Refractive index formula concentration sensor

Abstract

To detect an accurate concentration even if there is an attached dirt in a liquid.SOLUTION: A refractive-index concentration sensor includes: a diffusion plate 114 for diffusing light emitted from a light source 102; and a prism 104 for receiving light which transmits through the diffusion plate 114 by a first surface, reflecting the light by a second surface in contact with a measurement target liquid, and drawing the reflected light out by a third surface. The light source 102, the diffusion plate 114, the light reception lens 122, and the imaging element 106 are contained in a holder 200 which presses the prism 104 from the inside to the outside.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] When the concentration of a fluid changes, its refractive index also changes. The present invention relates to a refractive-index type concentration sensor that utilizes this characteristic.

Background Art

[0002] The inventors of the present invention came up with the present invention in the process of optimizing an ultrasonic flow rate detection device including an ultrasonic flow switch, a concentration sensor, and a temperature sensor for the management of the coolant of a machine tool.

[0003] For the sake of explanation, first, the ultrasonic flow switch will be described. In a field where it is sufficient to detect whether a fluid is flowing through a pipe at a flow rate equal to or higher than a certain value, in other words, in a field where the exact flow rate value of the fluid flowing through the pipe is not required, an ultrasonic flow switch that outputs an ON / OFF signal is used (Patent Document 1). Patent Document 1 also discloses a clamp-on ultrasonic flow switch. The clamp-on ultrasonic flow switch is installed retrofittably at an appropriate location on the outer peripheral surface of the pipe by incorporating the elements included therein into a unit.

[0004] Next, a conventional refractive-index type concentration sensor will be described. Patent Document 2 discloses a refractive-index type concentration sensor. With reference to FIG. 2 of Patent Document 2, the structure of the refractive-index type concentration sensor 2 disclosed in Patent Document 2 will be described below. The reference signs used in this description are the reference signs described in Patent Document 2. The refractive-index type concentration sensor 2 includes a right-angled prism 22. A light projecting unit 23 is arranged on one inclined surface 22c side of the right-angled prism 22. The measurement object is positioned in contact with the bottom surface 22a of the right-angled prism 22. A light receiving unit 24 is arranged on the other inclined surface 22d side of the right-angled prism 22.

[0005] The light projecting unit 23 includes a plurality of arranged LEDs 25 and a diffusion plate 26 disposed between the plurality of LEDs 25 and the prism 22. On the other hand, the light receiving unit is composed of a lens 27 and an imaging device (CCD) 28. That is, the refractive index type concentration sensor 2 of Patent Document 2 is characterized in that an array light source is adopted as the light source of the light projecting unit, and the light emitted by this array light source is diffused by a diffusion plate and applied to the prism.

[0006] Patent Document 3 discloses another refractive index type concentration sensor. Referring to FIG. 1 of Patent Document 3, the structure of the refractive index type concentration sensor 10 disclosed in Patent Document 3 will be described below. The reference signs used in this description are the reference signs described in Patent Document 3. In the refractive index type concentration sensor 10, a light projecting unit is disposed on the first surface 20 side of the prism 16, and the liquid to be measured is positioned in contact with the second surface 18 of the prism 16. A light receiving unit is disposed on the third surface 22 side.

[0007] The light projecting unit includes a light source 24 and a condenser lens 26 that condenses the light from the light source 24 onto the first surface 20. On the other hand, the light receiving unit preferably includes a polarizing plate 30 installed on the third surface 22. The polarizing plate 30 selectively allows only S-polarized light vibrating in a direction perpendicular to the refractive index measurement surface to pass through. In other words, the polarizing plate 30 is provided with a function of blocking the P-polarized light of external light. The light receiving unit also includes an imaging device 28 and an objective lens 32 disposed between the polarizing plate 30 and the imaging device 28. An arithmetic means for calculating the critical angle and refractive index of the liquid to be measured from the light quantity distribution curve is connected to the imaging device 28.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] Conventional refractive index formula concentration sensors (Patent Document 2) employ a combination of an array light source and a diffuser plate in order to uniformly apply light to the inclined surface on the light projection side of a right-angled prism. However, an array light source is an aggregate of a plurality of LEDs, and it includes manufacturing variations for each LED. Therefore, when the array light source is regarded as a surface light source, it is non-uniform locally, and even if this locally non-uniform light is applied to the light projection side inclined surface of the right-angled prism through the diffuser plate, it is impossible to ensure a high degree of uniformity. This means that unevenness occurs in the amount of light received by the image sensor (CCD), which is related to the accuracy of concentration detection.

[0010] An object of the present invention is A coolant containing a water-soluble cutting oil agent to provide a refractive index formula concentration sensor capable of performing highly accurate concentration detection even when dirt adheres to the inside.

Means for Solving the Problems

[0011] According to the present invention, the above technical problem is a refractive index formula concentration sensor for measuring the concentration of a coolant containing a water-soluble cutting oil agent, a light source, a light projection lens that converts the light emitted from the light source into substantially parallel light, a diffuser plate that diffuses the substantially parallel light generated by passing through the light projection lens constituted by and converts it into a surface light source having a plurality of angular components, before a prism having a first surface that receives light from the surface light source, a second surface that contacts the coolant containing the water-soluble cutting oil agent to be measured and reflects according to the refractive index of the measurement object, and a third surface that extracts the reflected light, a light receiving lens that receives the reflected light received by the third surface of the prism, an image sensor that receives the reflected light through the light receiving lens and acquires a light quantity distribution corresponding to the reflected light, A circuit board for calculating the concentration of the coolant based on the position of the bright and dark lines caused by the critical angle determined based on the light quantity distribution acquired by the imaging device, and the correspondence relationship between the refractive index and the concentration. The prism the prism with the second surface exposed A holder for pressing the prism from the inside to the outside. The light source the projection lens The diffusion plate, the light receiving lens, the imaging device, the substrate 、 The holder 、 The prism to accommodate It is achieved by providing a refractive index type concentration sensor having a housing that houses the above.

[0012] According to the present invention, A coolant containing a water-soluble cutting oil agent is a measurement target, The prism is pressed from the inside to the outside of the housing, and the detection surface of the prism is exposed from the housing in a state where the adhesion between the housing and the prism is enhanced. Instead of attaching the prism from the outside of the housing, attaching it from the inside enhances the waterproof property. By making the surfaces flush, it becomes more difficult for dirt to adhere.

[0013] The present invention also features irradiating a diffusion plate after converting light from a light source into substantially parallel light (collimated light) by a projection lens. The light projecting lens included in the present invention is typically composed of a collimator lens. The light that has passed through the diffusion plate becomes diffused light starting from the diffusion plate, and this diffused light does not have specific angular components. In other words, at each point of the diffusion plate, it is converted into light having a plurality of angular components. As a result, the region included in the diffusion plate, that is, the region irradiated with substantially parallel light through the light projecting lens, can form a uniform surface light source. Thereby A coolant containing a water-soluble cutting oil agent Even if dirt adheres inside, highly accurate concentration detection can be performed.

[0014] The operational effects of the present invention and other objects of the present invention will become clear from the detailed description of the following embodiments.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Mode for Carrying Out the Invention

Examples

[0016] Before explaining the refractive index formula concentration sensor of the embodiment, an ultrasonic flow rate detection device optimized for the management of the coolant of a machine tool will be explained. The ultrasonic flow rate detection device is composed of an ultrasonic flow switch, a concentration sensor, and a temperature sensor. As the ultrasonic flow switch, an integrated clamp-on ultrasonic flow switch with a display function is adopted.

[0017] In a machine tool, a water-soluble cutting oil diluted with water is used. The diluted solution of the water-soluble cutting oil is called "coolant". The amount of the active ingredient in the coolant is small, and it is essential to maintain the concentration of the coolant at an appropriate value in order to exert a lubricating action with this trace component, suppress the corruption of the coolant, suppress the generation of rust, and suppress the deterioration of cutting performance. If the concentration is lower than the recommended value, the processing performance of the machine tool will deteriorate. The operator of the machine tool is learning proper management of the coolant as a skill for improving production quality, reducing running costs, and improving work efficiency. For the operator, proper management of the coolant, especially concentration management, is important for improving the production quality of the machine tool, reducing running costs, and improving work efficiency.

[0018] Referring to FIG. 1, reference numeral 2 indicates a coolant storage tank. The coolant storage tank 2 stores a water-soluble cutting oil diluted with water, that is, coolant. The coolant in the coolant storage tank 2 is supplied to a machine tool (not shown) through a pipe 4.

[0019] A clamp-on ultrasonic flow switch 6 is detachably fixed to the pipe 4 by retrofitting. A concentration sensor 8 with a detection part inserted into, for example, the coolant storage tank 2 is connected to the clamp-on ultrasonic flow switch 6, and a temperature sensor 10 installed at, for example, a connection part of the pipe 4 is also connected. The clamp-on ultrasonic flow switch 6 has a display 64 to be described later, and these elements constitute an ultrasonic flow rate detection device 12.

[0020] FIG. 2 is a diagram for explaining a specific example of the clamp-on ultrasonic flow switch 6. The clamp-on ultrasonic flow switch 6 is composed of three members: a mounting base member 60, a measurement head member 62, and a display 64. The mounting base member 60 can be retrofitted and detachably installed at an appropriate location on the pipe 4. The measurement head member 62 includes first and second ultrasonic elements 66, 68 that constitute a flow detection unit (FIG. 3). The measurement head member 62 is detachably assembled to the above-mentioned mounting base member 60, and the mounting base member 60 maintains the measurement head member 62 in a state of being in pressure contact with the pipe 4.

[0021] The display 64 is assembled to the measurement head member 62. In FIG. 2, (I) is a front view of the display 64, and (II) is a rear view of the display 64. The concentration sensor 8 and the temperature sensor 10 are connected to the display 64. The detected values detected by the concentration sensor 8 and the temperature sensor 10 are displayed on the display 64 as the actual detected numerical values without being processed such as by calculation.

[0022] The clamp-on ultrasonic flow switch 6 is most preferably composed of an integrated clamp-on ultrasonic flow switch (FIG. 3). In the measurement head member 62, it is preferable that the first ultrasonic element 66 and the second ultrasonic element 68 are integrally held by a single element holding portion 70.

[0023] Referring to FIG. 3, the measurement head member 62 incorporates first and second ultrasonic elements 66, 68 for transmitting and receiving ultrasonic waves, and the relative positions of the first and second ultrasonic elements 66, 68 are fixed by the element holding portion 70. The first and second ultrasonic elements 66, 68 are typically composed of piezoelectric elements. The first and second ultrasonic elements 66, 68 are positioned by the element holding portion 70 so as to be spaced apart in the axial direction of the pipe on the generatrix of the pipe 4. The integrated clamp-on ultrasonic flow switch 6 is a so-called V-arrangement method or reflection arrangement method when specified from the viewpoint of the time difference operation mode measured under the principle of the "propagation time difference" method described later.

[0024] Adjacent to the first ultrasonic element 66 included in the measurement head member 62, a first wedge member 162 as the first ultrasonic transmission part 16 is included, and adjacent to the second ultrasonic element 68, a second wedge member 182 as the second ultrasonic transmission part 18 is included. The first wedge member 162 is incorporated into the element holding part 70 and has a first element coupling surface 162a that supports the first ultrasonic element 66 so as to be acoustically coupled to the first ultrasonic element 66, and the first ultrasonic element 66 is installed on this first element coupling surface 162a. The second wedge member 182 is incorporated into the element holding part 70 and has a second element coupling surface 182a that supports the second ultrasonic element 68 so as to be acoustically coupled to the second ultrasonic element 68, and the second ultrasonic element 68 is installed on this second element coupling surface 182a.

[0025] Further, the measurement head member 62 preferably includes first and second couplants 164 and 184 adjacent to the first and second wedge members 162 and 182, respectively. The first and second couplants 164 and 184 constitute a part of the first and second ultrasonic transmission parts 16 and 18, and form a pipe coupling surface that is acoustically coupled to the pipe 4 in the element holding part 70.

[0026] The measurement head member 62 has a circuit board 186 that controls the transmission and reception of the first and second ultrasonic elements 66 and 68 and calculates detection data. As described above, the display 64 is detachably installed on the measurement head member 62. The display 64 includes a display part 64a. The display 64 receives the flow rate obtained by the measurement head member 62 and displays it on the display part 64a.

[0027] The measurement head member 62 includes a time difference measurement operation mode in which the first and second ultrasonic elements 66 and 68 cooperate to perform flow rate measurement in the "propagation time difference" method, and a Doppler measurement operation mode in which the first ultrasonic element 66 operates alone to perform flow rate measurement in the "pulse Doppler" method, and is automatically selected according to the user's selection or, for example, the amount of bubbles in the fluid. For example, it operates alternately between the time difference measurement operation mode and the Doppler measurement operation mode. When there are many bubbles, the Doppler measurement operation mode is automatically set, while when there are few bubbles, the time difference measurement operation mode is automatically set.

[0028] In FIG. 3, the arrow of the solid line RL means that the first and second ultrasonic elements 66 and 68 cooperate to measure the flow rate under the principle of the "propagation time difference" method. On the other hand, the arrow of the dashed line DL means that the first ultrasonic element 66 operates alone to measure the flow rate under the principle of the "pulse Doppler" method.

[0029] Regarding the concentration sensor 8 described above with reference to FIG. 1, two types of refractive index type concentration sensors are prepared. One is a plug-in type, and the concentration sensor 8 illustrated exemplarily in FIG. 1 is a plug-in type. The other is a water-through type. When it is necessary to distinguish between the plug-in type and the water-through type, the plug-in type concentration sensor is labeled with reference numeral 8A, and the water-through type concentration sensor is labeled with reference numeral 8B.

[0030] FIG. 4 is a perspective view of the plug-in type concentration sensor 8A. The plug-in type concentration sensor 8A has a rod-like shape by a housing, and as described with reference to FIG. 1, it is used in a state where the detection unit 8A-1 is inserted into the liquid to be measured in the tank 2 with the detection unit 8A-1 facing downward. The housing of the plug-in type concentration sensor 8A is preferably made of metal. The reference numeral 8A-2 in FIG. 4 indicates an indicator light. The plug-in type concentration sensor 8A has an elongated rod-like shape, with the detection unit 8A-1 disposed at one end in the longitudinal direction and the indicator light 8A-2 provided at the other end. The indicator light 8A-2 is turned on or off when the detected concentration exceeds the threshold value set for the plug-in type concentration sensor 8A. The indicator light 8A-2 disposed on the side opposite to the detection unit 8A-1 in the longitudinal direction can be visually recognized all around, and during the operation of the plug-in type concentration sensor 8A, it is located above the liquid level of the liquid, so it can be easily visually recognized.

[0031] More specifically regarding the indicator light 8A-2, the indicator light 8A-2 that emits light all around has two-color LEDs (green, red) of red and green, and as a lighting pattern, it realizes lighting with amber-colored light in which both green and red are lit. Depending on the state of the concentration sensor, which color LED is turned on, off, or blinked is changed. Among the indicator lights 8A-2, for example, the green LED and the red LED turn on the green LED when the concentration is within a predetermined range and turn on the red LED when it is outside the predetermined range. When the tank is dry, it blinks red. Among the indicator lights 8A-2, for example, the amber lighting and blinking inform the user that it is time for maintenance. Also, when there is dirt on the detection window, by making it blink amber, the user can be made to recognize that it is a state different from the states represented by green and red.

[0032] Also, the indicator light 8A-2 is disposed at a portion close to the housing cable of the plug-in type concentration sensor 8A, most preferably at the end, and has a frustum of a cone shape. For this reason, it is easy to visually recognize from all 360 degrees around, and since it is disposed above the liquid level of the tank 2, it is also easy to visually recognize the indicator light 8A-2 even from above the tank 2.

[0033] FIG. 5 and FIG. 6 are explanatory diagrams showing the installation of the plug-in type concentration sensor 8A using the jig 80, and show the process of inserting the detection unit 8A-1 of the plug-in type concentration sensor 8A into the tank 2. FIG. 5 is a side view, and the jig of the plug-in type concentration sensor 8A is in an unlocked state. FIG. 6 is a perspective view corresponding to FIG. 5. FIGS. 7 and 8 show a state where the plug-in type concentration sensor 8A is fixed to, for example, the tank 2 using the jig 80. FIG. 7 is a side view, and the jig of the plug-in type concentration sensor 8A is in a locked state. FIG. 8 is a perspective view corresponding to FIG. 7.

[0034] The jig 80 includes, for example, a pedestal plate 82 installed at the opening of the tank 2, and also includes a lever-type fixture 84 detachably installed on the plug-in type concentration sensor 8A. This fixture 84 is detachably fixed to the concentration sensor 8A by bolts 88.

[0035] Referring to FIGS. 5 and 6, when inserting or removing the detection unit 8A-1 of the plug-in type concentration sensor 8A into / from the measurement target liquid S in the tank 2, the lever-type fixture 84 is in an unlocked state. Referring to FIGS. 7 and 8, the plug-in type concentration sensor 8A is fixed to the tank 2 by the user pushing down the lever-type fixture 84 to lock it. The detection unit 8A-1 of the plug-in type concentration sensor 8A has a detection window 86 (FIG. 8), and the concentration of the measurement target liquid in the tank 2 is detected through this detection window 86. As can be seen from FIGS. 4 to 8, the detection unit 8A-1 of the plug-in type concentration sensor 8A is held in a horizontally oriented posture. Thereby, the detection window 86 of the detection unit 8A-1 is composed of a surface extending in the vertical direction.

[0036] Even when installing the jig 80, since it is fixed at an intermediate portion between the detection unit 8A-1 side and the indicator light 8A-2, that is, closer to the detection unit 8A-1 than the indicator light 8A-2, on the housing of the plug-in type concentration sensor 8A, the indicator light 8A-2 can be visually recognized from the outside.

[0037] Figs. 9 and 10 show the water-flow type concentration sensor 8B. Fig. 9 is a side view, and Fig. 10 is a perspective view. Figs. 11 to 13 show the water-flow type concentration sensor 8B incorporated in the pipe 4. Fig. 11 is a perspective view, Fig. 12 is a plan view, and Fig. 13 is a side view.

[0038] The water-flow type concentration sensor 8B is installed in the pipe 4 with the detection part 8B-1 facing the inside of the pipe 4. The reference numeral 90 in Fig. 10 indicates the detection window of the water-flow type concentration sensor 8B. The detection window 90 is located in the detection part 8B-1, and the concentration of the liquid to be measured flowing through the pipe 4 is detected through this detection window 90. The reference numeral 8B-2 in Fig. 9 indicates an indicator light. The indicator light 8B-2 included in the water-flow type concentration sensor 8B is substantially the same as the indicator light 8A-2 of the above-described plug-in type concentration sensor 8A in terms of structure and function. For example, the indicator light 8B-2 included in the water-flow type concentration sensor 8B can emit light in all directions of 360 degrees around, and its lighting or flashing can be visually recognized throughout the entire circumference, similar to the indicator light 8A-2 of the above-described plug-in type concentration sensor 8A. Therefore, a detailed description of the indicator light 8B-2 included in the water-flow type concentration sensor 8B is omitted.

[0039] In the water-flow type concentration sensor 8B, the indicator light 8B-2 is provided at the cable connector part of the water-flow type concentration sensor 8B, that is, at the terminal, and is arranged on the detection part 8B-1 side of this connector part, that is, the terminal, and the shape of the indicator light 8B-2 is a frustum of a cone shape. The housing of the water-flow type concentration sensor 8B is preferably made of metal, similar to the housing of the plug-in type concentration sensor 8A.

[0040] FIG. 14 is a diagram for explaining the structure of the detection unit 8A-1 of the plug-in type concentration sensor 8A. As shown in FIG. 14, an LED light source 102, a monitor PD103 for light quantity control, a projection lens 112, and a diffusion plate 114, which will be described later, are modularized and attached to a holder 200 as a light projection module and incorporated. Similarly, an imaging element 106 and a light receiving lens 122 are also modularized and attached to the holder 200 as a light receiving module and incorporated. A detection window 86 is provided in the metal housing 81 of the plug-in type concentration sensor 8A. The light projection module including the elements 102, 112, 114, the light receiving module including the elements 106, 122, and the main board CB(m) are assembled to the pressing member 200. After that, the pressing member, that is, the holder 200 on which each element is mounted, is installed in relation to the prism 130, and then the whole is pressed against the metal housing 81 and fixed. At that time, a rubber first packing 123 as a water stop member is interposed between a step portion extending in the circumferential direction around the prism 130, that is, a circumferential flange, and the metal housing 81. By pressing and fixing against the metal housing 81, the first packing 123 is crushed to prevent water from entering from the outside to the inside of the housing 81. Between the step portion extending around the prism 130, that is, the circumferential flange, and the surface of the metal housing 81, the metal housing 81 is partially thinned to form a space for accommodating the first packing 123. Thus, as will be described later, a flush detection window 86 is realized. Further, in the detection unit 8A-1, a temperature sensor (temperature measurement circuit) 40 is provided on the tip side of the prism 130. In the portion where the temperature measurement circuit 40 is provided, the metal housing 81 is provided thinner than other portions. The prism 130 is pressed, and is thinner than the thinned portion.

[0041] Between the above-described first housing 81 and a separate second housing 83, a second packing 124 as a water-stop member is also interposed. By pressing the first housing 81 and the second housing 83 to crush the second packing 124, water intrusion from the interface portion, i.e., the mating surface, of the first housing 81 and the second housing 83 into the inside of the plug-in type concentration sensor 8a is prevented. After integrating the first and second housings 81 and 83, the assembly is inserted into, fitted to, and screwed to a third housing 85 to be fixed, thereby preventing water intrusion from the interface, i.e., the mating surface, between the second housing 83 and the third housing 85.

[0042] FIG. 15 is a diagram for explaining the structure of a detection unit 8B-1 of a water-passing type concentration sensor 8B. As shown in FIG. 15, a light-emitting module (102, 112), a light-receiving module (106, 122), and a main board CB(m) are assembled to a pressing member 205. Then, the pressing member 205 on which each element is mounted is attached to a prism 140, and the whole is pressed against and fixed to a metal housing 87 having a detection window 90 of 8B. At this time, a rubber packing 125 as a water-stop member is interposed between the peripheral flange of the prism 140 and the metal housing 87. By crushing this packing 125, water intrusion from the outside of the housing 87 into the inside of the water-passing type concentration sensor 8B is prevented. Between the stepped portion extending around the prism 140, i.e., the peripheral flange, and the surface of the metal housing 87, the metal housing 81 is partially thinned to form a space for accommodating the packing 125. Thereby, as will be described later, a flush detection window 90 is realized. Further, a temperature sensor (temperature measurement circuit) 40 is provided on the tip side of the prism 140 in the detection unit 8B-1. In the portion where the temperature measurement circuit 40 is provided, the metal housing 87 is provided thinner than other portions.

[0043] The insertion type detection unit 8A-1 and the water flow type detection unit 8B-1 basically have the same structure, and this basic structure is shown in FIG. 16. Referring to FIG. 16, the basic structure common to the insertion type and the water flow type will be described. The basic structure common to the insertion type concentration sensor 8A and the water flow type concentration sensor 8B includes a light source 102, a prism 104, and an imaging element 106. The light source 102 is composed of a single LED light source. As an example, a single amber LED with a central wavelength of about 589 nm is used. The LED light source 102 constitutes a part of the light projecting unit 110, and the light projecting unit 110 irradiates light on the first surface 104a of the prism 104. The light projecting unit 110 located on the input side of the prism 104 includes at least the LED light source 102 and a diffusion plate 114. The light projecting unit 110 includes a light projecting lens 112 that receives the light from the LED light source 102 and preferably makes it into substantially parallel light. The light projecting lens 112 is typically composed of a collimator lens. The light projecting unit 110 further includes a diffusion plate 114 that diffuses the substantially parallel light generated by passing through the light projecting lens 112. The light passing through the diffusion plate 114 becomes diffused light starting from the diffusion plate 114, and this diffused light does not have a specific angular component. That is, the diffusion plate 114 converts the light into light having a plurality of angular components at each point of the diffusion plate 114. Thereby, the diffusion plate 114 constitutes a uniform surface light source and irradiates the first surface 104a of the prism 104. Referring to FIGS. 14 and 15, adjacent to the LED light source 102, a monitor PD103 for monitoring the light emission amount of the LED light source 102 is provided (see FIG. 19). By monitoring the light received by this monitor PD103, the control unit controls the light emission amount of the LED light source 102 so that the light emission amount from the LED light source 102 becomes constant.

[0044] When an amber LED light source with a central wavelength of about 589 nm is used, its temperature characteristics are not as good as those of other LEDs. Regardless of the ambient temperature including the temperature of the liquid, in order to make the light emission amount constant, the light emission amount of the LED is observed, and the current amount supplied to the LED light source is controlled according to the light emission amount. The current amount may be increased or decreased, or the duty ratio of the LED that is pulsed may be adjusted so that the light emission amount becomes constant.

[0045] The second surface 104b of the prism 104 is positioned facing the liquid to be measured through the detection window 86 or 90 and comes into contact with the liquid to be measured. The light diffused by the diffusion plate 114 enters the prism 104 through the first surface 104a, is reflected by the second surface 104b in contact with the liquid to be measured, and this reflected light exits the prism 104 to the outside through the third surface 104c on the light receiving unit 120 side. The light receiving unit 120 is composed of a light receiving lens 122 and an imaging element 106. The reflected light exiting the prism 104 through the third surface 104c is condensed by the light receiving lens 122, and the light condensed by the light receiving lens 122 is input into the imaging element 106. The imaging element 106 is typically composed of a one-dimensional CMOS sensor. The total reflection light at the interface between the prism 104 and the target liquid is condensed onto the imaging element 106 by the light receiving lens 122 to obtain the light quantity distribution. The change in the refractive index due to the concentration of the liquid is measured as the change in the condensation position on the imaging element 106. The change in concentration and the change in refractive index are in a proportional relationship, and by measuring the change in refractive index, the concentration of the target liquid can be measured.

[0046] In the imaging element 106, instead of always being in the light receiving state, a set of on and off of imaging is periodically performed, where imaging is performed multiple times at short intervals and then turned off for a long time thereafter, thereby suppressing the heat generation from the imaging element 106. This suppresses positional displacement of the substrate on which the imaging element 106 is mounted due to heat generation from the imaging element 106. In a refractive index type concentration sensor, since the concentration is measured from the light quantity distribution of the imaging element 106, there is a problem in principle that even a slight positional displacement of the substrate directly affects the measurement accuracy of the concentration. In contrast, in a temperature sensor that requires constant measurement, in order not to reduce the measurement accuracy of the concentration, a set of periodically repeating on and off is periodically performed to suppress the heat generation on the imaging element 106 side.

[0047] FIG. 17 and FIG. 18 are diagrams for explaining that the refractive index at the second surface 104b in contact with the liquid S to be measured changes depending on the concentration of the liquid S to be measured. Referring to FIG. 17, the ratio between the incident angle θ1 with respect to the second surface 104b and the exit angle θ2 of the reflected light at the second surface 104b is the refractive index, and this refractive index changes depending on the concentration of the liquid S to be measured. This change can be known by the displacement of the portion focused on the imaging element 106.

[0048] Returning to FIGS. 14 and 15, FIG. 14 shows the specific structure of the detection unit 8A-1 of the insertion type concentration sensor 8A. FIG. 15 shows the specific structure of the detection unit 8B-1 of the water flow type concentration sensor 8B. In the specific structure, the difference between the insertion type concentration sensor 8A and the water flow type concentration sensor 8B is related to the material of the prism 104. In the insertion type shown in FIG. 14, a quartz prism 130 is adopted as the prism 104. In the water flow type shown in FIG. 15, a sapphire prism 140 is adopted as the prism 104. The reference sign CB(m) shown in FIGS. 14 and 15 indicates the main substrate.

[0049] In the water flow type concentration sensor 8B, a polarizing plate 128 (FIG. 15) is interposed between the first surface 104a of the sapphire prism 140 and the diffusion plate 114. The sapphire prism 140 has the characteristic that its refractive index changes depending on the polarization direction and is not stable. By adjusting the direction of polarization with the polarizing plate 128, the refractive index can be stably detected. The polarizing plate 128 is arranged behind the diffusion plate 114 and selectively transmits only P-polarized light. This is to obtain a waveform having a steep slope in the received light waveform shown in FIG. 20.

[0050] In the prism 104, when comparing the sapphire prism and the quartz prism, the sapphire prism has the property that oil easily adheres to its surface (the contact angle in water is about 10°), while the quartz prism has the property that oil hardly adheres to its surface (the contact angle in water is about 90°). In the insertion type concentration sensor 8A (FIG. 14) that employs the quartz prism 130 as the prism 104, preferably, the second surface 104b in contact with the liquid S to be measured is polished and subjected to a hydrophilic coating. By polishing and applying the hydrophilic coating, it becomes difficult for oil to adhere to the second surface 104b (the contact angle in water becomes 135°). Thereby, by adopting the quartz prism 130, it is possible to provide the quartz prism 130 with resistance to the adhesion of dirt with respect to the second surface 104b even when used in a harsh contamination environment.

[0051] Also, as can be clearly seen from FIGS. 14 and 15, the detection window 86 of the insertion type concentration sensor 8A and the detection window 90 of the water flow type concentration sensor 8B are flush with the second surface 104b of the prism 104. Thereby, for example, when the second surface 104b of the prism 104 is positioned lower than the detection windows 86 and 90, recesses are formed in the detection windows 86 and 90 by the second surface 104b, and oil and bubbles contained in the liquid S to be measured tend to remain in these recesses. On the other hand, the detection windows 86 and 90 of the insertion type concentration sensor 8A (FIG. 14) and the water flow type concentration sensor 8B (FIG. 15) of the embodiment are both given a flush shape so as not to form a recess between the housing and the second surface 104b. Therefore, the presence of the detection windows 86 and 90 does not create a recess between them and the second surface 104b, and the occurrence of a phenomenon where oil and bubbles tend to remain here can be prevented. This contributes to improving the accuracy of measuring the concentration of the liquid S to be measured. Also, as can be seen from FIGS. 6 and 8, the detection window 86 of the insertion type concentration sensor 8A is formed on the vertical surface of the detection unit 8A-1 and has a vertically long shape. Thereby, it is possible to effectively prevent oil and bubbles from adhering to the detection window 86.

[0052] In the insertion type concentration sensor 8A of FIG. 14, the entire portion shown in FIG. 14 is placed in a fluid and is permanently installed in an environment surrounded by liquid. Therefore, the overall waterproof structure is maintained in the portion as described above.

[0053] In the water flow type concentration sensor 8B of FIG. 15, as shown in FIG. 13, only the vicinity of the prism 140 is the portion that is always in contact with the liquid S, and among the portions shown in FIG. 15, the other portions are not always in contact with the liquid. Since it is only necessary to provide waterproofing from the surrounding liquid, waterproofing is performed centering on the liquid contact surface of the prism 140.

[0054] In the basic structure common to the insertion type concentration sensor 8A and the water flow type concentration sensor 8B described above with reference to FIG. 16, it includes a light projecting lens 112 and a diffusion plate 114 that receive the light from the LED light source 102 and make it into substantially parallel light. The diffusion plate 114 constitutes a virtual surface light source. If this were configured with a point light source, contamination and uneven oil film on the second surface 104b in contact with the liquid S to be measured through the detection windows 86 and 90 would affect the measurement accuracy. On the other hand, in the insertion type concentration sensor 8A and the water flow type concentration sensor 8B of the embodiment, by the combination of the light projecting lens 112 that generates substantially parallel light and the diffusion plate 114 that diffuses the substantially parallel light from the light projecting lens 112, a surface light source is created that is converted into light having a plurality of angular components at each point of the diffusion plate 114. With this surface light source, the influence of uneven oil film on the second surface 104b in contact with the liquid S to be measured can be averaged. Also, even if bubbles adhere locally to the second surface 104b, stable concentration measurement becomes possible.

[0055] When the absolute value of the amount of light received by the imaging device 106 decreases, it can be assumed that there is an abnormality in the target liquid or the detection windows 86 and 90, and a warning can be displayed to the user by the display 64 or the indicator lights 8A-2 and 8B-2. This is because there may be dirt on the target liquid itself, or dirt may adhere to the detection windows 86 and 90, which is likely to cause abnormalities in the refractive index measurement, that is, the concentration measurement. In response to this, the user can remove the dirt adhering to the detection windows 86 and 90 and check for dirt on the target liquid itself. In conventional concentration sensors, dirt cannot be detected, so the user does not know whether there is a change in concentration (there is a change in the fluid), or whether there is no change in the fluid but dirt has adhered to the concentration sensor and maintenance is required for measurement. In contrast, in this embodiment, since dirt can be detected, the user can determine whether it is a change in the fluid or the time for regular maintenance, and there is no need to spend useless time investigating the cause.

[0056] FIG. 19 is a block diagram of the plug-in type 8A and the water-flow type 8B refractive index formula concentration sensors 8 according to this embodiment. The refractive index formula concentration sensors 8, both the plug-in type 8A and the water-flow type 8B, have only one signal cable to the outside. As shown in FIG. 1, it is connected to the refractive index formula concentration sensor 8 from the clamp-on ultrasonic flow switch 6 via a branch connector. It is connected by one cable including a power line and a communication line from the ultrasonic flow switch 6. The signal line is divided into a power line and a communication IF section inside the refractive index formula concentration sensor. The power line supplies power to each circuit element in the refractive index formula concentration sensor. The communication IF is for performing bidirectional communication from the flow switch 6 to the concentration sensor 8 and from the concentration sensor 8 to the flow switch 6. The control unit CB(m) controls the LED substrate (LED light source 102), irradiates the prisms 130 and 140 with light, receives the light reflected by the liquid with the CMOS substrate 106, and converts it into a refractive index according to the received position. A monitor PD103 is provided near the LED light source 102 of the LED substrate to monitor the light emission amount of the LED. According to the light emission amount of the LED light source 102, the current supplied to the LED light source 102 is adjusted to control the light emission amount to be constant. The indicator lights 8A-2 and 8B-2 change their lighting states according to the light reception state and refractive index at the CMOS substrate 106. On the liquid surface side of the refractive index formula concentration sensor 8, there is a temperature measurement circuit 40 including a thermometer. The temperature of the fluid may be displayed according to the temperature obtained by the thermometer of the temperature measurement circuit 40. Also, since there is a change in the refractive index of the liquid due to temperature, in order to correct this temperature dependence, the obtained concentration may be corrected using the liquid temperature.

[0057] Here, the refractive index concentration sensors 8A and 8B can also detect "dirt detection" of the detection windows 86 and 90, and can also detect that the fluid is in a dry water state ("dry water detection").

[0058] "Dirt detection" determines whether dirt is attached to the detection windows 86 and 90 based on the received light waveform obtained by the image sensor 106. When the fluid S is present and there is no dirt on the detection windows 86 and 90, there are areas with a large amount of received light and areas with a small amount of received light. By performing a predetermined operation on the waveform signal obtained by differentiating the received light waveform, it is possible to determine whether there is dirt on the detection windows 86 and 90. When it is determined that there is dirt on the detection windows 86 and 90, the indicator lights 8A-2 and 8B-2 are used to notify the user that there is dirt. Here, when there is dirt, the received light waveform changes gently, so the signal intensity, peak width, etc. of the waveform obtained by differentiation change from the state without dirt.

[0059] Referring to FIG. 20, for "dry water detection", among the light-receiving regions of the image sensor 106, the pixels in the region not used for measuring the refractive index are used for dry water detection. That is, in the CMOS image sensor 106, there are pixel positions that do not receive a light signal even when the liquid concentration is 0%. Those pixels are used as dry water detection pixels.

[0060] When there is liquid in the fluid, light from the LED light source 102 does not enter the pixels corresponding to an angle smaller than the critical angle according to the refractive index of the liquid. Therefore, the amount of light received by the pixels for dry water detection becomes zero or nearly zero. On the other hand, when there is no liquid in the fluid, air exists at the interface with the detection windows 86 and 90, and the amount of light received by the pixels for dry water detection increases. When the amount of light received by the pixels for dry water detection exceeds a certain threshold, it is determined that dry water has occurred, and it is indicated on the indicator lights 8A-2 and 8B-2 or the display 64 that it is dry water.

[0061] Both the level of dry water detection and the level of dirt detection can be set by the user, and can be selected such as "low", "medium", "high", or levels 1 to 4. This selection is possible by user input to the display 64, and the levels of dry water detection and dirt detection can be changed. Depending on the fluid being used and the surrounding environment, the likelihood of dry water and dirt generation changes. Keeping this fact in mind, uniform dry water and dirt detection is not appropriate. Therefore, as described above, it can be set by the user.

[0062] Using FIG. 21, the method for calculating the concentration by the refractive index formula concentration sensor according to this embodiment will be described. This is common to both the water flow type and the insertion type. First, as St1, initial settings are made. In the display 64 attached to the flow rate sensor in FIG. 22, a large display lamp 64b is provided at the upper part of the display unit 64a, and an operation unit 64c is provided at the lower part of the display (FIG. 22). With this operation unit 64c, it is possible to input settings according to the screen appearing on the display unit 64a. By inputting to the operation unit 64c, the unit of concentration and the threshold value displayed on the display unit 64a are set.

[0063] Next, as St2, the light projection from the LED light source 102 is controlled. Timing control is performed to emit pulsed light. This is to increase the noise resistance against ambient light. By canceling the received light signal during non-light emission during pulsed light emission, etc., the noise of ambient light can be removed.

[0064] Also, in the LED light source 102, the light emission amount is controlled. The monitor PD103 monitors the light emission amount of the LED light source 102, and controls the LED light source 102 so that the light emission amount becomes constant. By controlling the light emission amount of the LED light source 102 after the next timing based on the received light signal in the monitor PD103, the light emission amount from the light projection side is made constant, the received light amount in the imaging element is made constant, and the signal processing of the received light waveform becomes easy. This leads to an improvement in accuracy.

[0065] Next, as St3, light is received by the imaging element (CMOS substrate) 106. The imaging element 106 is arranged in the housing such that each pixel is arranged at a position corresponding to the reflection angle in the detection window 86. The imaging element 106 acquires the light reception distribution. At this time, exposure control is performed in synchronization with the lighting timing of pulsed light emission on the light emitting element side. By removing the received light amount during non-light emission as ambient light from the received light waveform signal, countermeasures against ambient light can be taken.

[0066] Next, as St4, based on the light reception distribution as shown in FIG. 20 obtained by the imaging device 106, the pixel positions of the light and dark lines are determined. Since the reflection angle changes depending on the concentration of the liquid, the position where light and dark occur changes depending on the concentration. By utilizing the change in the refractive index due to the concentration in this way and using the correspondence between the refractive index and the concentration, the concentration is converted from the refractive index.

[0067] Here, as shown in St5, concentration correction is performed based on the temperature. This is because the correspondence between the refractive index and the concentration changes depending on the temperature of the liquid, so correction based on the temperature is performed when converting from the refractive index to the concentration using the temperature acquired by the temperature measurement circuit 40.

[0068] As shown in St6, abnormality detection is performed based on the light reception waveform and the light reception signal in the imaging device 106. For dry water detection, the pixels for dry water detection in the imaging device 106 are used. For dirt detection, it is determined based on the steepness of the change in light and dark in the light reception waveform. Also, if there is a lot of ambient light and the light reception signal is high in the concentration detection range, it is possible to determine that there is ambient light. Note that the abnormality detection may be performed in parallel with the concentration calculation and correction, or may be performed before the concentration calculation and correction.

[0069] Summarizing St3 to 6, in order to measure the concentration, in order to obtain the refractive index that has a correlation with the concentration, the light and dark lines of the light reception waveform that change according to the critical angle are obtained. Although the refractive index has a correlation with the concentration, since there is a difference due to the temperature, the conversion table from the refractive index to the concentration is corrected based on the temperature, and the concentration is measured.

[0070] As St7, the obtained concentration is displayed on the display unit 64a of the display 64. The threshold value is compared with the current location, and the result is displayed on the display lamp 64b of the display 64. Also, the content of the abnormality detection may be displayed on the display unit 64a of the display 64, and the lighting state or the blinking state corresponding to the abnormality content may be performed via the display lamp 64b.

[0071] As shown in FIG. 24, as a stability warning, it is possible to set a warning threshold for the dirt on the detection window 86. If the threshold is set low, even a little dirt will cause the display lights 64b and 8A-2, 8B-2 of the display 64 to output a warning indicating that there is dirt on the detection window and prompting maintenance of the detection window. If the threshold is set high, no warning will be output unless the dirt is relatively heavy. Depending on the properties of the liquid S and the properties of the solute in the liquid S, the user can change the warning threshold.

[0072] The dry water detection sensitivity can also be changed by input to the operation unit, and it can be turned off, and the sensitivity setting can be changed. When the sensitivity is set high, if there is even a little dry water on the detection window, or in the case of a plug-in type, when the liquid level in the tank drops and part of the window becomes the liquid level and the part above that becomes dry water, a warning display can be made.

[0073] The teaching target value is so-called zero point adjustment. A target value is set for a certain liquid that serves as a reference for concentration, and the concentration standard is adjusted. Such setting is possible through the operation unit 64c and the display 64a.

[0074] As described above, the embodiments of the present invention have been described in relation to the ultrasonic flow rate detection device. However, the present invention can be widely and generally applied to a refractive index type concentration sensor regardless of its relation to the ultrasonic flow rate detection device.

Explanation of Reference Numerals

[0075] 8 Refractive index type concentration sensor 8A Plug-in type concentration sensor 8A-1 Detection part of plug-in type concentration sensor 8B Water-flowing type concentration sensor 8B-1 Detection part of water-flowing type concentration sensor 86 Detection window of plug-in type concentration sensor 90 Detection window of water-flowing type concentration sensor 102 LED light source 104 Prism 104a First surface of prism (surface on the light projection part side) The second surface of the prism in contact with the liquid to be measured 104b The third surface of the prism (the surface on the light-receiving part side) 104c Image sensor 106 Light-projecting part 110 Light-projecting lens (collimator lens) 112 Diffusion plate 114 Light-receiving part 120 Light-receiving lens (condensing lens) 122 Polarizing plate 128 Quartz prism adopted by the insertion type concentration sensor (polishing & hydrophilic coating applied) 130 Sapphire prism adopted by the water-flow type concentration sensor (polarizing plate arranged) 140 Holder 200

Claims

1. A refractive index type concentration sensor for measuring the concentration of a coolant containing a water-soluble cutting oil agent, a light source, a projection lens that converts the light emitted from the light source into substantially parallel light, a surface light source composed of a diffusion plate that diffuses the substantially parallel light generated by passing through the projection lens and converts the substantially parallel light into light having a plurality of angular components, a prism having a first surface for receiving light from the surface light source, a second surface in contact with the coolant containing the water-soluble cutting oil agent to be measured and reflecting according to the refractive index of the measurement target, and a third surface for extracting the reflected light, a light receiving lens for receiving the reflected light received at the third surface of the prism, an image sensor that receives the reflected light through the light receiving lens and acquires a light quantity distribution corresponding to the reflected light, a circuit board for calculating the concentration of the coolant based on the position of the bright and dark lines generated by the critical angle determined based on the light quantity distribution acquired by the image sensor and the correspondence relationship between the refractive index and the concentration, a holder that presses the prism in a state where the second surface of the prism is exposed from the inside to the outside, a refractive index type concentration sensor having a housing that houses the light source, the projection lens, the diffusion plate, the light receiving lens, the image sensor, the substrate, the holder, and the prism.

2. In the refractive index type concentration sensor according to Claim 1, the housing has a detection window that exposes the second surface to the liquid to be measured, and the detection window and the second surface are flush.

3. In the refractive index type concentration sensor according to Claim 2, the prism is composed of a quartz prism, and the second surface of the quartz prism in contact with the liquid to be measured is polished and provided with a hydrophilic coating.

4. In the refractive index type concentration sensor according to Claim 2 or 3, the housing has a detection part and a rod-shaped part extending from the detection part, a refractive index type concentration sensor that uses the detection part facing down with respect to the liquid, the rod-shaped part provided in the vertical direction, and the detection window facing substantially horizontally.

5. In the refractive index type concentration sensor according to Claim 4, the refractive index type concentration sensor is operated with the detection part of the refractive index type concentration sensor inserted into the liquid to be measured.

6. In the refractive index type concentration sensor according to Claim 4 or 5, The detection unit is arranged at one longitudinal end of the refractive index formula concentration sensor, and an indicator light is arranged at the other end. When the concentration of the liquid to be measured exceeds the threshold value, the indicator light is turned on or off.

7. In the refractive index formula concentration sensor according to claim 1 or 2, the prism is composed of a sapphire prism, and a polarizing plate is interposed between the first surface of the sapphire prism and the diffusion plate.

8. In the refractive index formula concentration sensor according to claim 7, the refractive index formula concentration sensor is operated in a state where the detection unit of the refractive index formula concentration sensor faces the inside of a pipe through which the liquid to be measured flows.

9. In the refractive index formula concentration sensor according to claim 8, it is provided with terminals for connecting the refractive index formula concentration sensor to the outside, and an indicator light is arranged on the terminals. When the concentration of the liquid to be measured exceeds the threshold value, the indicator light is turned on or off.

10. In the refractive index formula concentration sensor according to claim 6 or 9, based on the absolute value of the amount of light received by the imaging element, when the absolute value is abnormal, an alarm is displayed by the indicator light.

11. In the refractive index formula concentration sensor according to claim 10, based on the absolute value of the amount of light received when there is no liquid on the second surface, when the object to be measured does not exist, the indicator light displays an alarm.

12. In the refractive index formula concentration sensor according to any one of claims 1 to 11, a water stop member is interposed between the prism and the housing.

13. In the refractive index formula concentration sensor according to any one of claims 1 to 12, near the light source, it has a PD for monitoring, and based on the amount of light received by the PD for monitoring, the light source is controlled to adjust the light emission amount.

14. In the refractive index formula concentration sensor according to any one of claims 1 to 13, inside the housing, it has a temperature sensor, and the refractive index or concentration is corrected according to the temperature obtained by the temperature sensor.

15. In the refractive index formula concentration sensor according to any one of claims 1 to 14, among the housings, the portion engaged with the prism has a stepped portion, among the prisms, the portion engaged with the housing has a stepped portion.

Images