Patent Publication Number: US-2018044898-A1

Title: Water discharging device

Description:
TECHNICAL FIELD 
     The present invention relates to a water discharging device, and more particularly to a water discharging device that discharges water so as to spread the water from a water discharge port. 
     BACKGROUND ART 
     Conventionally, various attempts are made for saving water in a water discharging device. Among these, spray water discharge in which misty water is discharged at a low flow rate (water is discharged in such a manner that water spreads from a water discharge port) is effective for water saving. This spray water discharge is useful in being capable of discharging water over a wide range while saving water. 
     For example, Patent Document 1 discloses a configuration of a nozzle for the above spray water discharge. Additionally, for example, Patent Document 2 discloses a hand wash basin that performs spray water discharge of electrolyzed water having a sterilizing function to sterilize hands. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Patent Laid-Open No. 2004-050121 
     Patent Document 2: Japanese Patent Laid-Open No. 11-241381 
     SUMMARY OF INVENTION 
     Technical Problem 
     The above spray water discharge is effective for water saving, but has a higher flow speed than general water discharge (for example, foamy water discharge, shower water discharge, and the like), and therefore is likely to cause water splash. Therefore, the inventors of the present invention have considered to find out a parameter involved in water splash in the spray water discharge and implement spray water discharge that does not cause the water splash. 
     The present invention has been made in order to solve the above problem, and an object of the present invention is to suitably inhibit water splash in a water discharging device that discharges water so as to spread the water from a water discharge port. 
     Solution to Problem 
     In order to achieve the above object, the present invention is a water discharging device that is provided so as to secure a predetermined opened space with respect to a water receiving part, and discharges water toward the water receiving part, the water discharging device includes a water discharge part that jets waterdrops so as to spread the waterdrops at a predetermined angle from a water discharge port, and is set so as to discharge water at a predetermined flow rate, wherein an average flow speed X (m/sec) and an average particle size Y (μm) of the waterdrops jetted from the water discharge part satisfy a following conditional expression (1). 
         Y≦ 9300× X   (−1.5)   (1)
 
     In the present invention thus configured, in the water discharging device that jets the waterdrops toward the water receiving part so as to spread the waterdrops at the predetermined angle from the water discharge port, the average flow speed and the average particle size of the waterdrops jetted from the water discharge part satisfy the above conditional expression (1), and therefore it is possible to suitably inhibit water splash by the waterdrops jetted from the water discharge part while securing water saving and water discharge over a wide range. 
     In the present invention, the average flow speed X and the average particle size Y of the waterdrops jetted from the water discharge part further satisfy a following conditional expression (2). 
         Y≧− 360× X+ 1500  (2)
 
     In the present invention thus configured, the average flow speed and the average particle size of the waterdrops jetted from the water discharge part satisfy the above conditional expression (2), and therefore it is possible to secure suitable washing performance (such as hand washing performance) by water discharge of the water discharge part. 
     In the present invention, the average flow speed X of the waterdrops jetted from the water discharge part is equal to or larger than 1.7 (m/sec). 
     In the present invention thus configured, the average flow speed of the waterdrops jetted from the water discharge part is 1.7 (m/sec) or more, and therefore it is possible to suitably implement a water discharge form in which the waterdrops are jetted so as to spread at the predetermined angle from the water discharge port. 
     In the present invention, the average particle size Y of the waterdrops jetted from the water discharge part is equal to or larger than 35 (μm). 
     In the present invention thus configured, the average particle size of the waterdrops jetted from the water discharge part is 35 (μm) or more, and therefore the waterdrops jetted from the water discharge part can be suitably lowered without floating. Consequently, the waterdrops jetted from the water discharge part can suitably reach, for example, an object such as hands of a user which stretch out toward the water discharge part. 
     In the present invention, the average particle size Y of the waterdrops jetted from the water discharge part is equal to or smaller than 9000 (μm). 
     In the present invention thus configured, the average particle size of the waterdrops jetted from the water discharge part is 9000 (μm) or less, and therefore it is possible to suitably inhibit split of the waterdrops jetted from the water discharge part on the way. Consequently, it is possible to easily perform control for inhibiting water splash. 
     In the present invention, the water discharge part jets the waterdrops so as to spread the waterdrops at from 40 to 50 degrees as the predetermined angle. 
     In the present invention thus configured, an angle corresponding to a range when water is discharged from the water discharge port (discharge angle) is set to 40 to 50 degrees, and therefore whole hands of a user can be covered by water discharge from the water discharge part, and hand washing performance can be improved. 
     Advantageous Effects of Invention 
     According to the present invention, in a water discharging device that jets waterdrops so as to spread the waterdrops from a water discharge port, waterdrops having suitable flow speeds and particle sizes are jetted, so that it is possible to suitably inhibit water splash. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a hand wash basin to which a water discharging device according to the embodiment of the present invention is applied, as viewed obliquely from above. 
         FIGS. 2A and 2B  are diagrams for specifically illustrating a configuration of the water discharging device according to the embodiment of the present invention, in which  FIG. 2A  is a perspective view of this water discharging device as viewed obliquely from below, and  FIG. 2B  is a sectional view of this water discharging device taken along the line IIB-IIB in  FIG. 2A . 
         FIG. 3  is a longitudinal sectional view of a water discharge part for illustrating a principle of spray water discharge of the water discharge part according to the embodiment of the present invention. 
         FIG. 4  is a whole configuration diagram of a measurement system used to measure water splash in the embodiment of the present invention. 
         FIGS. 5A and 5B  each are a diagram illustrating an example of a measurement result obtained by the measurement system according to the embodiment of the present invention. 
         FIGS. 6A and 6B  each are a diagram illustrating another example of a measurement result obtained by the measurement system according to the embodiment of the present invention. 
         FIG. 7  is an explanatory diagram of an upper limit boundary line of the average flow speed and the average particle size of waterdrops jetted from the water discharging device according to the embodiment of the present invention. 
         FIG. 8  is an explanatory diagram of a lower limit boundary line of the average flow speed and the average particle size of waterdrops jetted from the water discharging device according to the embodiment of the present invention. 
         FIG. 9  is a diagram illustrating a water discharge form by the water discharging device in a case where a flow rate applied to the water discharging device according to the embodiment of the present invention is variously changed. 
         FIG. 10  is an explanatory diagram of a suitable range of the average flow speed and the average particle size of the waterdrops jetted from the water discharging device according to the embodiment of the present invention. 
         FIG. 11  is a perspective view of a kitchen as viewed obliquely from above, the kitchen being a kitchen to which a water discharging device according to a modification in the embodiment of the present invention is applied. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a water discharging device according to the embodiment of the present invention will be described with reference to the attached drawings. 
     Device Configuration 
     First, a configuration of the water discharging device according to the embodiment of the present invention will be described with reference to  FIG. 1  to  FIG. 3 . 
       FIG. 1  is a perspective view of a hand wash basin to which the water discharging device according to the embodiment of the present invention is applied, as viewed obliquely from above. As illustrated in  FIG. 1 , a hand wash basin  1  mainly has a water discharging device  2  that mistily performs water discharge (spray water discharge/misty water discharge) so as to spread water from a water discharge port as illustrated by reference numeral M, and a bowl  3  that receives the water discharged from this water discharging device  2 , and drains the water from a drain port (not illustrated), and serves as a water receiving part. 
       FIGS. 2A and 2B  are diagrams for specifically illustrating the configuration of the water discharging device according to the embodiment of the present invention.  FIG. 2A  is a perspective view of the water discharging device according to the embodiment of the present invention as viewed obliquely from below, and  FIG. 2B  is a sectional view of this water discharging device taken along the line IIB-IIB in  FIG. 2A . 
     As illustrated in  FIGS. 2A and 2B , the water discharging device  2  has a water discharge pipe  11  that is a curved tubular member. In a front end of the water discharge pipe  11 , a nozzle-like water discharge part  13  configured to perform spray water discharge (misty water discharge) in which water spreads at a predetermined angle from a water discharge port  13   a , and a sensor  14  that detects an object to be detected by utilizing infrared light or the like are disposed. Additionally, inside the water discharge pipe  11 , a flow path  15  that is connected to the water discharge part  13 , and supplies water to the water discharge part  13  is disposed. The water discharging device  2  detects the object to be detected such as a human body by use of the sensor  14  to switch between execution and stop of water discharge from the water discharge part  13 . 
     Now, a principle of the spray water discharge of the water discharge part  13  according to this embodiment will be described with reference to  FIG. 3 .  FIG. 3  is a schematic diagram obtained by enlarging a longitudinal sectional view of the water discharge part  13  as viewed along the water flow direction. 
     As illustrated in  FIG. 3 , in the water discharge part  13 , a straight flow (refer to the arrow A 11 ) is generated inside an internal flow path  13   d  by water that flows in from an inflow port  13   b  provided in an upper end, and a rotational flow (refer to the arrow A 12 ) is generated inside the internal flow path  13   d  by water that flows in from a slit part  13   c  formed on an outer peripheral surface of the upper end of the internal flow path  13   d . The spray water discharge is performed in a full-cone manner from the water discharge port  13   a  formed in a lower end of the internal flow path  13   d , by a synergistic effect of such a straight flow and such a rotational flow. More specifically, while spreading in a range larger than the cross-sectional area (opening diameter) of the water discharge port  13   a , the water is intermittently discharged, in other words, waterdrops are jetted. In this case, as illustrated in  FIG. 3 , water spreads at a predetermined discharge angle θ from the water discharge port  13   a  to be discharged. For example, this discharge angle θ may be set to 40 to 50 degrees to cover a whole of hands of a user by the spray water discharge from the water discharge part  13 . 
     As described above, in this specification, word “spray water discharge” means that water is intermittently discharged so as to spread at the predetermined angle θ from the water discharge port  13   a  of the water discharge part  13 , in other words, waterdrops are jetted. 
     The water discharge port  13   a  of the water discharge part  13  has a cross-sectional area smaller than a water discharge port of a general water discharge part (for example, a water discharge part for performing foamy water discharge or shower water discharge), and therefore has strong resistance, and generates pressure reducing action. Therefore, at least one of a constant flow valve, a pressure regulating valve, and a constant-pressure valve may be provided on an upstream side of the flow path  15  of the above water discharging device  2  (not illustrated in  FIGS. 2A and 2B ), and water may be supplied to the water discharge part  13  at a predetermined flow rate and/or with predetermined pressure. These valves are suitably adjusted, so that the flow speed and the particle size (strictly, the average flow speed and the average particle size) in the spray water discharge from the water discharge part  13  are set to respective desired values. 
     In the above example, an automatic water discharging device that detects an object to be detected such as a human body by using the sensor  14  to automatically switch between water discharge and stop of the water discharge is described as the water discharging device  2  (refer to  FIGS. 2A and 2B ). However, the present invention is not limited to application to such an automatic water discharging device, and can be applied to a water discharging device that manually performs water discharge and stop of the water discharge. 
     Flow Speed and Particle Size of Spray Water Discharge 
     Now, the flow speed and the particle size of the spray water discharge by the water discharge part  13  of the water discharging device  2  according to the embodiment of the present invention will be described. More specifically, the average flow speed and the average particle size of waterdrops jetted from the water discharge part  13 , which are to be applied to the water discharging device  2  according to this embodiment, will be described. The inventors of the present invention investigate ranges of the average flow speed and the average particle size of waterdrops that are to be jetted from the water discharge part  13  of the water discharging device  2  by conducting various measurement described below. 
     Herein, for the “average flow speed” of the waterdrops jetted from the water discharge part  13  of the water discharging device  2 , the average flow speed at a position separated from the water discharge port  13   a  of the water discharge part  13  by 100 (mm) is used. The “average flow speed” of the waterdrops is equivalent to the moving speed of the waterdrops. On the other hand, for the “average particle size” of the waterdrops jetted from the water discharge part  13  of the water discharging device  2 , a Sauter average value (total volume/total surface area) based on a particle size distribution, which is obtained by a Fraunhofer analysis method utilizing a He—Ne laser is used. This “average particle size” of the waterdrop is equivalent to the diameter of the waterdrop. 
     The reason why such “average flow speed” and such “average particle size” are used is because there is a distribution in each of the flow speeds and the particle sizes of the waterdrops jetted from the water discharge part  13 , and the flow speeds and the particle sizes are not uniform. 
     (1) Upper Limit Boundary Line of Flow Speed and Particle Size 
     First, an upper limit boundary line of the average flow speed and the average particle size of the waterdrops jetted from the water discharge part  13  of the water discharging device  2  according to this embodiment will be described. This upper limit boundary line is determined from a viewpoint of inhibiting water splash by the waterdrops jetted from the water discharge part  13  of the water discharging device  2  according to this embodiment. 
       FIG. 4  is a whole configuration diagram schematically illustrating a measurement system used in order to measure water splash in the embodiment of the present invention. 
     As illustrated in  FIG. 4 , a measurement system  50  has a water discharging device  51  that jets a waterdrop WD, and can variously set the flow speed and the particle size of this waterdrop WD, a frosted glass  52  with which the waterdrop WD jetted from this water discharging device  51  collides, a scale  53  placed on this frosted glass  52 , a high-speed camera  54  that photographs a range including at least a surface of the frosted glass  52  with which the waterdrop WD collides, a lighting  55  that irradiates the frosted glass  52  from above with light, a lighting  56  that irradiates the frosted glass  52  from below with light, and a PC (personal computer)  57  that receives supplied image data photographed by the high-speed camera  54  to process this image data. 
     More specifically, the frosted glass  52  has size of 300 (mm)×300 (mm)×5 (mm). Additionally, a water discharge port of the water discharging device  51  and a surface of the frosted glass  52  are separated by 100 (mm). The high-speed camera  54  photographs with resolution of 1280 (pixels)×800 (pixels) at a high speed of 10000 (frames/second). Furthermore, the pressure and the flow rate of water supplied to the water discharging device  51  are adjusted, the opening diameter of a water discharge port applied to the water discharging device  51  is changed, or the width of a slit applied to the inside of the water discharging device  51  is changed, so that the flow speed and the particle size of the waterdrop WD jetted from the water discharging device  51  are changed. The incident angle of the waterdrop WD jetted from the water discharging device  51  on the frosted glass  52  is constant. 
     Herein, in this embodiment, a water film WF is formed on the frosted glass  52 , and water splash when the waterdrop WD collides with this water film WF is measured. Not a hand in a dry state at an initial stage of hand washing (that is, a state where no water film is formed on a surface of the hand), but a hand in a wet state at a middle and subsequent stage of the hand washing (that is, a state where the water film is formed on the surface of the hand) is assumed, and the hand in this wet state is simulated by the frosted glass  52  with the water film WF formed thereon, so that water splash caused in the hand in the wet state is attempted to be investigated. 
     Water splash is more likely to be caused in the dry state than the wet state. This reason is as follows. In a case where a collision object is in the dry state, that is, in a state where a water film is not formed on a surface of the collision object, frictional force between water and the collision object, adsorption power of water, and surface tension of water mainly act, so that water splash is unlikely to be caused. On the other hand, in a case where the collision object is in the wet state, that is, in a state where the water film is formed on the surface of the collision object, the frictional force between water and the collision object (including the water film) is decreased, pressure generated at the time of collision escapes toward an external air side (side on which pressure is low), force generated at this time, which lifts the water film becomes larger than the surface tension, so that the water film bursts to be likely to cause water splash. 
     Now, the measurement procedure of water splash according to this embodiment will be described. First, the water film WF is formed on the frosted glass  52 . In this case, the frosted glass  52  is hydrophilic, and therefore water merely flows on the surface, so that the water film WF is formed. Then, the waterdrop WD is jetted from the water discharging device  51  toward the frosted glass  52 . In this case, in order to adjust focus related to jetting of the waterdrop WD from the water discharging device  51  to the frosted glass  52 , a slit of 5 (mm)×10 (mm) is applied to the water discharging device  51 . From both the two lighting  55 ,  56 , the frosted glass  52  is irradiated with light, so that the vicinity of a collision place of the waterdrop WD on the frosted glass  52  is photographed by the high-speed camera  54  in this state. 
     The PC  57  processes an image photographed by the high-speed camera  54 , and obtains the particle size of the waterdrop WD. In this case, the PC  57  analyzes the photographed image including the waterdrop WD and the scale  53  to obtain a length on the photographed image corresponding to 1 (mm) of the scale  53 , and the particle size of the waterdrop WD on the photographed image, so that the actual particle size of the waterdrop WD is obtained from a ratio of these two values. Then, the PC  57  processes the image photographed by the high-speed camera  54  to obtain the flow speed of the waterdrop WD (equivalent to the moving speed of the waterdrop WD). In this case, the PC  57  analyzes the photographed image including the waterdrop WD and the scale  53  to obtain an actual moving distance (obtained by a method similar to the above method for obtaining the particle size of the waterdrop WD) from a distance on the photographed image where the waterdrop WD moves during the predetermined number of frames, so that the flow speed of the waterdrop WD is obtained from this actual moving distance. Then, a measurer visually recognizes the water film WF and the waterdrop WD included in the photographed image to determine whether or not water splash occurs by collision of the waterdrop WD with the water film WF. The “water splash” mentioned herein means that the waterdrop WD collides with the water film WF, the water film WF is lifted, the lifted water film WF bursts (splits), and a waterdrop splashes. 
       FIGS. 5A and 5B  illustrate examples of a measurement result obtained by the measurement system  50  according to the embodiment of the present invention. More specifically,  FIGS. 5A and 5B  illustrate examples of photographed images when the particle sizes of the waterdrop WD are constant, and the flow speeds of the waterdrop WD are different. More specifically,  FIG. 5A  illustrates an example of a photographed image when the flow speed of the waterdrop WD is 3 (m/sec),  FIG. 5B  illustrates an example of a photographed image when the flow speed of the waterdrop WD is 5 (m/sec), and the particle size of the waterdrop WD is fixed to 750 (μm) when these flow speeds are applied. In addition, the incident angle of the waterdrop WD to the frosted glass  52  (including the water film WF) is fixed to 90 degrees. In each of  FIGS. 5A and 5B , the photographed images are arranged in order from the left to the right in time series. For convenience of explanation, images corresponding to the waterdrop WD are circled, and bars are added to the vicinity of places where water splash occurs on the images. 
     As illustrated in  FIG. 5A , it is found that water splash does not occur (refer to reference numeral A 21 ), in a case where the flow speed of the waterdrop WD is 3 (m/sec). As illustrated in  FIG. 5B , it is found that water splash occurs (refer to reference numeral A 22 ), in a case where the flow speed of the waterdrop WD is 5 (m/sec). Consequently, it can be said that water splash is likely to be caused, when the flow speed of the waterdrop WD becomes large. 
       FIGS. 6A and 6B  are diagrams illustrating another example of a measurement result obtained by the measurement system  50  according to the embodiment of the present invention. More specifically,  FIGS. 6A and 6B  illustrate examples of photographed images when the flow speeds of the waterdrop WD are constant, and the particle sizes of the waterdrop WD are different. More specifically,  FIG. 6A  illustrates an example of a photographed image when the particle size of the waterdrop WD is 400 (μm),  FIG. 6B  illustrates an example of a photographed image when the particle size of the waterdrop WD is 820 (μm), and the flow speed of the waterdrop WD is fixed to 4 (m/sec) when the above particle sizes are applied. In addition, the incident angle of the waterdrop WD to the frosted glass  52  (including the water film WF) is fixed to 90 degrees. In each of  FIGS. 6A and 6B , the photographed images are arranged in order from the left to the right in time series. For convenience of explanation, images corresponding to the waterdrop WD are circled, and bars are added to the vicinity of places where water splash occurs on the images. 
     As illustrated in  FIG. 6A , it is found that water splash does not occur (refer to reference numeral A 31 ), in a case where the particle size of the waterdrop WD is 400 (μm). As illustrated in  FIG. 6B , it is found that water splash occurs (refer to reference numeral A 32 ), in a case where the particle size of the waterdrop WD is 820 (μm). Consequently, it can be said that water splash is likely to be caused, when the particle size of the waterdrop WD becomes large. 
     In this embodiment, the flow speed and the particle size of the waterdrop WD jetted from the water discharging device  51  were set to respective various values, and it was measured whether or not water splash occurs in combinations of various flow speeds and particle sizes by the above method. The results are illustrated in  FIG. 7 . 
       FIG. 7  is a diagram illustrating the presence or absence of water splash measured in the combinations of the various flow speeds and particle sizes applied to the waterdrop, and a diagram for illustrating an upper limit boundary line of the average flow speed and the average particle size of waterdrops jetted from the water discharging device  2  according to the embodiment of the present invention. 
     In  FIG. 7 , a horizontal axis represents the flow speed (m/sec) of the waterdrop, and a vertical axis represents the particle size (μm) of the waterdrop. More specifically, the circles drawn by “◯” in  FIG. 7  denote a flow speed and a particle size when it is determined by measurement that water splash does not occur, and the crosses drawn by “×” in  FIG. 7  denote a flow speed and a particle size when it is determined by measurement that water splash occurs. By such measurement results, a region defined by the flow speed and the particle size can be divided into a region R 1  where water splash occurs, and a region R 2  where water splash does not occur, by using a curved line L 1  illustrated in  FIG. 7  as a boundary line. This curved line L 1  can be expressed by the following approximate expression (3) by using a flow speed x (m/sec) and a particle size y (μm). 
         y= 9300× x   (−1.5)   (3)
 
     In this embodiment, the curved line L 1  expressed by the above expression (3) is used as the upper limit boundary line of the average flow speed and the average particle size of waterdrops jetted from the water discharging device  2 . That is, as a conditional expression which the average flow speed X (m/sec) and the average particle size Y (μm) of the waterdrops jetted from the water discharging device  2  should satisfy, the following expression (4) based on the expression (3) is used. When such expression (4) is satisfied by the average flow speed X (m/sec) and the average particle size Y (μm) of the waterdrops jetted from the water discharging device  2 , it is possible to suitably inhibit water splash by the waterdrops jetted from the water discharging device  2 . 
         Y≦ 9300× X   (−1.5)   (4)
 
     (2) Lower Limit Boundary Line of Flow Speed and Particle Size 
     Now, the lower limit boundary line of the average flow speed and the average particle size of waterdrops jetted from the water discharge part  13  of the water discharging device  2  according to this embodiment will be described. This lower limit boundary line is determined from a viewpoint of securing washing performance (dirt removing performance/hand washing performance) by the water discharging device  2  of this embodiment. 
     In this embodiment, in order to obtain the above lower limit boundary line, the following measurement procedure is performed. First, pseudo-dirt containing ethanol and Sudan Red at a mass ratio of “6:1” is created. Next, the created pseudo-dirt of 0.2 (cc) is adhered to a frosted glass with a size of 80 (mm)×80 (mm). Then, the frosted glass to which the pseudo-dirt is adhered is left for a minute, the pseudo-dirt spreads throughout the frosted glass by its own weight, and thereafter the frosted glass to which the pseudo-dirt is adhered is heated at 50 (° C.) for two minutes by a hot plate to be dried. Then, the water discharging device discharges water toward the center of the frosted glass for 5 seconds. In this case, the water discharge port of the water discharging device and a surface of the frosted glass are separated by 80 (mm). 
     The frosted glass to which the above water discharge is performed is heated at 50 (° C.) for a minute by the hot plate to be dried, and thereafter is put into a Petri dish. Next, oleic acid of 20 (cc) is dropped in a Petri dish, and the pseudo-dirt is separated from the frosted glass. Then, oleic acid and the pseudo-dirt are collected, and put into an exclusive container of a spectrophotometer to be measured. Then, a dirt removing ratio (the smaller the value is, the higher the pseudo-dirt removing degree is) indicating a pseudo-dirt removing degree is obtained from a value obtained by measurement using this spectrophotometer. More specifically, first, in order to previously perform 0 correction of the spectrophotometer, a measured value obtained when only oleic acid is used is previously obtained, the frosted glass which is in a state where the above water discharge is not performed (that is, a state where 100% of the pseudo-dirt of 0.2 (cc) remains) is previously measured, and a measured value obtained when the dirt removing ratio is a maximum value (100%) is previously obtained. Then, on the basis of the previously obtained measured values thus obtained, a dirt removing ratio (decrease rate) corresponding to a value obtained by measurement using the exclusive container of the spectrophotometer containing the collected oleic acid and pseudo-dirt this time is obtained. 
     Herein, as water discharge performed to the frosted glass to which the pseudo-dirt is adhered, spray water discharge by the water discharging device  2 , and foamy water discharge at 2 liters per minutes were applied, and the measurement results were obtained by the above procedure under a similar condition. More specifically, in a case where the spray water discharge is applied, the flow speeds and the particle sizes of waterdrops jetted by the water discharging device  2  were variously changed to be measured. In this case, various types of the water discharge part  13  are applied to the water discharging device  2  (consequently, the flow rate by the water discharge part  13  is changed), so that the flow speeds and the particle sizes of the jetted waterdrops were changed. 
     By thus measurement, in foamy water discharge at 2 liters per minute, a dirt removing ratio of 22 (%) was obtained. Then, from measurement results obtained in a case where the above spray water discharge is used, the flow speed and the particle size when the same degree of a dirt removing ratio as a dirt removing ratio of 22 (%) by the foamy water discharge at 2 liters per minute were extracted. The results are illustrated in  FIG. 8 . 
       FIG. 8  is a diagram illustrating the results of the flow speed and the particle size in a case where a dirt removing ratio of about 22 (%) is obtained by spray water discharge, and is a diagram for illustrating a lower limit boundary line of the average flow speed and the average particle size of waterdrops jetted from the water discharging device  2  according to the embodiment of the present invention. 
     In  FIG. 8 , a horizontal axis represents the flow speed (m/sec), and a vertical axis represents the particle size (μm). More specifically, the triangles drawn by “▴” in  FIG. 8  denote the flow speed and the particle size in the case where a dirt removing ratio of about 22 (%) is obtained. By such results, relation between the flow speed x (m/sec) and the particle size y (μm) in the case where a dirt removing ratio of about 22 (%) is obtained can be expressed by the following approximate expression (5) corresponding to a straight line L 2  illustrated in  FIG. 8 . 
         y=− 360× x+ 1500  (5)
 
     In this embodiment, the lower limit boundary line of the average flow speed and the average particle size of the waterdrops jetted from the water discharging device  2  is defined by the straight line L 2  expressed by the above Expression (5). That is, as a conditional expression which the average flow speed X (m/sec) and the average particle size Y (μm) of the waterdrops jetted from the water discharging device  2  should satisfy, the following expression (6) based on the expression (5) is used. When such expression (6) is satisfied by the average flow speed X (m/sec) and the average particle size Y (μm) of the waterdrops jetted from the water discharging device  2 , the same degree of a dirt removing ratio as the dirt removing ratio by the foamy water discharge at 2 liters per minute can be implemented by the spray water discharge of the water discharging device  2 . That is, it is possible to secure suitable washing performance by the spray water discharge of the water discharging device  2 . 
         Y≧− 360× X+ 1500  (6)
 
     (3) Lower Limit Value of Flow Speed 
     Now, the lower limit value of the average flow speed of the waterdrops jetted from the water discharge part  13  of the water discharging device  2  according to this embodiment will be described. This lower limit value is determined from a viewpoint of formation of suitable spray water discharge by the water discharging device  2  of this embodiment. 
     As described above, in this embodiment, a water discharge form in which water spreads in a range larger than the opening diameter of the water discharge port  13   a  of the water discharge part  13  to be intermittently discharged is applied as the spray water discharge. Whether or not such spray water discharge is suitably formed depends on the flow speed (uniquely equivalent to the flow rate) applied to the water discharging device  2 . This will be specifically described with reference to  FIG. 9 . 
       FIG. 9  is a diagram illustrating a specific example of the water discharge form by the water discharging device  2  in a case where the flow rate applied to the water discharging device  2  according to the embodiment of the present invention is variously changed.  FIG. 9  illustrates a photographed image that illustrates a water discharge form in a case where a flow rate of 0.2 (L/min) is applied, a photographed image that illustrates a water discharge form in a case where a flow rate of 0.15 (L/min) is applied, a photographed image that illustrates a water discharge form in a case where a flow rate of 0.1 (L/min) is applied, and a photographed image that illustrates a water discharge form in a case where a flow rate of 0.05 (L/min) is applied, in order from the left. 
     From  FIG. 9 , it is found that at flow rates of 0.1 to 0.2 (L/min), suitable spray water discharge is performed by the water discharging device  2 , that is, water spreads in the range larger than the opening diameter of the water discharge port  13   a  to be intermittently discharged. On the other hand, it is found that at a flow rate of 0.05 (L/min), suitable spray water discharge is not formed by the water discharging device  2 , that is, water does not spread in the range larger than the opening diameter of the water discharge port  13   a  and is not intermittently discharged. This is because at a low flow rate, a rotational flow (refer to the arrow A  12  in  FIG. 3 ) necessary for forming the suitable spray water discharge cannot be formed inside the water discharge part  13 . 
     Therefore, in this embodiment, a flow speed corresponding to the above flow rate of 0.05 (L/min) is used as a lower limit value of the average flow speed of the waterdrops jetted from the water discharge part  13  of the water discharging device  2 . In a case where the opening diameter of the water discharge port  13   a  of the water discharge part  13  is 0.8 (mm), a flow speed of about 1.7 (m/sec) is obtained from a cross-sectional area corresponding to an opening diameter of 0.8 (mm), and a flow rate of 0.05 (L/min) described above by use of a theoretical formula of “flow rate=cross-sectional area×flow speed”. In this embodiment, 1.7 (m/sec) is used as the lower limit value of the average flow speed of the waterdrops jetted from the water discharging device  2 . When such 1.7 (m/sec) is applied, and the average flow speed of the waterdrops jetted from the water discharging device  2  is set to be 1.7 (m/sec) or more, suitable spray water discharge can be formed by the water discharging device  2 , that is, water can spread in the range larger than the opening diameter of the water discharge port  13   a  to be intermittently discharged. 
     (4) Lower Limit Value of Particle Size 
     Now, a lower limit value of the average particle size of the waterdrop jetted from the water discharge part  13  of the water discharging device  2  according to this embodiment will be described. This lower limit value is determined from a viewpoint of suitably lowering the waterdrops jetted from the water discharging device  2  of this embodiment without floating the waterdrops. 
     In this embodiment, it is considered to define the lower limit value of the average particle size by using the following expression (7) obtained by converting general Stokes&#39; law. 
     
       
         
           
             
               
                 
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     In the expression (7), “d” denotes a particle size, “η” denotes the viscosity of water, “v” denotes a terminal speed, “ρ p ” denotes the density of water, “ρ f ” denotes the density of air, and “g” denotes gravitational acceleration. The terminal speed v is a speed when body force such as gravity and centrifugal force and drag which depends on a speed are balanced and are not changed in a case where an object receives the body force and the drag. In this case, the object singly moves, that is, even when another object exists, the object moves without being influenced by another object. In the expression (7), it is assumed that the speed of a particle traveling vector is zero, and an object actually freely falls in the gravity direction. 
     In this embodiment, in the above expression (7), the particle size d when terminal speed v≅0 is satisfied is used as the lower limit value of the average particle size. This is because a state of terminal speed v≅0 is equivalent to a state where the waterdrops jetted from the water discharging device  2  float without lowering. When the terminal speed v is 0, the expression (7) is not established, and therefore 1 (mm/sec) is substituted into the expression (7) as the terminal speed v. Additionally, values of water viscosity η, water density ρ p , and air density ρ f  when a water temperature and an air temperature are 5° C. are substituted into the expression (7). Consequently, a particle size d of about 35 (μm) is obtained. 
     In this embodiment, 35 (μm) thus obtained is used as the lower limit value of the average particle size of the waterdrops jetted from the water discharging device  2 . When the average particle size of the waterdrops jetted from the water discharging device  2  is set to be 35 (μm) or more by applying 35 (μm), the waterdrops jetted from the water discharging device  2  can be suitably lowered without floating. Consequently, the waterdrops jetted from the water discharging device  2  can suitably reach, for example, hands of a user. 
     (5) Upper Limit Value of Particle Size 
     Now, an upper limit value of the average particle size of the waterdrop jetted from the water discharge part  13  of the water discharging device  2  according to this embodiment will be described. 
     According to measurement performed by the inventors of the present invention, it is found that when the particle size of the waterdrop jetted from the water discharging device  2  exceeds 9000 (μm), the waterdrop splits without maintaining the particle size even in a windless state. Thus, when the waterdrops jetted from the water discharging device  2  split on the way, control becomes difficult, and water splash cannot be suitably inhibited. 
     Therefore, in this embodiment, from a viewpoint of suitably maintaining the particle sizes of the waterdrops jetted by the water discharging device  2  so as not to cause the waterdrops to split, the upper limit value of the average particle size of the waterdrops jetted from the water discharging device  2  is defined. More specifically, in this embodiment, from the above measurement results, the average particle size of the waterdrops jetted from the water discharging device  2  is set to be 9000 (μm) or less by using 9000 (μm) as the upper limit value of the average particle size of the waterdrops jetted from the water discharging device  2 . 
     (6) Suitable Range of Flow Speed and Particle size 
     Now, a suitable range of the average flow speed and the average particle size of the waterdrops jetted from the water discharge part  13  of the water discharging device  2  according to this embodiment, in accordance with contents described in the above (1) to (5) will be described with reference to  FIG. 10 . 
       FIG. 10  is an explanatory diagram of the suitable range of the average flow speed and the average particle size of the waterdrops jetted from the water discharging device  2  according to the embodiment of the present invention. In  FIG. 10 , a horizontal axis represents the flow speed (m/sec), and a vertical axis represents the particle size (μm). More specifically, in FIG.  10 , in addition to the curved line L 1  and the straight line L 2  (refer to  FIG. 7  and  FIG. 8 ) described the above (1), (2), a straight line L 3  corresponding to 1.7 (m/sec) which is the lower limit value of the average flow speed described in the above (3), a straight line L 4  corresponding to 35 (μm) which is the lower limit value of the average particle size described in the above (4), a straight line L 5  corresponding to 9000 (μm) which is the upper limit value of the average particle size described in the above (5) are overlapped. 
     As illustrated in  FIG. 10 , in this embodiment, the flow speed and the particle size in a range R 3  defined by the curved line L 1  and the straight lines L 2  to L 5  are applied as the average flow speed and the average particle size of the waterdrops jetted from the water discharging device  2  so as to satisfy all conditions described in the above (1) to (5). 
     Working Effects According to This Embodiment 
     Now, working effects of the water discharging device according to the embodiment of the present invention will be described. 
     According to this embodiment, in the water discharging device  2  that performs spray water discharge enabling water saving and water discharge over a wide range, the average flow speed and the average particle size of the waterdrops jetted from this water discharging device  2  satisfies the above conditional expression (4), so that it is possible to suitably inhibit water splash by the waterdrops jetted from the water discharging device  2 . 
     According to this embodiment, the average flow speed and the average particle size of the waterdrops jetted from the water discharging device  2  satisfy the above conditional expression (6), so that it is possible to secure suitable washing performance (such as hand washing performance) by spray water discharge of the water discharging device  2 . 
     According to this embodiment, the average flow speed of the waterdrops jetted from the water discharging device  2  is set to 1.7 (m/sec) or more, so that it is possible to form suitable spray water discharge by the water discharging device  2 . That is, it is possible to suitably implement a water discharge form in which water spreads in a range larger than the opening diameter of the water discharge port  13   a  to be intermittently discharged. 
     According to this embodiment, the average particle size of the waterdrops jetted from the water discharging device  2  is set to 35 (μm) or more, so that the waterdrops jetted from the water discharging device  2  can be suitably lowered without floating. Consequently, the waterdrops jetted from the water discharging device  2  can suitably reach, for example, hands of a user. 
     According to this embodiment, the average particle size of the waterdrops jetted from the water discharging device  2  is set to 9000 (μm) or less, so that it is possible to suitably inhibit split of the waterdrops jetted from the water discharging device  2  on the way. Consequently, it is possible to easily perform control for inhibiting water splash. 
     According to this embodiment, the discharge angle θ (refer to  FIG. 3 ) from the water discharge port  13   a  of the water discharging device  2  is set to 40 to 50 degrees, whole hands of a user can be covered by spray water discharge from the water discharging device  2 , and hand washing performance can be improved. 
     Modification 
     In the above embodiment, the average flow speed and the average particle size of the waterdrops jetted from the water discharging device  2  satisfy all the conditions of (1) to (5) described in the section of &lt;Flow Speed and Particle Size of Spray Water Discharge&gt;. However, the present invention is not limited to this. In another example, the average flow speed and the average particle size of the waterdrops jetted from the water discharging device  2  may satisfy at least one condition of any of (1) to (5) (including various combinations of the conditions of (1) to (5)). 
     In the above embodiment, general tap water (city water) is discharged from the water discharging device  2 . However, in place of this, for example, functional water (that is, disinfected water) having a disinfecting function such as electrolyzed water may be discharged. In one example, an electrolysis tank may be provided on an upstream side of a flow path  15  of a water discharging device  2 , and electrolyzed water generated by this electrolysis tank may be discharged from a water discharge part  13 . 
     In the above embodiment, the example in which the present invention is applied to a hand wash basin (refer to  FIG. 1 ) is described. However, the application of the present invention is not limited to this. In another example, the present invention can be applied to a kitchen. 
       FIG. 11  is a perspective view of a kitchen as viewed obliquely from above, the kitchen being a kitchen to which a water discharging device according to a modification in the embodiment of the present invention is applied. A kitchen  5  illustrated in  FIG. 11  mainly has a water discharging device  6  that mistily performs water discharge (spray water discharge/misty water discharge) in which water spreads from a water discharge port as illustrated by reference numeral M, a sink  7  that receives the water discharged from this water discharging device  6  to drain the water from a drain port (not illustrated), and serves as a water receiving part. A configuration similar to the configuration of the water discharging device  2  according to the above embodiment is applied to the water discharging device  6  of such a kitchen  5 , so that working effects similar to the working effects of the contents described in the section of &lt;Working Effects according to This Embodiment&gt; are obtained. 
     REFERENCE SIGNS LIST 
       1  hand wash basin 
       2 ,  6  water discharging device 
       3  bowl 
       5  kitchen 
       6  sink 
       11  water discharge pipe 
       13  water discharge part 
       13   a  water discharge port 
       15  flow path