JP2012063328A - Liquid sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain suitable detection sensitivity to an air bubble and a droplet.SOLUTION: The present invention relates to a liquid sensor which optically detects a liquid in a translucent tube. The liquid sensor includes two optical systems which detect whether there is the liquid in the translucent tube respectively at two places which are apart from each other in a length direction of the translucent tube. The interval between the two places is set to be longer than a typical length of an air bubble appearing in the translucent tube when a liquid supply source does not run out of the liquid and within a range of a typical length of the air bubble appearing when the liquid supply source runs out of the liquid.

Description

  The present invention relates to a liquid sensor that optically detects the presence or absence of liquid in a translucent tube.

  Widely used liquid sensors that detect the liquid in the tube by detecting the light that enters through the side of the translucent infusion tube and detects the light that is transmitted through the tube or refracted (or reflected) on the inner wall of the tube Has been. As such a liquid sensor, for example, as described in Patent Document 1, it is detected whether there is liquid in the light-transmitting tube according to the intensity of light transmitted through the light-transmitting tube. There is.

  In the liquid detection device described in Patent Document 1, sensor light is incident substantially perpendicularly to the central axis of the translucent tube, and light that passes straight through the translucent tube is detected by the light receiving unit. The transparent liquid filled in the cylindrical translucent tube acts as a kind of lens with respect to the sensor light incident perpendicularly to the translucent tube and converges the light. In addition, since the resin forming the translucent tube has a refractive index close to that of the liquid, when the translucent tube is filled with the liquid, the light is not reflected by the inner wall surface of the translucent tube. Therefore, when there is a liquid in the translucent tube, the sensor light passes straight through the translucent tube, and strong sensor light is detected by the light receiving unit. On the other hand, when there is no liquid in the translucent tube, no lens action occurs, so the sensor light diverges in the translucent tube and reflects off the inner wall surface. It will be extremely weak. Thus, based on the intensity | strength of the sensor light which a light-receiving part detects, the presence or absence of the liquid in a translucent tube can be determined.

JP 2001-336966 A

  By the way, air bubbles often appear in the liquid of the infusion tube. This is a deposit of gas dissolved in the liquid mainly due to liquid temperature fluctuations. In addition, in a highly viscous liquid or a liquid such as a detergent in which bubbles are present stably, bubbles generated when stirred together with the gas during transportation or the like may remain in the liquid. Such bubbles are relatively small, and generally have a size of about a few millimeters from the visual limit.

  In addition, the liquid remaining attached to the inner wall forms droplets on the inner wall surface of the infusion tube that has been emptied through the removal of the internal liquid.

  Such bubbles and droplets can cause erroneous detection. Since the conventional liquid sensor as described in Patent Document 1 detects the liquid only at one place of the infusion tube, it is difficult to avoid erroneous detection due to bubbles or droplets.

  On the other hand, in some uses such as medical use and fine chemical use, the inclusion of bubbles as described above is strictly limited, and it is required to detect bubbles with higher accuracy.

  The present invention has been made in view of the above circumstances, and according to an embodiment of the present invention, a liquid sensor having appropriate sensitivity to bubbles and droplets is provided.

  According to the embodiment of the present invention, a liquid sensor for optically detecting a liquid in a translucent tube is provided. The liquid sensor according to the embodiment of the present invention includes two optical systems that detect the presence / absence of liquid in the translucent tube, respectively, at two locations separated in the length direction of the translucent tube. The distance between the two locations is longer than the typical length of bubbles appearing in the translucent tube when the liquid source is not running out of liquid, and is within the range of the typical length of bubbles appearing when running out of liquid. It is set to be.

  The liquid sensor according to the embodiment of the present invention includes two optical systems that detect a liquid, thereby suppressing erroneous detection due to bubbles. In particular, by reducing the distance between the detection points of the two optical systems longer than the length of the bubbles that often appear in the tube when the liquid is not running out, the possibility that the two optical systems will falsely detect at the same time is reduced. Can do. In addition, by setting the interval between the detection points within the range of the length of large bubbles that often appear in the tube when the liquid runs out, it is possible to detect large bubbles that are a sign of liquid running out.

  The above spacing is 15 mm or more, and one typical spacing is 15 mm. Moreover, it is desirable that the distance is 20 mm or more, and the optimum value of the distance in some embodiments is 20 mm.

  In the above configuration, it is desirable to determine that there is liquid when at least one of the two optical systems detects liquid, and to determine that there is no liquid when neither of the two optical systems detects liquid. .

  Such determination makes it possible to accurately and quickly detect a large bubble that is a sign of liquid shortage or a liquid shortage while suppressing erroneous detection due to small bubbles not related to liquid shortage.

You may provide the 3 or more optical system which detects the presence or absence of the liquid in a translucent tube in each of the three or more places distant in the length direction of the translucent tube.
By providing a large number of optical systems, it is possible to more accurately determine whether the liquid has run out.

  Preferably, each of the two optical systems includes a light source and a light receiving element, and a light beam emitted from the light source is incident on the translucent tube from a side surface perpendicular to the central axis of the translucent tube. In this case, when there is liquid in the translucent tube at the location where the light beam is incident, the light beam passes straight through the translucent tube and is detected by the light receiving element. When there is no liquid in the translucent tube, the light beam is refracted or reflected by the inner wall of the translucent tube and is not detected by the light receiving element.

  In such a configuration, the time when the light receiving element does not output a detection signal corresponds to an abnormal (liquid running out) state. Therefore, even when the detection signal is not output due to a failure of the optical element or the like, it is determined as an abnormal state, and thus erroneous determination due to a failure or malfunction of the apparatus is prevented.

Typically, the light source and the light receiving element of the optical system are arranged so that the light emitting surface and the light receiving surface face each other through a light-transmitting tube.
With such an arrangement, an optical system with a simple configuration that does not require deflecting means such as a mirror is realized.

  In addition, it is desirable that the light receiving elements of the two optical systems are arranged with the light receiving surfaces in opposite directions.

  With this configuration, the possibility of erroneous detection of light from another optical system can be greatly reduced. When three or more optical systems are provided, it is desirable to reverse the direction of the light receiving surface between adjacent optical systems.

  The liquid sensor according to the embodiment of the present invention covers a part of a light-transmitting tube including a light source and a light-receiving element, and a part of the light-transmitting tube, and shields it from external light. It is desirable to provide an attachment for positioning and attaching the tube. Further, in this case, the main body includes a light shielding member that covers the light source and the light receiving element and shields from external light, and the attachment and the light shielding member are formed with two pairs of openings for allowing the light flux to pass therethrough at the above-described interval. Is desirable. In the above configuration, it is desirable that a pair of attachment openings and a pair of light shielding member openings be disposed between the light emitting surface and the light receiving surface of each optical system.

  When the attachment having the above-described configuration is employed, the attachment / detachment of the liquid sensor and the replacement of the translucent tube are facilitated. Such an attachment is provided with a function of shielding the detection location of the translucent tube from outside light causing erroneous detection and a function of accurately positioning the translucent tube with respect to the optical element accommodated in the main body. This makes it possible to achieve both ease of attachment and removal and excellent detection accuracy. In order to secure an optical path connecting the optical element of the main body and the translucent tube while maintaining the light shielding property, it is effective to provide an opening in the shielding object on the optical path.

The opening may be a slit that gives a diametrical projection to the translucent tube.
The slit can be processed more easily than the round hole. In addition, when condensing the light beam on the tube with a lens, it is necessary to widen the opening. However, if the opening is expanded biaxially (planarly), the light shielding effect is significantly reduced, so that the opening is expanded uniaxially. A slit shape is desirable. In this case, it is desirable to collect the light beam by a cylindrical lens.

  According to the embodiment of the present invention, a liquid sensor having appropriate sensitivity to bubbles and droplets is provided.

1 is a perspective view schematically showing an external appearance of a liquid sensor according to an exemplary embodiment of the present invention. It is a disassembled perspective view which shows schematically the internal structure of the liquid sensor which concerns on exemplary embodiment of this invention. FIG. 3 is a three-sided view schematically illustrating an appearance of a liquid sensor according to an exemplary embodiment of the present invention. It is sectional drawing which shows schematically the internal structure of the liquid sensor which concerns on exemplary embodiment of this invention. It is a block diagram which shows schematic structure of the circuit unit of the liquid sensor which concerns on exemplary embodiment of this invention. It is an external view which shows the state which fixed the tube using the binding band. It is an exploded view explaining the mounting method of the tube adjuster which concerns on embodiment of this invention. It is a perspective view which shows roughly the external appearance of the tube adjuster which concerns on embodiment of this invention.

  Hereinafter, a liquid sensor 1 according to an exemplary embodiment of the present invention will be described in detail with reference to the drawings. The liquid sensor 1 is a sensor that optically detects the presence or absence of liquid in the translucent tube T. The liquid sensor 1 is, for example, installed in the middle of an infusion tube in a liquid supply apparatus used for supplying cleaning liquid to a cleaning apparatus, and used for detecting liquid shortage in a liquid storage tank in which the supplied liquid is stored. The In addition, when this liquid sensor is installed at a predetermined height of the piping connecting the bottom and top of the storage tank, the liquid level in the tank (whether the liquid level is higher / lower than the mounting height of the liquid sensor) ) Can also be detected.

  FIG. 1 is a perspective view schematically showing the external appearance of a liquid sensor 1 according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view schematically showing the internal structure of the liquid sensor 1. Further, a three-view diagram schematically showing the appearance of the liquid sensor 1 is shown in FIG. FIG. 4 is a cross-sectional view schematically showing the internal structure of the liquid sensor 1. 3A is a plan view seen from the Z-axis direction (see FIG. 1), FIG. 3B is a front view seen from the Y-axis direction (see FIG. 1), and FIG. ) Is a side view seen from the X-axis direction (see FIG. 1), which is the length direction of the translucent tube T. 4A, 4B, and 4C are cross-sectional views taken along lines AA, BB, and CC in FIG. 3A, respectively.

  The liquid sensor 1 includes a main body 100 and an attachment 200. The main body 100 houses a circuit unit 30 on which optical elements (a light source 34 and a light receiving element 35) for detecting liquid are mounted. The attachment 200 is a member for shielding the liquid detection portion of the translucent tube T from outside light and accurately positioning and holding the translucent tube T with respect to the optical system of the main body 100. In order to make it easy to replace the translucent tube T, the attachment 200 is configured to be easily detachable from the main body 100, and the attachment is also configured to be detachable from the translucent tube T.

  In the following description, according to the coordinate axes shown in FIG. 1, the length direction of the translucent tube T is the X-axis direction, the direction perpendicular to the bottom surface (mounting surface) of the main body 100 is the Z-axis direction, the X-axis direction, and A direction perpendicular to both the Z-axis direction is referred to as a Y-axis direction. Also, the Z-axis positive direction (arrow direction in the figure) is called “up”, and the Z-axis negative direction (reverse direction of the arrow) is called “down”. The expressions “upper” and “lower” are used for convenience of description in order to easily identify the arrangement relationship of each element. In a situation where the liquid sensor 1 is actually used, these directions are It does not necessarily coincide with the vertical direction. In other words, the liquid sensor 1 can be arranged with the Z-axis direction shown in the drawing directed in an arbitrary direction (for example, the horizontal direction).

  As shown in the exploded perspective view of FIG. 2, the main body 100 of the liquid sensor 1 includes a housing 10, a packing 20, a circuit unit 30, a light shielding guide 40, and a cover 50.

  The circuit unit 30 according to the present embodiment includes two circuit boards 30a and 30b arranged in parallel at a predetermined distance from each other, and the circuit boards 30a and 30b are integrally connected by a connecting portion (not shown). Has been.

  The housing 10 is a box having an opening on the upper side and having a substantially rectangular parallelepiped shape. In order to shield the optical element housed in the housing 10 from outside light, the housing 10 is formed of a material that is substantially opaque to light in a wavelength range in which the light receiving element 35 described below has sensitivity. . The housing 10 of the present embodiment is formed from a colored resin, but the material forming the housing is not limited to this. For example, the housing 10 may be formed of a transparent resin, and the inside may be coated with a light shielding paint, or the inside of the housing 10 may be covered with a light shielding film.

  When the upper opening of the housing 10 is covered with the cover 50 via the packing 20 and the housing 10 and the cover 50 are fixed by the long screws 24, the internal space of the main body 100 surrounded by the housing 10 and the cover 50 becomes watertight, Waterproofing of the circuit unit 30 disposed inside the main body 100 is ensured.

  As shown in FIG. 4C, a cylindrical fixed column 12 protruding upward is formed on the inner bottom surface of the housing 10, and a female screw extending downward is formed at the center of the upper surface of the fixed column 12. 12h is formed. Further, a through hole 50 h that penetrates up and down is formed in the center of the cover 50. A through hole 30ah is also formed in the center of one circuit board 30a constituting the circuit unit 30. The long screw 24 is passed through the through hole 50h of the cover 50 and the through hole 30ah of the circuit board 30a, and is screwed into the female screw 12h formed on the housing 10, whereby the cover 50, the circuit unit 30 and the housing 10 are integrated. The cover 50 is brought into close contact with the housing 10.

  By the way, in this embodiment, the cover 50 is formed from the transparent resin which has the high transmittance | permeability with respect to the wavelength of a light source as opposed to the housing | casing 10 having light-shielding property. In the present embodiment, in order to reliably waterproof the circuit unit 30 including the optical element, the circuit unit 30 is disposed inside the water-tight main body 100, and the translucent tube T that may leak is disposed on the main body 100. An external arrangement is adopted. Therefore, the cover 50 is formed of a material having a light transmitting property with respect to the monitor light 50 so that the liquid in the light transmitting tube T can be detected through the cover 50. As the transparent resin material for forming the cover 50, conventionally used acrylic resin such as polycarbonate (PC) resin and PMMA (polymethylmethacrylate) can be used, but sufficient optical characteristics and mechanical characteristics are obtained. In addition, a polysulfone (PSU) resin excellent in chemical resistance and heat resistance is most suitable.

  Moreover, in this embodiment, the housing | casing 10 is also formed from PSU resin. However, the PSU resin used for the housing 10 is added with a colorant having high absorption in a wavelength range where the light receiving element 35 is sensitive, so that the optical element is shielded from external light. . Thus, by forming the cover 50 and the casing 10 constituting the sealed container of the main body 100 from PSU resin having excellent heat resistance, the main body 100 can be autoclaved, and medical and food manufacturing that requires hygiene management. Can be used safely at the site. Moreover, you may form the housing | casing 10 and / or the cover 50 using resin which added the coloring agent which has absorption in a visible region so that an internal structure cannot be seen.

  An operation unit 17 for accessing a setting unit 32 described later is formed on the side surface of the housing 10. FIG. 3D shows an enlarged view of the operation unit 17. The operation unit 17 is a recess formed with a thin thickness so that the switch of the setting unit 32 disposed in the case 10 can be operated. The sensitivity range changeover switch 32a and sensitivity fine adjustment described later are used. Through holes 17a and 17b through which the knob 32b passes are formed. Further, a waterproof cap 21 is inserted into the operation unit 17 so that waterproofness is ensured during use.

  Further, a cable outlet 18 for passing a cable 60 described later is provided on the side surface of the housing 10. By attaching the waterproof cap 22 through the cable 60 to the cable outlet 18, liquid can be prevented from entering the main body 100 from the outside via the cable outlet 18.

  In the internal space of the main body 100, the circuit unit 30, the four light shielding guides 40, and one end of the cable 60 are accommodated. The cable 60 is connected to the circuit unit 30 and supplies power to the circuit unit and transmits an alarm signal output from the circuit unit to an external device.

  The circuit unit 30 is an electric circuit mounted on two connected printed wiring boards 30a and 30b. FIG. 5 is a block diagram illustrating a schematic configuration of the circuit unit 30. As shown in FIG. 5, the circuit unit 30 includes a control unit 31, a setting unit 32, a light source driving circuit 33, a light source 34, a light receiving element 35, a signal processing circuit 36, an alarm output unit 37, an LED indicator 38, and an external output. A terminal 39 is provided.

  The control unit 31 is connected to the setting unit 32, the light source driving circuit 33, the signal processing circuit 36, and the alarm output unit 37, and controls the operation of the entire circuit unit 30. In addition, the control unit 31 includes a liquid breakage determination circuit 31a that determines the presence or absence of liquid in the translucent tube T based on the output of the signal processing circuit 36 (that is, a signal indicating the amount of light detected by the light receiving element 35). Yes. When the controller 31 determines that the liquid running out determination circuit 31a is running out of liquid (the state where there is no liquid in the translucent tube T), the controller 31 controls the alarm output unit 37 to blink the LED indicator 38, and / or Alternatively, an alarm signal is output to the external output terminal.

  The setting unit 32 is a unit for setting the light receiving sensitivity and an operation mode (also referred to as “determination mode”) to be described later. As shown in FIG. 2, the sensitivity range changeover switch 32a, the sensitivity fine adjustment knob 32b, and An operation mode changeover switch (not shown) is included. The sensitivity range changeover switch 32a is a changeover switch for switching the light receiving sensitivity largely to two setting ranges (high sensitivity range and low sensitivity range) according to the characteristics of the liquid to be detected. The low sensitivity range is used to detect liquids with high transparency, and the high sensitivity range is low transparency such as liquids with strong absorption in the wavelength range of suspensions and light sources (i.e., there is liquid in the tube). Used when detecting liquid). The sensitivity fine adjustment knob 32b is a variable resistor for performing fine adjustment of sensitivity in each sensitivity setting range. The operation mode switch is a dip switch for switching the setting of a plurality of operation modes in which the liquid sensor 1 can operate. Details of each operation mode will be described later.

  A light source 34 is connected to the light source drive circuit 33 and supplies a drive current to the light source 34. The light source 34 generates monitor light by the drive current supplied from the light source drive circuit 33. The light receiving element 35 receives the monitor light that has passed through the translucent tube T substantially straightly, and outputs a current signal corresponding to the amount of received light to the signal processing circuit 36. The signal processing circuit 36 converts the current signal output from the light receiving element 35 into a voltage signal, amplifies it, and outputs it to the control unit 31.

  In the present embodiment, a near-infrared LED light source having a peak emission wavelength of 940 nm is used as the light source 34, but a light source of another type or emission wavelength may be used. For example, a visible light source or a high output LD light source can be used. The emission wavelength and output of the light source 34 can be appropriately selected according to the translucent tube T to be used, the optical characteristics of the liquid to be detected, and the like. In the present embodiment, a silicon photodiode is used as the light receiving element 35, but other types of light receiving elements may be used. As the light receiving element 35, one having sufficient sensitivity to the wavelength of the monitor light generated by the light source 34 is selected.

  As shown in FIG. 4A, a translucent tube T is disposed between the light emitting surface of the light source 34 and the light receiving surface of the light receiving element 35 of each optical system. The light beam of the monitor light emitted from the light source 34 enters the translucent tube T from the side so as to pass through the central axis of the translucent tube T and to be orthogonal to the central axis.

As shown in FIGS. 2 to 5, the circuit unit 30 includes two systems of optical systems including a pair of light sources 34 and light receiving elements 35. Further, as shown in FIG. 4A, the pair of the light source 34 and the light receiving element 35 of each system is arranged so that the light emitting surface and the light receiving surface face each other with a predetermined distance d ₁ (for example, 15 mm). ing. Distance d ₁ of the pair of optical elements is appropriately set according to the outside diameter of the translucent tube T disposed between the elements. In addition, the pair of the light source 34 and the light receiving element 35 of each system is positioned so that the optical axes thereof are exactly coincident with each other. This accurate positioning is realized by the spacer 30c, the light shielding guide 40, and the cover 50 as described later.

Further, as shown in FIG. 3A, the optical axes of the two optical systems (a pair of the light source 34 and the light receiving element 35 arranged to face each other) are predetermined in the length direction of the translucent tube T. Are spaced apart by a distance d ₂ (for example, 20 mm). That is, the liquid sensor 1 of this embodiment is the same as the two points separated by a predetermined distance d ₂ in the longitudinal direction of the translucent tube T, to detect the intensity of the monitor light transmitted through the translucent tube T substantially straightforward .

  Further, as shown in FIG. 2, the two optical systems are arranged so that the irradiation directions of the monitor light (in other words, the directions of the light emitting surface of the light source 34 and the light receiving surface of the light receiving element 35) are opposite to each other. Has been. In this way, by making the irradiation directions of the two adjacent optical systems opposite to each other, the light receiving element does not receive the monitor light of the other systems, and the liquid can be detected more accurately. become.

  Further, as shown in FIG. 2, a spacer 30c is disposed under the package portion of each light receiving element (light source 34 and light receiving element 35) so as to surround the pin. All the spacers 30c have the same height, and are used to accurately position the height of the optical axis from the substrate when each light receiving element is mounted on the substrate.

  The light shielding guide 40 is a member for shielding the optical system from outside light and accurately positioning each optical element with respect to the cover 50, and is provided for each optical element. The light shielding guide 40 is formed of a material that is opaque to light in a wavelength range in which the light receiving element 35 has sensitivity, as in the case 10. The light shielding guide 40 of the present embodiment is formed from a colored resin.

  The light shielding guide 40 is a cap-shaped member having an approximately rectangular parallelepiped outer shape and having an internal space 44 (FIG. 4) opened on the lower surface. The inner space 44 of the light shielding guide 40 is formed so as to accommodate at least the package portion of each optical element and the upper portion of the spacer 30c without play at least for the package portion of the optical element. The light source 34 and the light receiving element 35 mounted on the upper surface of the substrate are covered. Further, two fixing pins for fixing to the substrate are formed at the lower end of the light shielding guide 40. By inserting these fixing pins into corresponding through holes provided in the circuit board 30a, the optical element accommodated in the light shielding guide 40 is accurately positioned on the circuit board 30a (XY plane).

  On the side wall of the light shielding guide 40 facing the light emitting surface or the light receiving surface, a round hole 40h having a diameter substantially the same as the beam diameter of the monitor light is formed at a position where the optical axis passes. The circular hole 40h of the light shielding guide 40 covered by the light source 34 passes only the central portion effective for liquid detection in the beam profile of the monitor light emitted from the light source 34, and does not contribute to liquid detection. Cut part). Such components in the peripheral region of the monitor light not only contribute to the detection of the liquid but also become noise light and cause erroneous detection. Therefore, by confining the components in the peripheral region of the monitor light in the light shielding guide 40 without passing through the round hole 40h, the optical noise is reduced and the occurrence of erroneous detection is suppressed. Further, the light shielding guide 40 placed on the light receiving element 35 allows only the light detected by the light receiving element 35 to pass through the round hole 40h of the light shielding guide 40 and travel substantially parallel to the optical axis of the light receiving element 35. Restrict. As a result, the light received by the light receiving element 35 is substantially only the light directly incident on the light receiving element 35 from the light source 34 of the same optical system, and optical noise such as outside light and scattered light is removed.

  In addition, the three side walls except the front surface (the surface on which the round hole 40h is formed) of the light shielding guide 40 are gently inclined so as to fall inward. These inclined surfaces function as a guide for correctly accommodating the light shielding guide 40 in the space (recessed portion 54) formed inside the cover 50 when the cover 50 is attached to the housing 10.

  In addition to serving as a transparent lid that seals the main body 100 while allowing the monitor light to pass, the cover 50 optically transmits the translucent tube T (directly attached to the translucent tube T). It has a role of positioning with respect to the element (directly the light shielding guide 40). The cover 50 is formed with two protrusions 51 that protrude upward and extend in the X-axis direction, and a recess 52 sandwiched between the two protrusions 51. The translucent tube T is accommodated in the recess 52. The cover 50 is formed with four support walls 53 parallel to the YZ plane for supporting the translucent tube T at a predetermined position so as to communicate the two protruding portions 51. A U-shaped groove 53 a in which the translucent tube T is accommodated is formed in the support wall 53. The diameter of the lower curved surface of the U-shaped groove 53 a is formed to be the same as the maximum diameter of the translucent tube T that is compatible with the liquid sensor 1. In addition, the upper wall surface of the U-shaped groove 53a is a tapered surface in which the groove width increases toward the upper side so that the translucent tube T can be easily dropped into the U-shaped groove 53a.

  A concave portion 54 that accommodates the light shielding guide 40 without play is formed inside the protruding portion 51. As described above, the light shielding guide 40 has one side wall perpendicular to the XY plane in which the round hole 40h is formed, and three side walls that are gently inclined so as to fall inward. Each concave portion 54 is formed with one vertical inner wall surface and three inclined inner wall surfaces corresponding to these side walls of the light shielding guide 40, and the inclined inner wall surface when the main body 100 is assembled is the light shielding guide. 40 is guided to an accurate position with respect to the cover 50 (and thus the translucent tube T).

  Further, a flange 55 protruding outward is formed at a lower portion of the side surface of the cover 50. Support walls 56 extending vertically upward from the flange portion 55 are formed at both ends in the X-axis direction of the cover 50. A U-shaped groove 56 a similar to the U-shaped groove 53 a of the support wall 53 is also formed in the support wall 56. In addition, a connecting wall 57 that extends in the X-axis direction from both ends in the Y-axis direction of the upper portion of the support wall 56 and connects the support wall 56 and each protrusion 51 is provided. Further, a lower gripping portion 58 that connects the bottom of the U-shaped groove 56 a and the bottom of the U-shaped groove 53 a of the support wall 53 closest to the support wall 56 is formed. The upper surface of the lower grip 58 forms one curved surface that is continuous with the bottom surfaces of the U-shaped groove 53a and the U-shaped groove 56a.

  As shown in FIG. 3, a lens portion 59 formed in a lens-like curved surface is provided on the upper surface of one projecting portion 51 located immediately above the LED indicator 38. The display light emitted from the ED indicator 38 is diffused by the lens unit 59, and the viewing angle is widened. The lens part 59 improves the visibility of the LED indicator.

  Next, the structure and function of the attachment 200 will be described. As described above, the attachment 200 shields the liquid detection portion of the translucent tube T from external light, and accurately positions and holds the translucent tube T with respect to the optical system of the main body 100. . For this reason, the attachment is an integral part molded from a resin having light shielding properties and relatively excellent molding accuracy and shape stability. As shown in FIGS. 2 to 4, the attachment 200 includes a semi-cylindrical cover portion 210 that covers the translucent tube T from above, and the cover portion 210 and the translucent tube T at both ends of the cover portion 210 in the X-axis direction. The side wall portion 220 is parallel to the YZ plane and is formed so as to cover the gap. As shown in FIG. 5 (b), the center of the lower end of the side wall 220 is cut out in a U-shape to form an upper grip 222. The bottom of the upper grip 222 is formed in a cylindrical surface having the same diameter as the translucent tube T, so that the translucent tube T can be sandwiched and gripped with the lower grip 58 of the cover 50. ing. In addition, slits 224 extending deeply upward from the lower end of the side wall 220 are formed on both sides of the upper grip 222 in the Y-axis direction. An elongated portion on the outer side in the Y-axis direction of the side wall portion 220 separated by the slit 224 is formed as an elastically deformable leg portion 226 extending in the Z-axis direction. An engaging claw 228 that protrudes outward in the Y-axis direction is formed at the lower end of the leg portion 226.

  As shown in FIGS. 2 and 4C, a protrusion 230 that protrudes downward from the lower surface of the cover part 210 is formed at the center in the X-axis direction of the attachment 200. As shown in FIG. 4C, a U-shaped groove 232 that accommodates the translucent tube T is formed at the lower end of the protrusion 230. The bottom of the groove 232 is formed in a cylindrical surface having the same diameter as the translucent tube T, and holds the translucent tube T in a predetermined position in an extended state.

  In addition, at the center in the X-axis direction of the attachment 200, a recess 250 is formed on the upper surface of the cover portion 210 to accommodate the lock mechanism BL of the binding band B. From both ends of the concave portion 250 in the Y-axis direction, through holes 252 that vertically penetrate the cover portion 210 and the protruding portion 230 extend downward.

  On the lower surface of the cover part 210, four projecting parts 240 that sandwich the translucent tube T with the support wall 53 are formed at positions facing the four support walls 53 provided on the cover 50. ing. As shown in FIG. 4A, a groove 242 formed in a cylindrical surface shape having the same diameter as the translucent tube T is formed at the lower end of the projecting portion 240, and the translucent tube T has a large size. The translucent tube T can be clamped with a wide contact area without applying distortion.

  As shown in FIG. 4A, when the attachment 200 with the translucent tube T attached thereto is attached to the liquid sensor main body 100, the pair of the light source 34 and the light receiving element 35 that are arranged to face each other are common. The translucent tube T is accurately positioned with respect to the liquid sensor main body 100 (specifically, the optical axis of each optical system) so that the optical axis passes through the central axis of the translucent tube T.

  Next, the procedure and mechanism for attaching the translucent tube T to the liquid sensor 1 using the attachment 200 will be described. First, the attachment 200 is attached to the translucent tube T. Specifically, a U-shaped groove-shaped upper gripping part 222 formed on the lower surface of the side wall part 220 provided at both ends of the attachment 200 in the X-axis direction, and a protrusion 230 provided at the center of the attachment 200 in the X-axis direction. The translucent tube T is accommodated in a U-shaped groove 232 formed on the lower surface of the tube.

  Note that the attachment 200 is prepared for each standard size (for example, 3 mm diameter, 6 mm diameter, etc.) of the translucent tube T, and one that matches the outer diameter of the translucent tube T to be used is selected. When the translucent tube T that is completely adapted to the design dimensions of the attachment 200 (specifically, the upper gripping portion 222 and the groove 232) is used under normal conditions, the translucent properties of each U-shaped groove of the attachment 200 are translucent. The attachment 200 is attached to the translucent tube T with a sufficient gripping force simply by inserting the tube T. However, the specification value (standard value and tolerance) of the outer diameter of the translucent tube T varies depending on the manufacturer and type (material, etc.). For example, the standard value of a tube with a nominal diameter of 3 mm is about 2.8 mm. Some of them are about 10% thinner. When such a thin tube is used, a sufficient gripping force may not be obtained. In addition, even if the translucent tube T is perfectly compatible with the design size of the attachment 200 at the standard temperature, the translucent tube T contracts, for example, when the operating temperature is low, so that it conforms to the size of the attachment 200. Sometimes it doesn't work. Further, the gripping force is insufficient even when a large pulling force is applied, for example, when the liquid sensor 1 is hung from the tube. When such a thin tube is used, or when a force for gripping the translucent tube T is insufficient due to a large pulling force, the translucent tube T is attached to the attachment 200 using the binding band B. Tighten to and fix firmly.

  When the translucent tube T is fixed to the attachment 200 with the binding band B, the band Ba of the binding band B is inserted through the hole with the translucent tube T inserted into the upper gripping portion 222 and the groove 232 of the attachment 200. After passing the band Ba through one of the 252 from top to bottom and then through the other through-hole 252 from bottom to top, the band Ba is inserted into the lock mechanism BL and bound, and the remaining band Ba is cut. FIG. 6 is an external view of the liquid sensor 1 showing a state where the translucent tube T is mounted using the binding band B. FIG. FIG. 6A is a top view, and a DD cross-sectional view thereof is FIG. 6B. As shown in FIG. 6, most of the lock mechanism BL of the binding band B is accommodated in the recess 250 of the attachment 200, so that the lock mechanism BL does not protrude greatly outside the attachment 200. The liquid sensor is often installed in a bare state in a narrow space where a staff moves around such as a kitchen. For this reason, the arm of the staff or the like exposed to the lock mechanism BL of the binding band protruding from the casing of the liquid sensor may come into contact, and scratches may occur. The liquid sensor 1 according to the present embodiment can be normally attached to the translucent tube T without using the binding band B. When the binding band B is used, the lock mechanism BL is located in the recess 250 of the attachment 200. Therefore, the user is prevented from coming into contact with the locking mechanism BL of the binding band B and being damaged.

  Next, a procedure and mechanism for attaching the attachment 200 to the liquid sensor main body 100 (specifically, the cover 50) will be described. The attachment 200 attached to the translucent tube T is attached to the cover 50 so that the translucent tube T is accommodated in the concave portion 52 of the cover 50 and the concave portion 52 is covered by the attachment 200. Specifically, with the translucent tube T facing the cover 50 side, the side wall portions 220 formed at both ends of the attachment 200 in the X-axis direction are supported by the support walls 56 formed at both ends of the case 50 in the X-axis direction. The attachment 200 is fixed to the case 50 by being inserted into a space surrounded by the wall 53 and the pair of connecting walls 57. At this time, as shown in FIG. 4B, the engaging claws 228 of the leg portions 226 arranged at the four corners of the attachment 200 engage with the lower end of the connecting wall 57 so that the attachment is not detached from the case 50. become. Since the slit 224 is formed, the leg portion 226 can be elastically deformed in the Y-axis direction. Further, since the interval between the pair of engaging claws 228 is wider than the interval between the inner side surfaces of the connecting wall 57, each of the engaging claws 228 is moved inward in the Y-axis direction by the corresponding connecting wall 57 when the attachment 200 is attached. Pressed. At this time, the leg portion 226 is elastically deformed and bent inward in the Y-axis direction, whereby the distance between the pair of engaging claws 228 is reduced to the distance between the inner side surfaces of the pair of connecting walls 57. When passing between the pair of connecting walls 57, the interval between the pair of engaging claws 228 is restored to the original due to the elastic force, and the engaging claws 228 engage with the connecting walls 57 and the attachment 200 cannot be detached. In addition, by pushing the engagement claw 228 inward in the Y-axis direction, the engagement between the engagement claw 228 and the connecting wall 57 is released, and the attachment 200 can be detached.

  As described above, in the present embodiment, the attachment 200 is prepared in a plurality of sizes corresponding to the size of a general translucent tube T, and the attachment 200 having a size suitable for the translucent tube T to be used. Is selected. The positioning of the translucent tube T is related not only to the matching between the attachment 200 and the translucent tube T but also to the matching with the dimension on the liquid sensor main body 100 (specifically, the cover 50) side. However, since an electric circuit including an optical element is arranged inside the liquid sensor main body 100 and has a waterproof structure, it is safe and quality assurance for the user to remove the cover 50 of the liquid sensor main body 100. Not preferable. Therefore, when the thin translucent tube T is used, the tube adjuster 300 is used so that the central axis of the translucent tube T is accurately arranged on the optical axis.

  FIG. 7 is an exploded view for explaining a state in which the translucent tube T is attached to the liquid sensor 1 using the tube adjuster 300, and FIG. 8 is a perspective view showing an appearance of the tube adjuster 300. In addition, the tube adjuster 300 in this embodiment is a member integrally formed of resin.

  As shown in FIG. 8, the tube adjuster 300 has a shape in which a cylinder is vertically divided, and includes two tube holding portions 310 arranged side by side in the axial direction, and the bottom portions of the two tube holding portions 310. It has the connection part 320 to connect, and the two leg parts 330 arrange | positioned mutually parallel at the lower part of each tube holding part 310. As shown in FIG.

  The cylindrical outer peripheral surface of the tube holding portion 310 is formed in a shape corresponding to the U-shaped groove 53 a formed in the support wall 53 of the cover 50. In addition, the arrangement interval between the two tube holding portions 310 is the same as the arrangement interval between the two support walls 53 adjacent to each other with the optical axis of each optical system interposed therebetween. The two tube holding portions 310 are disposed on the U-shaped grooves 53a of the two support walls 53 adjacent to each other with the optical axis of one optical system interposed therebetween. Further, the outer distance between the two legs 330 arranged in parallel (the distance between the surfaces outside the X-axis direction) is the inner distance between the two support walls 53 adjacent to each other with the optical axis of each optical system interposed therebetween (X-axis direction). The distance between the inner surfaces). Therefore, the two leg portions 330 of the tube adjuster 300 are inserted between the two adjacent support walls 53, and the tube adjuster 300 cannot move in the X-axis direction. Moreover, since the leg part 330 is formed long in the Y-axis direction, the movement of the tube holding part 310 rotating along the U-shaped groove 53a of the support wall 53 is also restricted. That is, the position of the tube adjuster 300 is fixed by the legs 330. After the tube adjuster 300 is attached to the cover 50 in this manner, the liquid sensor can be attached to the translucent tube T by attaching the attachment 200 attached to the translucent tube T by the method described above. it can.

As described above, in the liquid sensor 1 according to the embodiment of the present invention, the translucent tube T is accurately positioned with respect to the optical axis of the optical element by the light shielding guide 40, the cover 50, and the attachment 200. That is, the light shielding guide 40 accurately positions the light source 34 and the light receiving element 35 with respect to the cover 50, and the attachment 200 accurately positions the light transmissive tube T with respect to the cover 50, so that the light transmissive tube T is formed. The light source 34 and the light receiving element 35 are accurately positioned with respect to the optical axis. Therefore, it is possible to accurately detect the liquid in the translucent tube T.

  Further, the guide structure incorporated in the light shielding guide 40, the cover 50, and the attachment 200 allows the positioning to be performed automatically only by assembling the respective members without performing any positioning adjustment work. Therefore, highly accurate assembly can be performed very efficiently.

  Next, the liquid detection process by the circuit unit 30 will be described. The light flux of the monitor light emitted from the light source 34 is irradiated from the side surface of the translucent tube T so as to be orthogonal to the length direction of the translucent tube T and pass through the central axis of the translucent tube T. . When a liquid is present in the translucent tube T, the difference in refractive index between the liquid and the translucent tube T is reduced, and the inner wall of the translucent tube T (interface between the translucent tube T and the liquid) is reduced. The light flux of the monitor light goes straight without being refracted. Therefore, the light beam of the monitor light is transmitted straight through the translucent tube T, is incident on the light receiving element 35 disposed opposite to the light source 34 with the translucent tube T interposed therebetween, and is detected.

  On the other hand, when the inside of the translucent tube T is empty (filled with gas), the difference in refractive index between the gas and the translucent tube T is large. The light beam is greatly refracted or reflected. For this reason, the light beam of the monitor light cannot be transmitted straight through the translucent tube T and is therefore not detected by the light receiving element 35.

  Therefore, in principle, the liquid breakage determination circuit 31a determines that there is liquid in the translucent tube T when the light receiving element 35 detects the monitor light, and the translucent tube does not detect the monitor light. It is determined that there is no liquid in T.

  However, although air bubbles are often present in the translucent tube T, the air bubbles cause refraction and reflection of the monitor light, which causes erroneous detection. Further, even when the translucent tube T is empty, there are often droplets in the translucent tube T. Since the liquid droplets pass through the monitor light in a straight line, it also causes false detection. In order to prevent erroneous detection due to bubbles or droplets, the liquid sensor according to the embodiment of the present invention is provided with a plurality (two in this embodiment) of optical systems.

  Also, a plurality of algorithms for determining whether or not the liquid has run out based on detection results from a plurality of optical systems can be considered. A suitable algorithm may vary depending on the type of liquid used and the application. Therefore, the liquid sensor 1 of the present embodiment is configured so that the user can select a plurality of operation modes (determination algorithms). The operation mode is switched by operating the operation mode switching switch of the setting unit 32.

  Hereinafter, three operation modes mounted on the liquid sensor 1 will be described. Table 1 is a table for explaining three types of operation modes (mode 1 to mode 3) in which the liquid sensor 1 determines that the liquid has run out based on the liquid detection results of the two optical systems. Table 1 compares the detection results of each optical system and the determination results of each mode for 10 typical cases (cases 1 to 10). The ◯ marks in the table indicate that the corresponding optical system has detected a liquid, or that the liquid shortage determination circuit 31a has determined that there is liquid in the tube (no liquid has run out). In addition, the x mark in the table indicates that the corresponding optical system does not detect the liquid, or that the liquid shortage determination circuit 31a has determined that there is no liquid (liquid shortage) in the tube. In the following description, the two optical systems included in the liquid sensor 1 are referred to as an optical system A and an optical system B. In Table 1, the light source 34A and the light receiving element 35A are optical elements constituting the optical system A, and the light source 34B and the light receiving element 35B are optical elements constituting the optical system B.

<Mode 1>
In mode 1, when at least one optical system detects monitor light (that is, detects liquid), it is determined that there is liquid in the translucent tube T, and all optical systems do not detect monitor light. In this case, it is an OR-type operation mode in which it is determined that there is no liquid (liquid running out) in the translucent tube T. As will be described below, mode 1 is an effective operation mode for suppressing erroneous detection due to small bubbles.

  The size of bubbles generated in the translucent tube T is usually about 0.1 mm to several mm. Accordingly, if the interval between the light beams of the two optical systems is set to be narrower than this, there is a possibility that the two optical systems may erroneously detect simultaneously by one bubble. Therefore, in order to prevent erroneous detection due to large bubbles, it is necessary to set the interval between the light beams of the two optical systems to 10 mm or more. When the liquid storage tank approaches the empty position, the liquid level of the liquid storage tank falls to the sampling port of the infusion pipe, and the liquid is taken into the infusion pipe together with the air in the liquid storage tank. For this reason, bubbles with a length of 15 mm or more (more typically 20 mm or more) that are hardly generated when there is a sufficient remaining amount in the liquid storage tank are frequently generated. Therefore, in general applications, when bubbles of 15 mm or more (preferably 20 mm or more) are detected, it is desirable to determine that the liquid has run out. Therefore, in the embodiment of the present invention, the arrangement interval of the plurality of optical systems (monitor light beams) is set to 15 mm or more (preferably 20 mm or more). In the present embodiment, the interval between the light beams of the two optical systems is set to 20 mm. The optimum dimension of the arrangement interval may vary depending on the liquid clay to be used, the inner diameter of the translucent tube T, and the like.

  Next, a specific determination example in mode 1 will be described with reference to Table 1. Cases 1 to 5 in Table 1 are cases where the liquid is filled in the translucent tube T, and cases 6 to 10 are cases where the liquid is empty in the translucent tube T. Each case differs in the presence / absence, position, number or size of bubbles or droplets.

  Case 1 is an example in which there are no bubbles, and since all of the optical systems naturally detect liquid, the liquid breakage determination circuit 31a determines that there is liquid in the translucent tube T. Cases 2 to 5 are cases where bubbles are present in the tube. Case 2 is an example in which bubbles exist in the middle of the two optical systems. Since no bubbles are located on the optical path of any of the optical systems, all the optical systems detect the liquid, and a liquid breakage determination circuit 31a determines that there is liquid. Case 3 is an example in which bubbles are located on the optical path of one optical system (in this case, optical system B). In this case, the optical system B does not detect the liquid, but the optical system A detects the liquid, so that the liquid shortage determination circuit 31a determines that there is liquid. Case 4 is also an example in which bubbles are located on the optical path of one optical system (in this case, optical system A), as in case 3. Also in this case, the optical system A does not detect the liquid, but the optical system B detects the liquid, so that the liquid shortage determination circuit 31a determines that there is liquid. The situation where a relatively small bubble is located on the optical path of one of the optical systems as in the case 3 and the case 4 frequently occurs in a general liquid sensor application. This is the main cause of frequent out-of-liquid alarms based on malfunctions, which has been a problem in liquid sensors having an optical system. In mode 1, malfunction caused by such a situation is prevented, so that occurrence of unnecessary alarms can be greatly reduced. Case 5 is an example in which large bubbles are generated. In this case, all the optical systems do not detect the liquid, and the liquid shortage determination circuit 31a determines that the liquid has run out (no liquid). As described above, when the remaining amount of the liquid supply source decreases, such a large bubble is often generated. Therefore, in any of the cases 1 to 5 related to bubbles, in Mode 1, an appropriate liquid runout determination is made.

  Case 6 is a case where there is no liquid and no liquid droplets in the translucent tube T. Naturally, since all the optical systems do not detect the liquid, the liquid shortage determination circuit 31a determines that the liquid has run out. Case 7 is an example in which a droplet exists in the middle of the two optical systems, and since no droplet is positioned on the optical path of any of the optical systems, all the optical systems do not detect the liquid, The cut determining circuit 31a determines that the liquid has run out. Case 8 is an example in which a droplet is located on the optical path of one optical system (in this case, optical system B). In this case, the optical system A does not detect the liquid, but since the optical system B detects the liquid, the liquid shortage determination circuit 31a erroneously determines that there is liquid. Case 4 is also an example in which a droplet is located on the optical path of one optical system (in this case, optical system A), as in case 3. Also in this case, the optical system A does not detect the liquid, but since the optical system B detects the liquid, the liquid shortage determination circuit 31a erroneously determines that there is liquid. Case 10 is an example in which a droplet is located on the optical path of each optical system. In this case, since all the optical systems detect liquid, the liquid shortage determination circuit 31a erroneously determines that there is liquid. Thus, mode 1 tends to have many misjudgments regarding droplets. However, since the determination of running out of liquid is always made in the process of reaching the states of cases 8 to 9 and an alarm is issued, an erroneous determination regarding droplets is rarely a practical problem in general applications.

<Mode 2>
In mode 2, when all the optical systems detect liquid, it is determined that there is liquid in the translucent tube T, and when there is even one optical system that does not detect liquid, there is liquid in the translucent tube T. In other words, it is an AND type operation mode. As shown in Table 1, in Mode 2, there is a tendency that the frequency of malfunction related to bubbles is high (for example, Case 3 and Case 4). In other words, mode 2 is highly sensitive to bubbles, and can be used as a bubble sensor in applications that require elimination of bubbles, such as in the fine chemical field and the medical field. In addition, mode 2 has a feature that the determination accuracy regarding the droplet is high (for example, case 8 and case 9). Therefore, mode 2 is also suitable for applications where it is necessary to accurately determine that the tube is empty.
<Mode 3>
Mode 3 is an operation mode for determining the presence or absence of liquid based on the detection result of one system of optical system, and emulates a conventional liquid sensor having only one system of optical system. In mode 3 of the present embodiment, the presence or absence of liquid is determined based on the detection result of the optical system A. As shown in Table 1, the determination result of mode 3 is intermediate between mode 1 and mode 2. This mode is effective for applications that require the same degree of determination accuracy for bubbles and droplets. Moreover, it is also suitable when it is necessary to replace a conventional liquid sensor having only one optical system with a new sensor without changing the operating conditions.

  As described above, the liquid sensor 1 of the present embodiment can be used by selecting an operation mode suitable for the application.

  The above is the description of the embodiment of the present invention. The present invention is not limited to the above-described configuration, and various modifications can be made within the scope of the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Liquid sensor 100 ... Main body 10 ... Housing 18 ... Cable outlet 20 ... Packing 22 ... Waterproof cap 24 ... Long screw 30 ... Circuit unit 30a, 30b ... Circuit board 30c ... Spacer 34 ... Light source (LED light source)
36. Light receiving element (photodiode)
38 ... LED indicator 40 ... Shading guide 40h ... Round hole 50 ... Cover 51 ... Projection 52 ... Recess 53 ... Support wall 53a ... U-shaped groove 54 ... Recess 5
55 ... collar part 56 ... support wall 57 ... connecting wall 58 ... lower grip part 59 ... lens part 60 ... cable 200 ... attachment 210 ... cover part 220 ... side wall part 230 ... projection part 240 ... projection part 250 ... recess 252 ... through Hole 300 ... Tube adjuster 310 ... Tube holding part 320 ... Connection part 330 ... Leg part B ... Binding band T ... Translucent tube T

Claims (13)

A liquid sensor for optically detecting a liquid in a translucent tube,
Two optical systems for detecting the presence or absence of liquid in the translucent tube at two locations separated in the length direction of the translucent tube,
The interval between the two locations is longer than the typical length of bubbles appearing in the translucent tube when the liquid supply source is not running out of liquid, and the range of the typical length of bubbles appearing when running out of liquid. It is set so that it may become inside. The liquid sensor characterized by the above-mentioned.   The liquid sensor according to claim 1, wherein the interval is 15 mm or more.   The liquid sensor according to claim 2, wherein the interval is 20 mm or more.   The liquid center according to claim 2, wherein the interval is 20 mm.   The liquid sensor according to claim 2, wherein the interval is 15 mm. When at least one of the two optical systems detects liquid, it is determined that there is liquid,
6. The liquid sensor according to claim 1, wherein when both of the two optical systems do not detect a liquid, it is determined that there is no liquid.   The light-transmitting tube is provided with three or more optical systems for detecting the presence or absence of liquid in each of the light-transmitting tubes at a plurality of three or more locations separated in the length direction. The liquid sensor according to any one of claims 1 to 6. Each of the two optical systems includes a light source and a light receiving element,
The luminous flux emitted from the light source is incident on the translucent tube from the side surface perpendicular to the central axis of the translucent tube,
In the place where the light beam is incident,
When there is liquid in the translucent tube, the light beam passes straight through the translucent tube and is detected by the light receiving element,
8. The liquid crystal according to claim 1, wherein when there is no liquid in the translucent tube, the light beam is refracted or reflected by the inner wall of the translucent tube and is not detected by the light receiving element. The liquid sensor according to any one of the above.   The liquid sensor according to claim 8, wherein the light source and the light receiving element of the optical system are disposed so that the light emitting surface and the light receiving surface face each other through the light transmitting tube.   The liquid sensor according to claim 8, wherein the light receiving elements of the two optical systems are arranged with light receiving surfaces opposite to each other. The liquid sensor is
A body containing the light source and the light receiving element;
And covering a part of the translucent tube including the two places to shield from external light, and an attachment for positioning and attaching the translucent tube to the main body,
The main body includes a light shielding member that covers each of the light source and the light receiving element and shields it from external light,
The liquid sensor according to claim 8, wherein an opening for allowing the light beam to pass through is formed in the light shielding member. When both of the two optical systems detect liquid, it is determined that there is liquid,
12. The liquid sensor according to claim 1, wherein when one of the two optical systems does not detect the liquid, it is determined that there is no liquid. A first determination mode for determining the presence or absence of liquid according to the algorithm according to claim 6;
A plurality of determination modes including a second determination mode for determining the presence or absence of a liquid according to the algorithm according to claim 12 can be switched.
The liquid sensor according to claim 12, which directly or indirectly cites claim 6.

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