm, a second distance L2 from the first diaphragm to the second diaphragm, an inner diameter φ0 of the straight tube at the first end, a first opening diameter φ1 of the first opening, and a second opening diameter φ2 of the second opening.

The present invention provides a fluid sterilization device with improved monitoring accuracy.

1 is a cross-sectional view schematically showing the configuration of a fluid sterilization device according to a first embodiment. FIG. 2 is a cross-sectional view schematically showing a direct light component measured by a measurement device. FIG. 10 is a cross-sectional view schematically showing the configuration of a fluid sterilization device according to a second embodiment. FIG. 10 is a cross-sectional view schematically showing the configuration of a fluid sterilizing device according to a third embodiment. FIG. 2 is a plan view schematically showing the configuration of a first aperture.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that identical elements throughout the description will be assigned the same reference numerals, and redundant explanations will be omitted where appropriate. To facilitate understanding of the description, the dimensional ratios of the components in each drawing do not necessarily correspond to the actual dimensional ratios.

(First embodiment)
1 is a diagram schematically illustrating the configuration of a fluid sterilization device 10 according to a first embodiment. The fluid sterilization device 10 irradiates a fluid flowing inside a straight pipe 12 with ultraviolet light B as indicated by arrow A to sterilize the fluid. The fluid sterilization device 10 includes the straight pipe 12, a first housing 14, a second housing 16, a light source window 18, a light source 20, a measurement window 22, a measurement device 24, and a control device 26.

The straight pipe 12 defines a processing flow path 28 through which the fluid to be sterilized flows. The processing flow path 28 is the internal space of the straight pipe 12. The straight pipe 12 has a first end 30 and a second end 32. A first housing 14 is provided at the first end 30, and a second housing 16 is provided at the second end 32. The straight pipe 12 is made of a material that is highly durable and reflective to ultraviolet light. The straight pipe 12 is made of a material that transmits ultraviolet light from the inside to the outside of the straight pipe 12. One example of such a material is a white fluororesin such as polytetrafluoroethylene (PTFE). The straight pipe 12 is made of, for example, PTFE with a sidewall 34 that is 3 mm or thicker. The inner diameter φ0 of the straight pipe 12 is not particularly limited, but may be, for example, 10 mm or larger and 500 mm or smaller, or 20 mm or larger and 100 mm or smaller. The length L0 of the straight pipe 12 is not particularly limited, but may be, for example, 100 mm or more and 1000 mm or less, or 200 mm or more and 500 mm or less.

To facilitate understanding of the drawings, the direction from the first end 30 to the second end 32 of the straight pipe 12 is also referred to as the "longitudinal direction" or "axial direction." The direction away from the central axis of the straight pipe 12 is also referred to as the "radial direction," and the direction around the central axis of the straight pipe 12 is also referred to as the "circumferential direction."

The first housing 14 defines a first communication chamber 36 and a light source chamber 38, both of which are located outside the straight tube 12. The first communication chamber 36 and the light source chamber 38 are separated by a light source window 18. The first housing 14 has a first flow port 40. The first flow port 40 opens in a direction intersecting the longitudinal direction of the straight tube 12, for example, in the radial direction. A first flow pipe 42 is connected to the first flow port 40. The first flow pipe 42 extends radially outward from the first flow port 40. The first communication chamber 36 connects the processing flow path 28 and the first flow port 40. The first communication chamber 36 communicates with the processing flow path 28 through a first gap 44 between the first end 30 of the straight tube 12 and the light source window 18 opposite the first end 30. The first communication chamber 36 is located around the entire outside circumference of the straight tube 12.

The second housing 16 defines a second communication chamber 46 and a measurement chamber 48, both of which are located outside the straight pipe 12. The second communication chamber 46 and the measurement chamber 48 are separated by a measurement window 22. The second housing 16 has a second flow port 50. The second flow port 50 opens in a direction intersecting the longitudinal direction of the straight pipe 12, for example, in the radial direction. A second flow pipe 52 is connected to the second flow port 50. The second flow pipe 52 extends radially outward from the second flow port 50. The second communication chamber 46 connects the processing flow path 28 and the second flow port 50. The second communication chamber 46 communicates with the processing flow path 28 through a second gap 54 between the second end 32 of the straight pipe 12 and the measurement window 22 opposite the second end 32. The second communication chamber 46 is located around the entire outer circumference of the straight pipe 12.

The first housing 14 and the second housing 16 are preferably made of a material that is highly durable and reflects ultraviolet light, and can be made of a fluororesin such as polyvinylidene fluoride (PVDF), for example. By using PVDF, which has a lower ultraviolet light reflectivity than PTFE, as the material for the first housing 14 and the second housing 16, ultraviolet light is reflected by the inner surfaces of the first communication chamber 36 and the second communication chamber 46, reducing the intensity of ultraviolet light traveling outside the first housing 14 and the second housing 16 through the first flow port 40 and the second flow port 50.

In the configuration of FIG. 1, the first housing 14 is the inlet side, and the second housing 16 is the outlet side. That is, the first flow port 40 is the inlet, the first flow pipe 42 is the inlet pipe, the second flow port 50 is the outlet, and the second flow pipe 52 is the outlet pipe. In another embodiment, the inlet and outlet sides may be reversed. That is, the first flow port 40 may be the outlet, the first flow pipe 42 may be the outlet pipe, the second flow port 50 may be the inlet, and the second flow pipe 52 may be the inlet pipe.

The light source window 18 is provided on the first end 30 side of the straight tube 12. The light source window 18 is provided between the light source 20 and the first end 30, and is arranged so as to face the first end 30 in the axial direction across a first gap 44. The light source window 18 is made of a material with high transmittance for ultraviolet light, such as quartz glass (SiO ₂ ) or sapphire (Al ₂ O ₃ ).

The light source 20 is provided in the light source chamber 38. The light source 20 includes a plurality of light-emitting elements 56 and a substrate 58. The light source 20 may further include a heat sink (not shown) for cooling the plurality of light-emitting elements 56. The light source 20 is configured to irradiate ultraviolet light B in the axial direction toward the processing flow path 28 through the light source window 18. In other words, the light source 20 irradiates ultraviolet light B into the interior of the straight tube 12 from the first end 30 toward the second end 32.

The light-emitting elements 56 are so-called UV-LEDs (Ultra Violet-Light Emitting Diodes). The light-emitting elements 56 emit ultraviolet light with a peak emission wavelength of 300 nm or less, selected from the wavelength range of 260 nm to 290 nm, which has high sterilization efficiency. Multiple light-emitting elements 56 are arranged in an array on the mounting surface of the substrate 58, and are positioned so that ultraviolet light B is emitted in the axial direction. The multiple light-emitting elements 56 are arranged in a two-dimensional array at equal intervals on the mounting surface of the substrate 58, which may be, for example, circular or rectangular.

The measurement window 22 is provided on the second end 32 side of the straight tube 12. The measurement window 22 is provided between the measurement device 24 and the second end 32, and is arranged so as to face the second end 32 in the axial direction across a second gap 54. Like the light source window 18, the measurement window 22 is made of a material with high transmittance for ultraviolet light, such as quartz glass (SiO ₂ ) or sapphire (Al ₂ O ₃ ).

The measuring device 24 is provided in the measuring chamber 48. The measuring device 24 measures the ultraviolet light that passes through the processing flow path 28 and is transmitted through the measuring window 22. The measuring device 24 includes a first aperture 60, a second aperture 62, and an optical sensor 64. The measuring device 24 is arranged on the optical axis C. The optical axis C extends from the light source 20 toward the optical sensor 64. The optical axis C, for example, coincides with the central axis of the straight pipe 12. The optical axis C does not have to coincide exactly with the central axis of the straight pipe 12; it may be set radially offset from the central axis of the straight pipe 12, or may be set at an angle with respect to the central axis of the straight pipe 12.

The first aperture 60 is positioned near the measurement window 22. The first aperture 60 is positioned, for example, adjacent to the measurement window 22. The first aperture 60 may also be positioned away from the measurement window 22. The first aperture 60 has a first opening 66 positioned on the optical axis C. Of the ultraviolet light passing through the measurement window 22, the first aperture 60 passes ultraviolet light in a region that overlaps with the first opening 66 on the optical axis C, and blocks ultraviolet light in a region that does not overlap with the first opening 66.

The opening diameter φ1 of the first opening 66 (also referred to as the first opening diameter φ1) is smaller than the inner diameter φ0 of the straight pipe 12. The first opening diameter φ1 is, for example, 0.1% to 50% of the inner diameter φ0 of the straight pipe 12, and may be 1% to 20%. The first opening diameter φ1 is, for example, 0.1 mm to 20 mm, and may be 1 mm to 10 mm.

The second aperture 62 is positioned near the optical sensor 64 and spaced apart from the first aperture 60. The second aperture 62 is positioned, for example, adjacent to the measurement surface 70 of the optical sensor 64. The second aperture 62 may also be positioned spaced apart from the measurement surface 70 of the optical sensor 64. The second aperture 62 has a second opening 68 positioned on the optical axis C. Of the ultraviolet light passing through the first opening 66 of the first aperture 60, the second aperture 62 passes ultraviolet light in a region that overlaps with the second opening 68 on the optical axis C, and blocks ultraviolet light in a region that does not overlap with the second opening 68.

The opening diameter φ2 of the second opening 68 (also referred to as the second opening diameter φ2) is smaller than the inner diameter φ0 of the straight pipe 12. The second opening diameter φ2 is, for example, 0.1% to 50% of the inner diameter φ0 of the straight pipe 12, and may be 1% to 20%. The second opening diameter φ2 is, for example, 0.1 mm to 20 mm, and may be 1 mm to 10 mm. The second opening diameter φ2 may be the same as the first opening diameter φ1. The second opening diameter φ2 may be smaller than the first opening diameter φ1 or larger than the first opening diameter φ1.

The optical sensor 64 has a measurement surface 70 and measures the amount of ultraviolet light incident on the measurement surface 70. The optical sensor 64 includes, for example, a photodiode capable of detecting ultraviolet light. Of the ultraviolet light that passes through the measurement window 22, the optical sensor 64 measures only the ultraviolet light that passes through the first opening 66 and the second opening 68. The measurement results of the optical sensor 64 are sent to the control device 26.

The measuring device 24 is configured to satisfy the following conditional expression (1), which is expressed using a first distance L1 from the first end 30 to the first orifice 60, a second distance L2 from the first orifice 60 to the second orifice 62, an inner diameter φ0 of the straight pipe 12 at the first end 30, a first opening diameter φ1, and a second opening diameter φ2.
(φ0-φ1)/L1≧(φ1+φ2)/L2…(1)
In the example of Figure 1, the first distance L1 corresponds to the sum of the axial length L0 of the straight pipe 12, the axial width d of the second gap 54, and the thickness t of the measurement window 22, and L1 = L0 + d + t.

By configuring the measurement device 24 to satisfy the above conditional expression (1), it is possible to measure only the direct light component of the ultraviolet light B emitted from the light source 20 that reaches the optical sensor 64 without being reflected by the inner surface 72 of the straight tube 12. In other words, the first aperture 60 and the second aperture 62 can be used to block the reflected light component of the ultraviolet light B emitted from the light source 20 that is reflected at least once by the inner surface 72 of the straight tube 12 before reaching the measurement window 22.

Figure 2 is a cross-sectional view schematically illustrating the direct light component 74 measured by the measuring device 24. For ease of explanation, Figure 2 shows only some of the components of the fluid sterilization device 10 shown in Figure 1. The direct light component 74, indicated by the shaded area in Figure 2, is the light component of the ultraviolet light emitted from the light source 20 that passes through the first opening 66 without being reflected by the inner surface 72 of the straight tube 12. The second opening 68 has a second opening diameter φ2 and a second distance L2 set so as to pass at least a portion of the direct light component 74 that passes through the first opening 66 and to block the reflected light component 76, which is different from the direct light component 74.

From the geometrical arrangement shown in FIG. 2, the following equation (2) holds for the diameter φ3 of the direct light component 74 incident on the second diaphragm 62.
(φ0-φ1)/L1=(φ1+φ3)/L2...(2)
In order for the second aperture 68 to pass at least a portion of the direct light component 74, the second aperture system φ2 should be set so that the diameter of the direct light component 74 incident on the second diaphragm 62 is equal to or smaller than φ3 (i.e., φ3≧φ2). By substituting φ3≧φ2 into the above equation (2), the above conditional equation (1) can be obtained.

By modifying the above conditional expression (1), the following expression (3) regarding the second distance L2 is obtained.
L2≧L1×(φ1+φ2)/(φ0−φ1)…(3)
As an example, if φ0 = 30 mm, φ1 = 5 mm, and φ2 = 5 mm, the relationship between the first distance L1 and the second distance L2 is L2 ≧ L1 × 0.4, and the second distance L2 should be set to 40% or more of the first distance L1. For example, if L1 = 300 mm, L2 should be set to 120 mm or more. Note that, from the perspective of increasing the amount of direct light component 74 measured by the optical sensor 64, it is preferable to make the second distance L2 as small as possible within a range that satisfies the above conditional expression (1). The second distance L2 is preferably, for example, no more than twice L1 × (φ1 + φ2) / (φ0 - φ1), and may be no more than 1.5, 1.2, or 1.1 times.

By modifying the above conditional expression (1), the following expression (4) regarding the first opening diameter φ1 is obtained.
φ1≦(L2×φ0−L1×φ2)/(L1+L2)…(4)
As an example, if L1 = 300 mm, L2 = 60 mm, φ0 = 30 mm, and φ2 = 4 mm, then φ1 ≦ 1.66 mm. From the viewpoint of increasing the amount of direct light component 74 measured by optical sensor 64, it is preferable to make first opening diameter φ1 as large as possible within a range that satisfies conditional expression (4). For example, first opening diameter φ1 is preferably 0.5 or greater of (L2 × φ0 - L1 × φ2) / (L1 + L2), and may be 0.8 or greater, 0.9 or greater, or 0.95 or greater.

By modifying the above conditional expression (1), the following expression (5) regarding the second opening diameter φ2 is obtained.
φ2≦{L2×φ0−(L1+L2)×φ1}/L1…(5)
As an example, if L1 = 300 mm, L2 = 60 mm, φ0 = 30 mm, and φ1 = 1 mm, then φ2 ≦ 4.8 mm. From the viewpoint of increasing the amount of direct light component 74 measured by optical sensor 64, it is preferable to make second opening diameter φ2 as large as possible within a range that satisfies conditional expression (5). For example, second opening diameter φ2 is preferably 0.5 or greater of {L2 × φ0 - (L1 + L2) × φ1}/L1, and may be 0.8 or greater, 0.9 or greater, or 0.95 or greater.

If the first opening diameter φ1 and the second opening diameter φ2 are the same, the following formula (6) is obtained.
φ1=φ2≦φ0×L2/(2×L1+L2) …(6)
As an example, if L1 = 300 mm and L2 = 60 mm, then φ1 = φ2 ≦ φ0 × 1/11, and the first opening diameter φ1 and the second opening diameter φ2 may be set to 1/11 or less of the inner diameter φ0 of the straight pipe 12. For example, if φ0 = 30 mm, then the first opening diameter φ1 and the second opening diameter φ2 may be set to 2.72 mm or less. Note that, from the viewpoint of increasing the amount of direct light component 74 measured by the optical sensor 64, it is preferable to make the first opening diameter φ1 and the second opening diameter φ2 as large as possible within a range that satisfies the above conditional expression (6). The first opening diameter φ1 and the second opening diameter φ2 are preferably equal to or greater than 0.5 of φ0 × L2/(2 × L1 + L2), and may be equal to or greater than 0.8, 0.9, or 0.95.

The control device 26 includes, for example, an integrated circuit such as an MCU (Micro Controller Unit). In terms of hardware, the control device 26 can be realized using elements and mechanical devices such as a computer's CPU and memory, and in terms of software, it can be realized using a computer program, etc. Those skilled in the art will understand that the control device 26 can be realized in various ways by combining hardware and software.

The control device 26 controls the operation of the light source 20 using the measurement results of the measuring device 24. When the fluid sterilization device 10 is operating, that is, when fluid is flowing through the treatment flow path 28, the control device 26 drives the light source 20 so that the measurement results of the optical sensor 64 reach a predetermined value. This ensures that ultraviolet light of the desired intensity is irradiated onto the fluid flowing through the treatment flow path 28.

The control device 26 calculates the transmittance of the fluid using the measurement results of the direct light component 74 measured by the measurement device 24. The control device 26 calculates the transmittance T = Ib/Ia, for example, using the measurement result Ia of the optical sensor 64 when the fluid sterilization device 10 is not operating and the measurement result Ib of the optical sensor 64 when the fluid sterilization device 10 is operating. The measurement result Ia when the fluid sterilization device 10 is not operating is a reference value for calculating the transmittance T. The reference value Ia may be measured when no fluid is present inside the processing flow path 28, or when a fluid with a known transmittance (e.g., uncontaminated pure water) is present inside the processing flow path 28. The reference value Ia may be measured in an initial state before the fluid sterilization device 10 is first used, or at any time after the fluid sterilization device 10 is first used.

The control device 26 may calculate the absorption coefficient α of the fluid using the formula: transmittance T = exp(-αL). Here, the path length L is the length of the processing flow path 28, and may be, for example, the length L0 of the straight pipe 12. Note that the path length L may also be the sum L0 + 2d of the length L0 of the straight pipe 12, the width d of the first gap 44, and the width d of the second gap 54.

In this embodiment, the measuring device 24 can measure the amount of light of only the direct light component 74, thereby improving the accuracy of calculating the fluid transmittance T based on the measurement results of the measuring device 24. If the measuring device 24 does not include the first diaphragm 60 and the second diaphragm 62, the optical sensor 64 measures the total amount of light of the direct light component 74 and the reflected light component 76. Because the reflected light component 76 is reflected by the inner surface 72 of the straight pipe 12, it is affected by changes in reflectance due to contamination on the inner surface 72. Furthermore, because the reflected light component 76 travels obliquely through the processing flow path 28 with respect to the optical axis C, it takes a longer path through the fluid than the direct light component 74 and is therefore more affected by changes in the fluid's transmittance. On the other hand, because the direct light component 74 travels along the optical axis C through the processing flow path 28, there is less variation in the path length it takes through the fluid. Therefore, when the absorption coefficient α is calculated using T = exp(-αL), errors in the absorption coefficient α that may arise due to variations in the path length L can be reduced.

Second Embodiment
3 is a cross-sectional view showing a schematic configuration of a fluid sterilization device 10A according to a second embodiment. The second embodiment differs from the first embodiment in that a measuring device 24A is configured so that the second distance L2 is variable. The following description of the second embodiment will focus on the differences from the first embodiment, and commonalities will be omitted as appropriate.

The fluid sterilization device 10A comprises a straight pipe 12, a first housing 14, a second housing 16, a light source window 18, a light source 20, a measurement window 22, a measurement device 24A, and a control device 26A. The straight pipe 12, the first housing 14, the second housing 16, the light source window 18, the light source 20, and the measurement window 22 are configured in the same manner as in the first embodiment.

The measuring device 24A includes a first aperture 60, a second aperture 62, an optical sensor 64, and a drive mechanism 80A. The first aperture 60, the second aperture 62, and the optical sensor 64 are configured in the same manner as in the first embodiment.

The drive mechanism 80A moves the second aperture 62 and the optical sensor 64 along the optical axis C, varying the second distance L2 from the first aperture 60 to the second aperture 62. The drive mechanism 80A may be configured to move only the second aperture 62 without moving the optical sensor 64. The drive mechanism 80A may also be configured to bring the first aperture 60 and the second aperture 62 into contact, thereby making the second distance L2 substantially zero.

The drive mechanism 80A is configured to vary the second distance L2 between a first state that satisfies the above conditional formula (1) and a second state that does not satisfy the above conditional formula (1) by moving at least the second aperture 62. According to the above formula (3), the first state can be achieved by increasing the second distance L2, and the second state can be achieved by decreasing the second distance L2. The first state may be a state in which the second distance L2 is maximum within the range in which the second distance L2 is variable by the drive mechanism 80A. The second state may be a state in which the second distance L2 is minimum within the range in which the second distance L2 is variable by the drive mechanism 80A.

The control device 26A controls the operation of the drive mechanism 80A. The control device 26A acquires the first measurement result I1b measured by the optical sensor 64 in the first state when the fluid sterilization device 10A is operating. The control device 26A may use the first measurement result I1b to calculate the transmittance T and absorption coefficient α of the fluid. The control device 26A may use the measurement result I1a (also referred to as the first reference value I1a) measured by the optical sensor 64 in the first state when the fluid sterilization device 10A is not operating to calculate the transmittance T = I1b/I1a. The control device 26A may calculate the absorption coefficient α of the fluid using the transmittance T = I1b/I1a = exp(-αL).

The control device 26A further acquires a second measurement result I2b measured by the optical sensor 64 in the second state when the fluid sterilization device 10A is operating. The control device 26A may use the first measurement result I1b and the second measurement result I2b to detect dirt adhering to the inner surface 72 of the straight pipe 12. Because the second measurement result I2b includes a direct light component 74 and a reflected light component 76, the second measurement result I2b can be used to evaluate the contribution of changes in reflectance caused by dirt on the inner surface 72 of the straight pipe 12, which is included in the reflected light component 76.

For example, the differential measurement value ΔIb=I2b−I1b obtained by subtracting the first measurement result I1b from the second measurement result I2b mainly includes the reflected light component 76. The differential measurement value ΔIb can be expressed by the following equation (7) using the differential reference value ΔIa=I2a−I1a obtained by subtracting the first reference value I1a from the second reference value I2a.
ΔIb=ΔIa×exp(-αkL)×β…(7)
Here, the second reference value I2a is the measurement result measured by the optical sensor 64 in the second state when the fluid sterilization device 10A is not operating, and is the reference value for the second state. The absorption coefficient α is calculated using the first measurement result I1b. The coefficient k is the ratio of the path length kL of the reflected light component 76 to the path length L of the direct light component 74, where k≧1. The coefficient β represents a change in reflectance due to contamination of the inner surface 72 of the straight pipe 12. The coefficient k can be calculated in advance, for example, by flowing fluids with known absorption coefficients α1 and α2 through the treatment flow path 28 and obtaining the differential measurement value ΔIb in a state where the inner surface 72 of the straight pipe 12 is not contaminated and the coefficient β can be assumed to be 1.

The control device 26A may use the calculated coefficient β to detect the presence or absence of contamination on the inner surface 72 of the straight pipe 12. The control device 26A may detect contamination on the inner surface 72 of the straight pipe 12 when the coefficient β is equal to or less than a predetermined threshold value.

According to this embodiment, by using the second measurement result I2b, it is possible to improve the calculation accuracy of the coefficient β, which represents the change in reflectance due to contamination on the inner surface 72 of the straight pipe 12. According to this embodiment, it is possible to more appropriately detect whether or not the inner surface 72 of the straight pipe 12 is contaminated.

(Third embodiment)
4 is a diagram showing a schematic configuration of a fluid sterilization device 10B according to a third embodiment. The third embodiment differs from the above-described embodiments in that a measuring device 24B is configured so that the first opening diameter φ1 is variable. The following description of the third embodiment will focus on the differences from the above-described embodiments, and omit the commonalities as appropriate.

The fluid sterilization device 10B comprises a straight pipe 12, a first housing 14, a second housing 16, a light source window 18, a light source 20, a measurement window 22, a measurement device 24B, and a control device 26B. The straight pipe 12, the first housing 14, the second housing 16, the light source window 18, the light source 20, and the measurement window 22 are configured in the same manner as in the first embodiment.

The measuring device 24B includes a first aperture 60B, a second aperture 62, an optical sensor 64, and a drive mechanism 80B. The second aperture 62 and the optical sensor 64 are configured in the same manner as in the first embodiment.

The first aperture 60B has a fixed plate 82 with a fixed hole and a movable plate 84 with a movable hole. The movable plate 84 is positioned so as to overlap with the fixed plate 82 in the direction of optical axis C. The first opening 66B is formed by communication between the fixed hole provided in the fixed plate 82 and the movable hole provided in the movable plate 84. The movable plate 84 has multiple movable holes with different opening diameters. The drive mechanism 80B is configured to move the movable plate 84 relative to the fixed plate 82 and switch the movable hole that communicates with the fixed hole.

Figure 5 is a plan view schematically illustrating the configuration of the first aperture 60B. The fixed plate 82 has a fixed hole 86 located at a position overlapping the optical axis C. The movable plate 84 has a first movable hole 88 and a second movable hole 90. The opening diameter φ11 of the first movable hole 88 is smaller than the opening diameter φ12 of the second movable hole 90. The drive mechanism 80B slides the movable plate 84 relative to the fixed plate 82 as indicated by arrow X, switching between a first state in which the fixed hole 86 and the first movable hole 88 are in communication with each other and a second state in which the fixed hole 86 and the second movable hole 90 are in communication with each other. The opening diameter of the fixed hole 86 is larger than the opening diameters φ11 and φ12 of the first movable hole 88 and the second movable hole 90. Therefore, the first opening diameter φ1 of the first aperture 66B is determined by the opening diameters φ11 and φ12 of the first movable hole 88 or the second movable hole 90.

The drive mechanism 80B is configured to vary the first opening diameter φ1 between a first state that satisfies the above conditional formula (1) and a second state that does not satisfy the above conditional formula (1). According to the above formula (4), the first state can be achieved by reducing the first opening diameter φ1, and the second state can be achieved by increasing the first opening diameter φ1. The opening diameter φ11 of the first movable hole is set to satisfy the above formula (4), such that φ11≦(L2×φ0−L1×φ2)/(L1+L2). On the other hand, the opening diameter φ12 of the second movable hole is set to not satisfy the above formula (4), such that φ12>(L2×φ0−L1×φ2)/(L1+L2).

The control device 26B controls the operation of the drive mechanism 80B. The control device 26B acquires a first measurement result I1b measured by the optical sensor 64 in the first state and a second measurement result I2b measured by the optical sensor 64 in the second state during operation of the fluid sterilization device 10B. Using the first measurement result I1b and the second measurement result I2b, the control device 26B can calculate the fluid transmittance T, the fluid absorption coefficient α, and a coefficient β representing the degree of contamination on the inner surface 72 of the straight pipe 12. Therefore, this embodiment can also achieve the same effects as the second embodiment.

The first aperture 60B may be configured so that the first opening diameter φ1 is variable using a configuration different from that shown in FIG. 5. For example, the first aperture 60B may be configured so that the movable holes 88, 90 communicating with the fixed hole 86 are switched by rotating the movable plate 84 instead of sliding it. The first aperture 60B may be configured so that the first opening diameter φ1 is continuously variable, or may be an iris aperture using multiple aperture blades.

As a modified example of the third embodiment, instead of varying the first aperture diameter φ1 of the first aperture 60B, the second aperture diameter φ2 of the second aperture 62 may be varied. In this case, the second aperture 62 may have a configuration similar to that of the first aperture 60B. The drive mechanism 80B may be configured to vary the second aperture diameter φ2 between a first state that satisfies the above conditional formula (1) and a second state that does not satisfy the above conditional formula (1). From the above formula (5), the first state can be achieved by reducing the second aperture diameter φ2, and the second state can be achieved by increasing the second aperture diameter φ2.

The present invention has been described above based on examples. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, and that various design changes and modifications are possible, and that such modifications are also within the scope of the present invention.

Several aspects of the present invention are described below.

A first aspect of the present invention comprises a straight pipe through which a fluid to be sterilized flows, a light source window disposed at a first end of the straight pipe, a light source that irradiates the interior of the straight pipe with ultraviolet light through the light source window, a measurement window disposed at a second end of the straight pipe opposite the first end, and a measurement device that measures the ultraviolet light that has passed through the measurement window, the measurement device comprising an optical sensor that measures the amount of ultraviolet light, and a first optical fiber disposed between the measurement window and the optical sensor and positioned on an optical axis extending from the light source toward the optical sensor. The fluid sterilization device includes a first diaphragm having an opening, and a second diaphragm having a second opening disposed on the optical axis and disposed between the first diaphragm and the optical sensor, and is capable of satisfying the conditional expression (φ0-φ1)/L1≧(φ1+φ2)/L2, which is expressed using a first distance L1 from the first end to the first diaphragm, a second distance L2 from the first diaphragm to the second diaphragm, an inner diameter φ0 of the straight tube at the first end, a first opening diameter φ1 of the first opening, and a second opening diameter φ2 of the second opening. According to the first aspect, by configuring the measurement device to satisfy the conditional expression, only the direct light component that transmits through the straight tube can be measured, and the reflected light component reflected by the inner surface of the straight tube can be excluded from the measurement target.

A second aspect of the present invention is the fluid sterilization device described in the first aspect, wherein the measurement device further includes a drive mechanism that moves the second aperture to vary the second distance L2 between a first state in which the conditional expression is satisfied and a second state in which the conditional expression is not satisfied. According to the second aspect, it is possible to switch between the first state in which the conditional expression is satisfied and the second state in which the conditional expression is not satisfied, thereby obtaining a first measurement result containing only the direct light component and a second measurement result containing the reflected light component.

A third aspect of the present invention is the fluid sterilization device described in the first aspect, wherein the measurement device further includes a drive mechanism that varies the first opening diameter φ1 between a first state that satisfies the conditional formula and a second state that does not satisfy the conditional formula. According to the third aspect, it is possible to switch between the first state that satisfies the conditional formula and the second state that does not satisfy the conditional formula, thereby obtaining a first measurement result containing only the direct light component and a second measurement result containing the reflected light component.

A fourth aspect of the present invention is the fluid sterilization device described in the first aspect, wherein the measurement device further includes a drive mechanism that varies the second opening diameter φ2 between a first state that satisfies the conditional formula and a second state that does not satisfy the conditional formula. According to the fourth aspect, it is possible to switch between the first state that satisfies the conditional formula and the second state that does not satisfy the conditional formula, thereby obtaining a first measurement result containing only the direct light component and a second measurement result that contains the reflected light component.

A fifth aspect of the present invention is a fluid sterilization device according to any one of the first to fourth aspects, further comprising a control device that calculates the transmittance of the fluid flowing inside the straight pipe using the measurement results obtained by the optical sensor when the conditional expression is satisfied. According to the fifth aspect, the transmittance of the fluid is calculated using the measurement results of only the direct light component that passes through the inside of the straight pipe, thereby improving the accuracy of the transmittance calculation.

A fifth aspect of the present invention is a fluid sterilization device according to any one of the second to fourth aspects, further comprising a control device that detects dirt adhering to the inner surface of the straight pipe using a first measurement result measured by the optical sensor in the first state and a second measurement result measured by the optical sensor in the second state. According to the sixth aspect, the accuracy of detecting dirt adhering to the inner surface can be improved by using a first measurement result containing only a direct light component and a second measurement result containing a reflected light component.

10, 10A, 10B...fluid sterilization device, 12...straight tube, 18...light source window, 20...light source, 22...measuring window, 24, 24A, 24B...measuring device, 26, 26A, 26B...control device, 30...first end, 32...second end, 60, 60B...first aperture, 62...second aperture, 64...optical sensor, 66, 66B...first opening, 68...second opening, 72...inner surface, 80A, 80B...driving mechanism.

Claims (6)

a straight pipe through which a fluid to be sterilized flows;
a light source window disposed on a first end side of the straight tube;
a light source that irradiates ultraviolet light into the inside of the straight tube through the light source window;
a measurement window disposed on a second end side of the straight pipe opposite to the first end side;
a measurement device that measures the ultraviolet light that has passed through the measurement window,
The measuring device is
an optical sensor that measures the amount of ultraviolet light;
a first diaphragm provided between the measurement window and the optical sensor, the first diaphragm having a first opening disposed on an optical axis extending from the light source toward the optical sensor;
a second diaphragm provided between the first diaphragm and the optical sensor, the second diaphragm having a second opening disposed on the optical axis;
A fluid sterilization device that can satisfy the conditional formula (φ0-φ1)/L1≧(φ1+φ2)/L2, which is expressed using a first distance L1 from the first end to the first orifice, a second distance L2 from the first orifice to the second orifice, an inner diameter φ0 of the straight pipe at the first end, a first opening diameter φ1 of the first opening, and a second opening diameter φ2 of the second opening. The fluid sterilization device described in claim 1, wherein the measurement device further includes a drive mechanism that moves the second aperture to vary the second distance L2 between a first state in which the conditional expression is satisfied and a second state in which the conditional expression is not satisfied. The fluid sterilizing device described in claim 1, wherein the measuring device further includes a drive mechanism that varies the first opening diameter φ1 between a first state in which the conditional expression is satisfied and a second state in which the conditional expression is not satisfied. The fluid sterilizing device described in claim 1, wherein the measuring device further includes a drive mechanism that varies the second opening diameter φ2 between a first state in which the conditional expression is satisfied and a second state in which the conditional expression is not satisfied. The fluid sterilization device according to any one of claims 1 to 4, further comprising a control device that calculates the ultraviolet light transmittance of the fluid flowing inside the straight pipe using the measurement result measured by the optical sensor when the conditional formula is satisfied. The fluid sterilization device described in any one of claims 2 to 4, further comprising a control device that detects dirt adhering to the inner surface of the straight pipe using a first measurement result measured by the optical sensor in the first state and a second measurement result measured by the optical sensor in the second state.