Patent Publication Number: US-6986172-B2

Title: Flush toilet

Description:
TECHNICAL FIELD 
   The present invention relates to a flush toilet provided with a toilet body having a bowl for storing wash water as water seal and a device for supplying the toilet body with pressurized wash water. 
   BACKGROUND ART 
   A flush toilet provided with a toilet body having a bowl for storing wash water as water seal and a device for supplying the toilet body with pressurized wash water, wherein wash water led from a tank directly connected to the toilet body discharges substantially horizontally along the upper peripheral portion of the inner surface of the bowl to swirl along the inner surface of the bowl is disclosed in International Laid-Open Publication WO98/16696. The aforementioned flush toilet has an advantage in that it does not cause loud noise during its operation because the wash water swirls and goes down along the inner surface of the bowl to run into the water seal aslant. 
   The flush toilet disclosed in the International Laid-Open Publication WO98/16696 has a disadvantage in that the flow speed of the wash water swirling along the inner surface of the toilet body is low and it does not have strong detergency against the inner surface of the toilet body because the wash water with low water pressure led from the tank directly connected to the toilet body discharges substantially horizontally. 
   DISCLOSURE OF INVENTION 
   An object of the present invention is to provide a flush toilet wherein no loud noise is caused during operation, while strong detergency is achieved against the inner surface of the bowl. 
   In accordance with the present invention, there is provided a flush toilet comprising a toilet body having a bowl for storing wash water as water seal, first means for supplying the toilet body with pressurized wash water and second means for discharging the wash water substantially horizontally along the upper peripheral portion of the inner surface of the bowl to swirl it along the inner surface of the bowl. 
   The present flush toilet does not cause loud noise during its operation because the wash water swirls and goes down along the inner surface of the bowl to run into the water seal aslant. The wash water discharging from the second means is pressurized and provided with high water pressure. Therefore, the discharging wash water swirls along the inner surface of the toilet body at high speed to achieve strong detergency against the inner surface of the bowl. The wash water swirling along the inner surface of the bowl dwells on it for a long time to achieve strong detergency against it. In the present specification, the clause “pressurized wash water” means wash water provided with water pressure higher than that of wash water with about 250 mm of water head led from a tank directly connected to the toilet body. The pressurized wash water can be obtained by leading in pressurized city water directly from a water supply pipe, leading in reserved water from a tank installed on the roof of a house or a building, or leading in portable water through a pressure device such as a pump, etc. 
   In the present specification, the word “swirl” means that wash water discharging substantially horizontally substantially goes round the whole inner surface of the bowl before it reaches the water seal. When the wash water substantially goes round the whole inner surface of the bowl, it dwells on the inner surface of the bowl for a long time to enhance its detergency. When the wash water goes round half or so of the inner surface of the bowl before it reaches the water seal, the movement of the wash water does not correspond to “swirl”. 
   In accordance with a preferred embodiment of the present invention, the flush toilet comprises a plurality of the second means. 
   Each wash water discharging from a plurality of the second means washes the inner surface of the bowl to enhance the detergency of the flush toilet. The wash waters may swirl in the same direction or in different directions. 
   In accordance with a preferred embodiment of the present invention, the inner surface of the bowl comprises an overhang at its upper end. 
   The overhang prevents the pressurized wash water discharging from the second means substantially horizontally from flowing out the bowl beyond the upper periphery of the bowl. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises a trap-way extending from the bottom of the bowl and third means for discharging wash water to direct it to an inlet of the trap-way. 
   A trap-way enables flushing of soil out the toilet body to enhance the efficiency of flushing soil. When the wash water discharging from the third means is directed to an inlet of the trap-way, the trap-way is filled up with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   In accordance with a preferred embodiment of the present invention, the third means discharges pressurized wash water. 
   When the third means discharges pressurized wash water, the trap-way is filled up with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises fourth means for supplying non-pressurized wash water, and the third means discharges non-pressurized wash water. 
   Non-pressurized wash water led from a tank directly connected to the toilet body may be discharged from the third means in a district or in a house where pressurized wash water with ample flow rate cannot be obtained. 
   In accordance with a preferred embodiment of the present invention, the third means discharges the wash water below the water plane of the water seal. 
   The wash water discharging below the water plane of the water seal forces soil depositing on the bottom of the bowl directly into the trap-way to enhance the efficiency of flushing soil. 
   In accordance with a preferred embodiment of the present invention, the third means makes the discharging wash water swirl in the same direction as the pressurized wash water discharging from the second means. 
   When the wash water discharging from the third means swirls in the same direction as the water seal forced to swirl by the pressurized wash water discharging from the second means, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises fifth means for controlling the discharging of wash water from the second means and the discharging of wash water from the third means. 
   When the order, timing, combination, etc. of the discharging of wash water from the second means and the discharging of wash water from the third means are controlled appropriately, the time necessary for flushing the toilet body, the efficiency of flushing the toilet body, etc. can be optimized, and the quantity of wash water necessary for flushing the toilet body can be minimized. 
   In accordance with a preferred embodiment of the present invention, the fifth means controls the third means to discharge wash water after the pressurized wash water discharging from the second means reaches the water seal. 
   When the pressurized wash water reaches the water seal, the wash water entrains the water seal to swirl it, thereby forcing the water seal to flow into the trap-way. The wash water discharging from the third means entrains the water seal to force its flow into the trap-way. The pressurized wash water discharging from the second means and the wash water discharging from the third means entrain the water seal to promote its flow into the trap-way. Thus, the trap-way is filled up with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   In accordance with a preferred embodiment of the present invention, the fifth means controls the third means to discharge wash water after the second means finishes discharging the pressurized wash water. 
   It can be assumed that the pressurized wash water reaches the water seal before the second means finishes discharging the pressurized wash water. Therefore, when the third means discharges the wash water after the second means has finished discharging the wash water, the pressurized wash water discharging from the second means and the wash water discharging from the third means entrain the water seal to promote its flow into the trap-way. Thus, the trap-way is filled up with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   In accordance with a preferred embodiment of the present invention, the toilet body is made of ceramic and the second means comprises a nozzle mounted on the upper peripheral portion of the bowl. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises a pipe for leading the pressurized wash water to the nozzle. 
   When the pressurized wash water is led to a nozzle through a pipe to discharge from the nozzle, discharging direction of the wash water, discharging speed of the wash water, flow line of the discharging wash water and swirling flow of the wash water are stabilized and work for forming a wash water passage becomes easy. 
   In accordance with a preferred embodiment of the present invention, the quantity of wash water discharging from the toilet body when the toilet body is flushed is not more than 7 liters. 
   The swirling flow of the pressurized wash water discharging from the second means has large kinetic energy because it has high speed. The swirling flow of the pressurized wash water with large kinetic energy entrains the water seal to make it swirl at a high speed, thereby flushing the water seal and the soil promptly from the toilet body. Therefore, the toilet body can be flushed with 7 liters or less of the wash water. The water seal and the soil are entrained by not only the swirling flow of the pressurized wash water discharging from the second means but also the wash water discharging from the third means to be flushed from the toilet body promptly. Therefore, the toilet body can be flushed with 7 liters or less of the wash water. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises sixth means for mixing the pressurized wash water discharging from the second means with air. 
   A bubbly steam of wash water containing an abundance of micro air bubbles dispersed in the wash water does not splash or cause loud noise when it collides against a solid surface, while generates high frequency vibration when it collides against a solid surface to wash it strongly. Therefore, disposition of the means for mixing the pressurized wash water with air enhances the quietness and the detergency of the flush toilet. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises seventh means for controlling the flow rate of the pressurized wash water discharging from the second means. 
   It is possible to control the flow rate of the pressurized wash water to control the flow speed of the wash water, thereby controlling and optimizing the ratio of the mixed air to the wash water to generate a bubbly stream of wash water. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises an air intake pipe communicating with the sixth means at its one end and exposed to the atmosphere at its the other end. 
   Freedom in arranging an air intake increases by disposing an air intake pipe. Therefore, it becomes possible to arrange an air intake at a place shielded from the line of sight of a user of the flush toilet and free from splashed water. It becomes possible to keep noise generated in the sixth means apart from the user, thereby enhancing the quietness of the flush toilet. 
   In accordance with a preferred embodiment of the present invention, the air intake pipe comprises eighth means for discharging wash water flowing back from the sixth means. 
   When wash water flowing back from the sixth means is discharged from the air intake pipe, it becomes possible to mix wash water with air stably. Air flowing in the air intake pipe at high speed is prevented from contacting wash water to prevent generation of noise due to the contact of the air with the wash water. 
   In accordance with a preferred embodiment of the present invention, the other end of the air intake pipe exposed to the atmosphere opens in the inner surface of the bowl of the toilet body above the water seal. 
   When the other end of the air intake pipe exposed to the atmosphere opens in the inner surface of the bowl of the toilet body above the water seal, it becomes possible to discharge the wash water flowing back from the sixth means to the bowl. Therefore, it becomes possible to discharge the wash water to the bowl when the second means clogs. 
   In accordance with a preferred embodiment of the present invention, the sixth means comprises an exhaust nozzle for wash water, an air intake exposed to the atmosphere, an air contact chamber disposed downstream of and close to the exhaust nozzle, communicating with the air intake, storing sucked air temporarily, and making the wash water discharging from the exhaust nozzle contact the stored air, and an air mix chamber disposed downstream of the air contact chamber and mixing the wash water with the air. 
   Air passes through the air intake and flows into the air contact chamber, contacts wash water exhausting from the exhaust nozzle, is applied with friction force from the wash water, and is entrained by the wash water to flow into the air mix chamber. The wash water and the air are mixed with each other in the air mix chamber to generate a bubbly stream of wash water. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises ninth means for dispersing wash water exhausting from the exhaust nozzle in the air contact chamber. 
   When wash water exhausting from the exhaust nozzle disperses in the air contact chamber, the contact area between the wash water and air increases, the quantity of air entrained by the wash water to flow into the air mix chamber increases, the ratio of the mixed air to the wash water increases, and generation of a bubbly stream of wash water is promoted. When the wash water disperses, the air is mixed with the wash water uniformly, and the bubbly stream of wash water becomes more stable. When the wash water disperses, mixing of micro air bubbles with the wash water is promoted, and it becomes possible to generate the bubbly stream of wash water without using a device for breaking air bubbles. 
   In accordance with a preferred embodiment of the present invention, the ninth means generates turbulence in the wash water at the exhaust nozzle or at a position upstream of and close to the exhaust nozzle. 
   When the wash water becomes turbulent at the exhaust nozzle or at a position upstream of and close to the exhaust nozzle, the wash water exhausting from the exhausting nozzle into the air forms a turbulent flow structured by a main flow and branched flows having components of flow speed different from that of the main flow. The branched flows project from the surface of the main flow just after exhausting from the exhaust nozzle to be separated from the main flow due to surface tension and friction force applied by the air around the flows, thereby forming water drops and dispersing radially. 
   In accordance with a preferred embodiment of the present invention, the sectional areas of the air contact chamber and the wash water passage downstream of the air contact chamber are larger than that of the exhaust nozzle. 
   The wash water flows in the air contact chamber and the wash water passage downstream of the air contact chamber is mixed with air and apparent flow rate of the wash water increases. Therefore, the sectional areas of the air contact chamber and the wash water passage downstream of the air contact chamber should be larger than that of the exhaust nozzle. 
   In accordance with a preferred embodiment of the present invention, the air intake is connected to the air contact chamber through an air intake pipe. 
   Freedom in arranging the air intake increases owing to provision of the air intake pipe. Therefore, it becomes possible to arrange the air intake at a place shielded from the line of sight of a user of the flush toilet and free from splashed water. It becomes possible to keep noise generated in the sixth means apart from the user, thereby enhancing the quietness of the flush toilet. 
   In accordance with a preferred embodiment of the present invention, the air intake pipe comprises tenth means for discharging the wash water flowing back from the air contact chamber. 
   When the wash water flowing back from the air contact chamber is discharged from the air intake pipe, it becomes possible to mix the wash water with air stably. The air flowing in the air intake pipe at high speed is prevented from contacting the wash water to prevent generation of noise due to the contact of the air with the wash water. 
   In accordance with a preferred embodiment of the present invention, the air intake opens in the inner surface of the bowl of the toilet body above the water seal. 
   When the air intake opens in the inner surface of the bowl of the toilet body above the water seal, it becomes possible to discharge the wash water flowing back from the air contact chamber to the bowl. Therefore, it becomes possible to discharge the wash water to the bowl when the second means clogs. 
   In accordance with a preferred embodiment of the present invention, the air mix chamber is bent. 
   When the wash water collides against the bent portion of the air mix chamber, the flow speed of the wash water decreases. When the speed reduction of the wash water occurs steadily in the air mix chamber, the wash water is stored temporarily in the air mix chamber. Thus, mixing of the wash water with the air is promoted. When the wash water flowing into the air mix chamber from the air contact chamber collides against the wash water temporarily stored in the air mix chamber, the air bubbles dispersing in the wash water are further broken up, and the generation of the bubbly stream of wash water is further promoted. When the air mix chamber is bent by about 90 degrees, the temporary storage of the wash water in the air mix chamber and the discharge of the bubbly stream of wash water from the air mix chamber are optimized. 
   In accordance with a preferred embodiment of the present invention, the flush toilet further comprises eleventh means for rectifying the bubbly stream of wash water downstream of the air mix chamber. 
   When the eleventh means for rectifying the bubbly stream of wash water is disposed downstream of the air mix chamber, the bubbly stream of wash water is prevented from becoming turbulent and gas-liquid separation due to turbulent flow is prevented. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     In the drawings: 
       FIG. 1  is a partially cutaway plan view of a flush toilet in accordance with a first preferred embodiment of the present invention. 
       FIG. 2  is a sectional view taken along arrows  2 — 2  in FIG.  1 . 
       FIG. 3  is a sectional view taken along arrows  3 — 3  in FIG.  1 . 
       FIG. 4  is a block diagram of a valve unit. 
       FIG. 5  is a side sectional view of a rim water pipe. 
       FIG. 6  is a sectional view taken along arrows  6 — 6  in FIG.  5 . 
       FIG. 7  is a perspective view of a toilet body showing behavior of rim flush water. 
       FIG. 8  is a perspective view of a toilet body showing behavior of jet flush water. 
       FIG. 9  is a side sectional view of a valve controller in the valve unit. 
       FIG. 10  is a side sectional view of a pilot operated valve device provided for the valve unit. 
       FIG. 11  is a time chart showing the operation of the pilot valve in the pilot operated valve device, 
       FIG. 12  is a time chart of the flushing of the toilet body. 
       FIG. 13  is a partial side sectional view of a variation of the valve controller. 
       FIG. 14  is a partially cutaway plan view of a flush toilet in accordance with a second preferred embodiment of the present invention. 
       FIG. 15  is a sectional view taken along arrows  15 — 15  in FIG.  14 . 
       FIG. 16  is a partially cutaway plan view of a flush toilet in accordance with a third preferred embodiment of the present invention. 
       FIG. 17  is a side sectional view of a flush toilet in accordance with a fourth preferred embodiment of the present invention. 
       FIG. 18  is a perspective view of a flush toilet in accordance with a fifth preferred embodiment of the present invention. 
       FIG. 19  is a cross-sectional view of the upper end of a bowl of the flush toilet in FIG.  18 . 
       FIG. 20  is a structural view of a valve unit provided for the flush toilet in FIG.  18 . 
       FIG. 21  is a set of sectional views of an air mix device provided for the flush toilet in FIG.  18 . (a) is a side sectional view, (b) is a sectional view taken along arrows b—b in (a), and (c) is a sectional view taken along arrows c—c in (a). 
       FIG. 22  is a fragmentary enlarged detail of FIG.  21 . 
       FIG. 23  is a fragmentary side sectional view of the air mix device showing wash water dispersing in an air contact chamber. 
       FIG. 24  is a fragmentary side sectional view of the air mix device showing a bubbly stream of wash water generating in an air mix chamber. 
       FIG. 25  is a cross-sectional view of a variation of the flush toilet in accordance with the third preferred embodiment of the present invention. 
       FIG. 26  is a side-sectional view of a variation of a wash water dispersion device in the air mix device provided for the fifth preferred embodiment of the present invention. 
       FIG. 27  is a side-sectional view of a variation of a wash water dispersion device in the air mix device provided for the fifth preferred embodiment of the present invention. 
       FIG. 28  is a side-sectional view of a variation of a wash water dispersion device in the air mix device provided for the fifth preferred embodiment of the present invention. 
       FIG. 29  is a side-sectional view of a variation of a wash water dispersion device in the air mix device provided for the fifth preferred embodiment of the present invention. 
       FIG. 30  is a side-sectional view of a variation of a wash water dispersion device in the air mix device provided for the fifth preferred embodiment of the present invention. 
       FIG. 31  is a side-sectional view of a variation of a wash water dispersion device in the air mix device provided for the fifth preferred embodiment of the present invention. 
       FIG. 32  is a side-sectional view of a back flow prevention device which can be used in the air mix device provided for the fifth preferred embodiment of the present invention. 
       FIG. 33  is a fragmentary side-sectional view of a variation of the air mix device provided for the fifth preferred embodiment of the present invention. 
       FIG. 34  is a side-sectional view of an air mix device which can be used in any one of the flush toilets in accordance with the first preferred embodiment to the fourth preferred embodiment of the present invention. 
       FIG. 35  is a side-sectional view of an air mix device which can be used in any one of the flush toilets in accordance with the first preferred embodiment to the fourth preferred embodiment of the present invention. 
       FIG. 36  is a perspective view of a urinal to which the present invention is applied. 
       FIG. 37  is a sectional view taken along arrows  37 — 37  in FIG.  36 . 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   A flush toilet in accordance with a first preferred embodiment of the present invention will be described. 
   As shown in  FIGS. 1  to  3 , a flush toilet  100  in accordance with a first preferred embodiment of the present invention is provided with a toilet body  110  made of ceramic. The toilet body  110  is provided with a bowl  111 . The bowl  111  forms a wet surface  111   a  contacting water seal RW at the lower part of its inner surface and a dry surface  111   b  not contacting the water seal RW at the upper part of its inner surface. The dry surface  111   b  is provided with an annulus concave  111   c  at its upper peripheral portion. The annulus concave  111   c  extends substantially horizontally. The bowl  111  forms an annulus rim at its upper end. An overhang  111   d  extends from the annulus concave  111   c  to the annulus rim  112 . 
   The bowl  111  is provided with a concave  113  at its bottom. A trap-way  114  with reversed S shape extends rearward from a side of the concave  113 . The trap-way  114  is connected to a discharge pipe  130  at its downstream end through a socket  120 . 
   The toilet body  110  is provided with a housing  115  to the rear of the bowl  111  and on the annulus rim  112 . 
   A valve unit  140  is installed in the housing  115 . The valve unit  140  connects to a feed water pipe  150  extending from a pressurized water source such as a city water supply pipe, a tank set on the roof of a house or a building, a pump, etc. As shown in  FIG. 4 , the valve unit  140  is provided with a control button  16 , a valve controller  5  driven by the control button  16 , a switching valve device  25  driven by the valve controller  5 , and a selector valve device  26 . The switching valve device  25  and the selector valve device  26  collaborate to form a pilot operated valve device  21 . The switching valve device  25  connects to the feed water pipe  150 . The selector valve device  26  is disposed downstream of the switching valve device  25 . A rim water pipe  160  extends from the selector valve device  26  to the annulus concave  111   c  in the bowl  111  through a void space formed in the toilet body  110 . A jet water pipe  170  extends from the selector valve device  26  to the concave  113  in the bowl  111  through a void space formed in the toilet body  110 . As shown in  FIG. 3 , the control button  16  penetrates a cover  17  of the housing  115  and extends upward. 
   As shown in  FIGS. 5 and 6 , the rim water pipe  160  is provided with a straight pipe  161  extending into the housing  115  through an opening  115   a  formed in the bottom of the housing  115  to connect to the valve unit  140  at its one end, a bent pipe  162  connecting to the other end of the straight pipe  161  at its one end, and a straight pipe  163  connecting to the other end of the bent pipe  162  at its one end and projecting in the annulus concave  111   c  through an opening  111   e  formed in the bottom of the annulus concave  111   c  at its the other end. The straight pipes  161  and  163  are made of resin or metal, while the bent pipe  162  is made of flexible elastic material such as rubber, elastomer, soft resin, etc. The straight pipe  163  is provided with a grid like rectification disk  164  at its longitudinal middle and a flange  165  at a portion close to the other end. A nozzle  166  threads onto the other end of the straight pipe  163 . The flange  165  and the nozzle  166  collaborate to clamp a sidewall of the bowl  111  with a seal member  167  inserted between them. As seen from  FIGS. 1 and 3 , the nozzle  166  is directed in parallel with the longitudinal axis of the annulus concave  111   c  and so as to form an anticlockwise swirl flow of wash water as seen from the above. 
   The jet water pipe  170  is made of resin or metal. The jet water pipe  170  extends into the housing  115  through the opening  115   a  formed in the bottom of the housing  115  to connect to the valve unit  140  at its one end. The jet water pipe  170  connects to a jet discharge nozzle  113   a  formed in the side wall of the concave  113  at its the other end. The jet discharge nozzle  113   a  is disposed below a water plane WL of the water seal RW. The connection between the other end of the jet water pipe  170  and the jet discharge nozzle  113   a  is sealed with an appropriate seal member. As seen from  FIG. 1 , the jet discharge nozzle  113   a  is directed so as to form an anticlockwise swirl flow of wash water as seen from the above. 
   The operation of the flush toilet  100  will be described. 
   A user manipulates the control button  16  in the valve unit  140  to drive the valve controller  5 . The valve controller  5  drives the switching valve device  25  to open it. Pressurized wash water supplied from the pressurized water source such as a city water supply pipe, a tank set on the roof of a house or a building, a pump, etc. passes through the feed water pipe  150  and the switching valve device  25  to reach the selector valve device  26 . 
   The valve controller  5  drives the selector valve device  26  to make the pressurized wash water flow into the rim water pipe  160 . The pressurized wash water is passed through the rim water pipe  160 , rectified with the rectification disk  164 , and discharges into and in parallel with the annulus concave  111   c  from the nozzle  166 . The pressurized wash water discharging from the nozzle  166  forms rim flush water RS as indicated by void arrows in FIG.  7 . The rim flush water RS flows anticlockwise as seen from the above along the annulus concave  111   c  as indicated void arrows in  FIG. 7 , flows out the annulus concave  111   c  downward, flows gradually downward along the dry surface  111   b , while branching into a plurality of branched flows, goes once or more round the dry surface  111   b  including the annulus concave  111   c , and then reaches the water seal RW. The rim flush water RS flushes soil adhering to the dry surface  111   b . The rim flush water RS joins with the water seal RW to drive it, thereby swirling it anticlockwise. The swirling water seal RW flows into the trap-way  114  extending from the side of the concave  113  with soil. 
   After the rim flush water RS reaches the water seal RW, the valve controller  5  drives the selector valve device  26  to stop the flow of the pressurized wash water into the rim water pipe  160  and lead the pressurized wash water into the jet water pipe  170 . The pressurized wash water passes through the jet water pipe  170  and discharges into the concave  113  from the jet discharge nozzle  113   a . The pressurized wash water discharging from the jet discharge nozzle  113   a  form jet flush water BS as indicated by void arrows in  FIGS. 7 and 8 . The jet flush water BS flows along the sidewall of the concave  113   a  to form a flow swirling anticlockwise as seen from the above. The swirling jet flush water BS not only flows into the trap-way  114  extending from the side of the concave  113  but also entrains the water seal RW swirling in the same direction to make it flow into the trap-way  114 . 
   The water seal RW with which the rim flush water RS joins and the jet flush water BS flow into the trap-way  114 , the trap-way  114  is filled the with wash water, a siphon phenomenon appears, and soil in the bowl  111  are discharged from the trap-way  114  to the discharge pipe  130  promptly. 
   After the bowl  111  becomes empty, the valve controller  5  drives the selector valve device  26  to stop the flow of the pressurized wash water into the jet water pipe  170  and lead the pressurized wash water into the rim water pipe  160 . The rim flush water RS discharging from the nozzle  166  forms the water seal RW in the bowl  111 . 
   After the water seal RW forms, the valve controller  5  stops the operation of the switching valve device  25  to close the switching valve device  25 . The flow of the pressurized wash water into the bowl  111  stops and the flushing of the toilet body is completed. 
   The flush toilet  100  does not cause loud noise during its operation because the rim flush water RS swirls and goes down along the dry surface  111   b  to run into the water seal RW aslant. The rim flush water RS is pressurized wash water with water pressure higher than that of the wash water with about 250 mm of water head led from a tank directly connected to the toilet body. Therefore, the rim flush water RS swirls along the dry surface  111   b  at high speed to achieve a strong detergency against the dry surface  111   b . The rim flush water swirling along the dry surface  111   b  by 360 degrees or more dwells on the dry surface  111   b  for a long time to achieve a strong detergency against the dry surface  111   b.    
   The overhang  111   d  prevents the rim flush water RS discharging substantially horizontally from the nozzle  166  from running out the bowl  111  beyond the rim  112 . 
   The trap-way  114  enables flushing of soil out the toilet body  110  to enhance the efficiency of flushing soil. The jet flush water BS discharging from the jet discharge nozzle  113   a  is swirled and directed to the inlet of the trap-way  114  formed in the side of the concave  113 . Thus, the trap-way  114  is filled up with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   When pressurized wash water discharges from the jet discharge nozzle  113   a , the jet flush water BS flows into the trap-way  114  at high speed, and the quantity of the water seal RW entrained by the jet flush water BS to flow into the trap-way  114  increases. Thus, the trap-way  114  is filled up with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   The jet flush water BS discharging below the water plane WL of the water seal RW forces the soil depositing on the concave  113  directly into the trap-way  114  to enhance the efficiency of flushing soil. 
   The jet flush water BS swirls in the same direction as the water seal RW to increase the flow rate of the water seal RW entrained by the jet flush water BS and flowing into the trap-way  114 . Thus, the trap-way  114  is filled with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   When the order, timing, combination, etc. of the rim flush water RS discharging from the nozzle  166  and the jet flush water BS discharging from the jet discharge nozzle  113   a  are controlled appropriately with the valve unit  140 , the time necessary for flushing the toilet body, the efficiency of flushing the toilet body, etc. are optimized, and the quantity of wash water necessary for flushing the toilet body is minimized. 
   When the rim flush water RS reaches the water seal RW, the rim flush water RS entrains the water seal RW to swirl it, thereby forcing the water seal RW to flow into the trap-way  114 . The jet flush water RS discharges after the rim flush water RS reaches the water seal RW to entrain the water seal RW, thereby forcing it to flow into the trap-way  114 . The rim flush water RS and the jet flush water BS entrain the water seal RW to promote its flow into the trap-way  114 . Thus, the trap-way  114  is filled up with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   The size of the outlet, shape, surface roughness, etc. of the nozzle  166  can be optimized easily. Longitudinal distribution of diameter, distribution of surface roughness of the inner surface, etc. of the rim water pipe  160  can be optimized easily. Therefore, when the pressurized wash water is led to the nozzle  166  through the rim water pipe  160  and the rectification disk  164  disposed midway of the rim water pipe  160 , the discharging direction, discharging speed, flow line and swirling flow of the rim flush water RS are stabilized easily. The rim water pipe  160  can contribute to easy formation of a wash water passage better than a water passage integrally formed in the toilet body  110 . 
   The swirling flow of the rim flush water RS made of pressurized wash water has large kinetic energy because it has high speed. The swirling flow of the rim flush water RS with large kinetic energy entrains the water seal RW to make it swirl at high speed. Thus, the water seal RW flows into the trap-way  114  with soil promptly to be flushed from the toilet body  110 . Therefore, the toilet body of the flush toilet  100  can be flushed with 7 liters or less of the wash water. The water seal RW and the soil are entrained by not only the swirling flow of the rim flush water RS made of the pressurized wash water but also the jet flush water BS to be promptly flushed from the toilet body  110 . Therefore, the toilet body of the flush toilet  100  can be flushed with 7 liters or less of the wash water. 
   The structure of the valve unit  140  will be described in detail. 
   As shown in FIG.  9 ( a ), the valve control device  5  in the valve unit  140  is provided with a mechanical timer A which also serves as a driving device, and a valve switching device B. The valve switching device B engages the control button  16  penetrating the cover  17  of the housing  115 . 
   The mechanical timer A is provided with a cylinder  6 . The cylinder  6  is provided with a circumferential wall  6   a  and end walls  6   b  and  6   c . The end wall  6   b  is provided with an air hole  6   d . The end wall  6   c  is provided with an orifice  7 . 
   A piston  8  is inserted in the cylinder  6 . The piston  8  is provided with a piston rod  8   a  and a piston head  8   b . The piston rod  8   a  penetrates the end wall  6   b  to slide. The piston head  8   b  abuts against the inner surface of the circumferential wall  6   a  of the cylinder to slide. The abutment is sealed with an O-ring  9 . The O-ring  9  is received in a groove  8   b   1  formed in the circumferential surface of the piston head  8   b . A side wall of the groove  8   b   1  opposite the end wall  6   b  of the cylinder  6  is cut out partially over an appropriate length. A chamber α is formed between the piston head  8   b  and the end wall  6   b  and a chamber β is formed between the piston head  8   b  and the end wall  6   c . A coil spring  10  is disposed in the chamber β. 
   The valve switching device B is provided with a spindle  11 . The spindle  11  abuts against the free end of the piston rod  8   a  at its one end. The spindle  11  is inserted in a guide hole formed in a guide member  12  to be movable in the longitudinal direction. The spindle  11  is provided with a cam  11   a  on its one side surface. The cam  11   a  is provided with a slope  11   a   1  adapted to increase the diameter of the spindle  11  from one end abutting against the free end of the piston rod  8   a  toward the other end and a straight surface  11   a   2  connecting to the end of the slope  11   a   1 . 
   The spindle  11  is provided with a concave  11   b  on its the other side surface. A surface of the concave  11   b  crossing at right angles with the longitudinal axis of the spindle  11  forms a cam  11   c . A cam engaging member  13  is disposed in the concave  11   b . The cam engaging member  13  is connected to the spindle  11  to swing between a first position indicated by a solid line in FIG.  9 ( a ) where the cam engaging member  13  abuts against the cam lie to project outward radially from the spindle  11  at its one end and a second position indicated by a phantom line in FIG.  9 ( a ) where the cam engaging member  13  leaves the cam  11   c  to be received in the concave  11   b  as a whole. The cam engaging member  13  stays at the first position under a force of a weak return spring  13   a  when no load is applied to the cam engaging member  13 . 
   A cam rod  14  is disposed opposite the cam  11   a  of the spindle  11  and at right angles to the longitudinal axis of the spindle  11 . A cam rod  15  is disposed opposite the cam engaging member  13  and at right angles to the longitudinal axis of the spindle  11 . The cam rod  14  is connected to the switching valve device  25 . The cam rod  15  is connected to the selector valve device  26 . 
   The control button  16  is inserted in a guide hole formed in the cover  17  of the housing  115  to move in the longitudinal direction. The control button  16  abuts against the other end of the spindle  11  at its one end extending into the housing  115 . 
   As shown in  FIG. 10 , a pilot operated valve device  21  is provided with an inlet  22  of the wash water, an outlet  23  of the wash water for rim discharging, an outlet  24  of the wash water for jet discharging, a switching valve device  25  and a selector valve device  26 . The inlet  22  is connected to the feed water pipe  150 . The outlet  23  is connected to the rim water pipe  160 . The outlet  24  is connected to the jet water pipe  170 . 
   The switching valve device  25  is provided with a diaphragm valve  254  structured by a diaphragm  251 , a valve seat  252  and a biasing spring  253 , and a wash water passage  255  switched by the diaphragm valve  254 . The wash water passage  255  communicates with the inlet  22  through a flow regulating valve  27  and communicates with the chamber  28  when the diaphragm valve  254  opens. 
   The switching valve device  25  is provided with a pressure chamber  256 . The diaphragm  251  forms a part of the enclosure of the pressure chamber  256 . The diaphragm  251  is provided with a pilot inlet passage  257  communicating with the pressure chamber  256 . A pilot outlet passage  258  extends from the pressure chamber  256 . A pilot valve  259  for switching the pilot outlet passage  258  is disposed. The pilot valve  259  is provided with a valve body and a coil spring for forcing the valve body to close the pilot outlet passage  258 . The valve body and the coil spring are not shown in Figures. The cam rod  14  is fixed to the valve body. The cam rod  14  is driven by the valve controller  5  shown in FIG.  9 . 
   The selector valve device  26  is provided with a diaphragm valve  264  structured by a diaphragm  261 , a valve seat  262  and a biasing spring  263 , and a wash water passage  265  switched by the diaphragm valve  264 . The wash water passage  265  communicates with a chamber  28  and communicates with the outlet  24  when the diaphragm valve  264  opens. 
   The selector valve device  26  is provided with a pressure chamber  266 . The diaphragm  261  forms a part of the enclosure of the pressure chamber  266 . The diaphragm  261  is provided with a pilot inlet passage  267  communicating with the pressure chamber  266 . A pilot outlet passage  268  extends from the pressure chamber  266 . A pilot valve  269  for switching the pilot outlet passage  268  is provided. The pilot valve  269  is provided with a valve body and a coil spring for forcing the valve body to close the pilot outlet passage  268 . The valve body and the coil spring are not shown in Figures. The cam rod  15  is fixed to the valve body. The cam rod  15  is driven by the valve controller  5  shown in FIG.  9 . 
   A diaphragm valve  29  is disposed between the chamber  28  and the outlet  23 . The diaphragm valve  29  is structured by a diaphragm  291 , a valve seat  292  and a biasing spring  293 . A pressure chamber  294  is disposed. The diaphragm  291  forms a part of the enclosure of the pressure chamber  294 . The pressure chamber  294  communicates with the outlet  24  through a communicating hole  295  downstream of the diaphragm valve  264 . 
   The operation of the valve controller  5  and the pilot operated valve device  21  will be described. 
   When the flush toilet is not being used, the valve controller  5  is in the initial condition shown in FIG.  9 ( a ). The control button  16  is located at a start point shown in FIG.  9 ( a ) and projects from the cover  17 . The spindle  11  of the valve switching device B is located at a start point and projects from the guide member  12 . The cam engaging member  13  is located at the first position. The cam rod  14  is located between the cam  11   a  and the end wall  6   b  of the cylinder  6 . The cam rod  15  is located between the cam engaging member  13  and the end wall  6   b  of the cylinder  6 . 
   When the valve controller  5  is in the initial condition shown in FIG.  9 ( a ), the valve body of the pilot valve  259  is forced by the coil spring in the direction for closing the pilot outlet passage  258  and the pilot valve  259  closes the pilot outlet passage  258 . Thus, the wash water is prevented from entering into the pressure chamber  256 . The upstream pressure of the diaphragm valve  254  is substantially the same as that in the pressure chamber  256  due to the pilot inlet passage  257 . The force applied to the diaphragm  251  by the pressure in the pressure chamber  256  is larger than that by the pressure in the wash water passage  255  because the downstream pressure of the diaphragm valve  254  is lower than the upstream pressure of the diaphragm valve  254 . The diaphragm  251  is forced by the spring  253 . Therefore, the diaphragm  251  is forced against the valve seat  252 , the diaphragm valve  254  or the switching valve device  25  closes the wash water passage  255 , the rim flush water RS is not discharged from the nozzle  166 , and the jet flush water BS is not discharged from the jet discharge nozzle  113   a.    
   When the valve controller  5  is in the initial condition shown in FIG.  9 ( a ), the valve body of the pilot valve  269  is forced by the coil spring in the direction for closing the pilot outlet passage  268  and the pilot valve  269  closes the pilot outlet passage  268 . Thus, the wash water is prevented from entering into the pressure chamber  266 . The diaphragm valve  264  or the selector valve device  26  closes the wash water passage  265  in the same way as the switching valve device  25 . 
   When the valve controller  5  is in the initial condition shown in FIG.  9 ( a ), the diaphragm  291  abuts the valve seat  292  under the biasing force of the spring  293 . Thus, the diaphragm valve  29  intercepts the communication between the chamber  28  and the outlet  23 . 
   A user of the flush toilet manually pushes the control button  16 , the control button  16  starts to move toward the guide member  12 , the spindle  11  starts outward movement from the start point toward the cylinder  6 , and the piston head  8   b  starts to move in the cylinder  6  toward the end wall  6   c , while compressing the coil spring  10 . 
   As indicated by two-dot chain lines in FIG.  9 ( a ), the O-ring  9  is exposed to a friction force from the circumferential wall  6   a  of the cylinder  6  to be extruded partially from the groove  8   b   1  through the cutout formed in the side wall of the groove  8   b   1 . Thus, the seal by the O-ring  9  is broken. Air in the chamber β with its volume decreasing flows into the chamber a with its volume increasing through a space between the piston head  8   b  and the circumferential wall  6   a  of the cylinder  6 . Air flows into the chamber α with its volume increasing through the air hole  6   d  formed in the end wall  6   b  of the cylinder  6 . 
   The cam  11   a  of the spindle  11  engages the cam rod  14  to drive the cam rod  14  in the direction indicated by a void arrow in FIG.  9 ( a ) away from the spindle  11 . The cam  11   a  drives the valve body of the pilot valve  259  in the switching valve device  25  in the direction for opening the pilot outlet passage against the biasing force of the coil spring. Thus, the pilot valve  259  opens the pilot outlet passage  258 . When the pilot outlet passage  258  opens, the wash water flows into the pressure chamber  256  through the pilot inlet passage  257  and flows out the pressure chamber  256  through the pilot outlet passage  258 . The aforementioned operations are caused immediately after pushing the control button  16 . Therefore, the pilot valve  259  opens as shown in  FIG. 11 , simultaneously with the start of flushing due to pushing the control button  16 . 
   The pressure in the pressure chamber  256  becomes lower than the upstream pressure of the diaphragm valve  254  due to the pressure loss generated when the wash water passes through the pilot inlet passage  257  with small diameter. The forces acting on the diaphragm  251  are thrown out of balance and the diaphragm  251  leaves the valve seat  252  to move toward the pressure chamber  256 . Thus, the diaphragm valve  254  or the switching valve device  25  opens the wash water passage  255 . 
   The wash water passes through the inlet  22 . The flow rate of the wash water is adjusted to a predetermined valve Q by the flow regulating valve  27 . The wash water flows into the chamber  28  through the wash water passage  255 . The pressure in the chamber  28  increases, the forces acting on the diaphragm  291  are thrown out of balance, and the diaphragm  291  leaves the valve seat  292  to move toward the pressure chamber  294 . Thus, the diaphragm valve  29  communicates the chamber  28  with the outlet  23 . When the chamber  28  communicates with the outlet  23 , the wash water discharges from the outlet  23 . The wash water discharging from the outlet  23  at flow rate Q passes through the rim water pipe  160  to discharge from the nozzle  166 , thereby forming the rim flush water RS. The rim flush water RS carries out an initial rim flushing as shown in FIG.  12 . During the initial rim flushing, the swirling flow of the pressurized wash water washes the dry surface  111   b  of the inner surface of the bowl strongly as aforementioned. 
   When the cam engaging member  13  contacts the cam rod  15 , it swings from the first position to the second position under a load applied by the cam rod  15 . Therefore, the cam  11   c  does not engage the cam rod  15  through the cam engaging member  13  and does not drive the valve body of the pilot valve  269  through the cam engaging member  13  and the cam rod  15 . Therefore, the pilot valve  269  closes the pilot outlet passage  268 , and the pilot valve  264  in the selector valve device  26  closes the wash water passage  265 . Thus, the chamber  28  does not communicate with the outlet  24  and the jet flush water BS does not discharge from the jet discharge nozzle  113   a.    
   As shown in FIG.  9 ( b ), the control button  16  abuts against the guide member  12  to stop moving, the spindle  11  reaches the end point to stop moving, thereby finishing the manipulation to start flushing. When the manipulation to start flushing the toilet body is finished, the cam engaging member  13  is released from engaging the cam rod  15 , and the cam engaging member  13  returns to the first position under the biasing force of the return spring  13   a.    
   When the user of the flush toilet removes his or her hand from the control button  16 , the piston head  8   b  starts to move toward the end wall  6   b  of the cylinder  6  as indicated by a void arrow in FIG.  9 ( b ), the spindle  11  starts homeward movement from the end point to the start point, and the control button  16  starts to move away from the guide member  12  under the biasing force of the coil spring  10 . The O-ring  9  is exposed to a friction force from the circumferential wall  6   a  of the cylinder  6  to return into the groove  8   b   1  through the cutout formed in the side wall of the groove  8   b   1 . Thus, the seal by the O-ring  9  is restored. Air flows into the chamber β with its volume increasing through the orifice  7  and air flows out the chamber α with its volume decreasing through the air hole  6   d . A part of the strain energy released from the coil spring  10  is consumed to become the heat when the air passes through the orifice  7 . The increase rate of the volume of the chamber β and the speed of the homeward movement of the spindle  11  are regulated by the flow rate of the air passing through the orifice  7 . The flow rate of the air passing through the orifice  7  is regulated by the spring constant of the coil spring  10  and the diameter of the orifice  7 . The spindle  11  moves homeward at substantially constant speed determined by the spring constant of the coil spring  10  and the diameter of the orifice  7 . 
   When the spindle  11  moves from the end point to the start point by a predetermined distance, or when a predetermined length of time elapses from the finish of the manipulation for starting the flushing, the cam engaging member  13  abuts against the cam rod  15  as shown in FIG.  9 ( c ). Though a load is applied to the cam engaging member  13  by the cam rod  15 , the cam engaging member  13  is only forced against the cam  11   c  and does not swing because the cam engaging member  13  is already returned to the first position under the biasing force of the return spring  13   a . Therefore, the cam  11   c  engages the cam rod  15  through the cam engaging member  13  to drive the cam rod  15 , and drive the valve body of the pilot valve  269  in the selector valve device  26  in the direction for opening the pilot outlet passage against the biasing force of the coil spring. Thus, the pilot valve  269  opens the pilot outlet passage  268  as shown in FIG.  11 . When the pilot outlet passage  268  opens, the wash water flows into the pressure chamber  266  through the pilot inlet passage  267  and flows out the pressure chamber  266  through the pilot outlet passage  268 . 
   The pressure in the pressure chamber  266  becomes lower than the upstream pressure of the diaphragm valve  264  due to the pressure loss generated when the wash water passes through the pilot inlet passage  267 . The forces acting on the diaphragm  261  are thrown out of balance and the diaphragm  261  leaves the valve seat  262  to move toward the pressure chamber  266 . Thus, the diaphragm valve  264  of the selector valve device  26  opens the wash water passage  265 . 
   The wash water flows into the wash water passage  265  from the chamber  28  and discharges from the outlet  24 . The wash water discharging from the outlet  24  at flow rate Q passes through the jet water pipe  170  to discharge from the jet discharge nozzle  113   a . The jet flush water BS discharging from the jet discharge nozzle  113   a  carries out a jet flushing as shown in FIG.  12 . The swirling jet flush water BS generates a siphon phenomenon in the trap-way  114  to discharge soil from the toilet body  110  promptly. 
   When the wash water flows to the outlet  24  through the opened wash water passage  265 , a part of the wash water enters into the pressure chamber  294 . Thus, the pressure in the pressure chamber  294  increases, the forces acting on the diaphragm  291  are thrown out of balance, and the diaphragm  291  is forced against the valve seat  292 . Thus, the diaphragm valve  29  intercepts the communication between the chamber  28  and the outlet  23 . Therefore, the wash water does not discharge from the nozzle  166  and the rim flushing is not carried out as shown in FIG.  12 . 
   When the spindle  11  moves further from the position shown in FIG.  9 ( c ) toward the start point, or when a predetermined length of time elapses from the point of time shown in FIG.  9 ( c ), the cam  11   c  is released from engaging the cam rod  15  through the cam engaging member  13  as shown in FIG.  9 ( d ). The valve body of the pilot valve  269  is released from the load by the cam rod  15  to move in the direction for closing the pilot outlet passage. Thus, the pilot valve  269  closes the pilot outlet passage  268  as shown in FIG.  11 . The diaphragm valve  264  or the selector valve device  26  closes the wash water passage  265 . The wash water stops discharging from the outlet  24 , the jet flush water BS stops discharging from the jet discharge nozzle  113   a , and the jet flushing is completed as shown in FIG.  12 . 
   The wash water stops flowing to the outlet  24  from the wash water passage  265 , the wash water flows out the pressure chamber  294  through the communication hole  295  to decrease the pressure in the pressure chamber  294 , forces acting on the diaphragm  291  are thrown out of balance, the diaphragm  291  leaves the valve seat  292  to move toward the pressure chamber  294 , and the diaphragm valve  29  communicates the chamber  28  with the outlet  23 . The wash water discharges from the outlet  23 . The wash water discharging from the outlet  23  at flow rate Q discharges from the nozzle  166 . The rim flush water RS discharging from the nozzle  166  carries out a rim flushing for forming water seal as shown in FIG.  12 . Thus, the water seal RW is formed in the bowl  110 . 
   When a predetermined length of time elapses from the point of time shown in FIG.  9 ( d ), the control button  16  returns to the start point where it projects from the cover  17  of the housing  115  and stops moving. The cam  11   a  is released from engaging the cam rod  14 , the valve body of the pilot valve  259  moves in the direction for closing the valve under the biasing force of the coil spring, and the pilot valve  259  closes the pilot outlet passage  258  as shown in FIG.  11 . The diaphragm valve  254  or the switching valve device  25  closes the wash water passage  255 . Thus, the wash water stops discharging from the pilot operated valve device  21 , the rim flushing for forming water seal is finished as shown in  FIG. 12 , and the flushing of the toilet body is finished. 
   It is possible to adjust the spring constant of the coil spring  10 , diameter of the orifice  7 , etc., thereby adjusting the speed of the homeward movement of the spindle  11 , adjust the stroke of the homeward movement of the spindle  11  in the initial rim flushing, adjust the stroke of the homeward movement of the spindle  11  in the jet flushing, and adjust the stroke of the homeward movement of the spindle  11  in the rim flushing for forming water seal, thereby adjusting the duration of the initial rim flushing, the duration of the jet flushing and the duration of the rim flushing for forming water seal as shown in FIG.  12 . The quantity of wash water used in each flushing can be adjusted by adjusting duration of each flushing because the flow rate of wash water in each flushing is kept constant, i.e. Q. Therefore, the quantity of discharging wash water in the initial rim flushing can be set at about 2 to 4 liters, the quantity of discharging wash water in the jet flushing can be set at about 3 liters, and the quantity of wash water discharged from the toilet body  110  in the flushing of the toilet body can be set at about 5 to 7 liters. The wash water discharging in the rim flushing for forming water seal is stored as water seal RW and not discharged from the toilet body  110 . 
   The toilet body can be flushed even at an electric service interruption because the mechanical timer A drives the valve switching device B to control the switching valve device  25  and the selector valve device  26 . The structure of the valve switching device B reciprocally moving to switch valves is simple. Thus, the structure of the valve controller  5  becomes simple. The mechanical timer A can be started by a single manipulation of pushing the control button  16  to the stop position. 
   In the pilot operated valve device  21 , the pilot valves  259  and  269  are switched so that the switching valve device  25  switches the wash water passage and the selector valve device  26  selects one from a plurality of wash water passages. The pilot outlet passages  258  and  268  operate even though their diameters are small. Therefore, small valves needing small forces for driving them can be used as the pilot valves  259  and  269 . Therefore, the forces applied to the cam rods  14  and  15  can be reduced and the valve controller  5  can be downsized. The force necessary for manipulating the control button  16  also can be reduced. When the pilot operated valve device  21  is used, the valve unit  40  is downsized, the housing  115  is downsized, and the toilet body  110  is downsized. 
   The flow rate of wash water in the initial rim flushing, the jet flushing and the rim flushing for forming water seal is regulated to Q with the flow regulating valve  27 . Thus, no water hammer is caused when the selection of the wash water passage is carried out. Therefore, the pilot operated valve device  21  can be downsized and lightened, and the production cost of the pilot operated valve device can be reduced because the pressure resistance of the members in the pilot operated valve device  21  need not be excessively large. 
   Variations of the valve switching device B will be described. 
   It is possible, as shown in FIG.  13 ( a ), to provide the control button  16  with a projection  16   b , engage the control button  16  with the cover  17  to rotate around a longitudinal axis of the control button  16 , and provide the spindle  11  with a step  11   d  at its one end. When the valve controller  5  is in the initial condition, the control button  16  in a predetermined rotational region abuts the said one end of the spindle  11  at the projection  16   b , but the control button  16  out of the predetermined rotational region is distanced from the said one end of the spindle  11 . Thus, the stroke of the outward movement of the spindle  11  in the case where the control button  16  is rotated to a predetermined rotational point and pushed in the cover  17  becomes different from the stroke of the outward movement of the spindle  11  in the case where the control button  16  is pushed in the cover  17  without being rotated to the predetermined rotational point. Thus, the quantity of discharging wash water in the case where the control button  16  is rotated to a predetermined rotational point and pushed in the cover  17  becomes different from the quantity of discharging wash water in the case where the control button  16  is pushed in the cover  17  without being rotated to the predetermined rotational point. Thus, the quantity of discharging wash water in flushing the toilet body after defecating can be made different from the quantity of discharging wash water in flushing the toilet body after urinating with a simple device and wash water used for flushing the toilet body can be saved. 
   It is possible, as shown in FIG.  13 ( b ), to divide the control button  16  into half portions  16 ′ and  16 ″, and provide the half portion  16 ′ with a projection  16   b ′. In this case, the stroke of the movement of the half portion  16 ′ when the half portion  16 ′ is pushed in the cover  17  becomes different from the stroke of the movement of the half portion  16 ″ when the half portion  16 ″ is pushed in the cover  17 , the stroke of the outward movement of the spindle  11  when the half portion  16 ′ is pushed in the cover  17  becomes different from the stroke of the outward movement of the spindle  11  when the half portion  16 ″ is pushed in the cover  17 . Thus, the quantity of discharging wash water when the half portion  16 ′ is pushed in the cover  17  becomes different from the quantity of discharging wash water when the half portion  16 ″ is pushed in the cover  17 . Thus, the quantity of discharging wash water in flushing the toilet body after defecating can be made different from the quantity of discharging wash water in flushing the toilet body after urinating with a simple device and wash water used for flushing the toilet body can be saved. The quantity of discharging wash water in flushing the toilet body after defecating can be made different from the quantity of discharging wash water in flushing the toilet body after urinating only by manipulating the desirable half portion  16 ′ or  16 ″. Thus, the flush toilet becomes more convenient. 
   A second preferred embodiment of the present invention will be described. 
   As shown in  FIGS. 14 and 15 , in a flush toilet  100 A in accordance with the present preferred embodiment, the rim  112  of the toilet body  110  is provided with a rim water passage  112   a  over a half round. The rim water passage  112   a  is provided with a rim discharge hole  112   b  directed aslant downward and toward the trap-way  114  at its end distanced from the housing  115 . The rim water passage  112   a  is provided with a rim discharge hole  112   c  at its end close to the housing  115 . A second rim water pipe  180  extends from the selector valve device  26  in the valve unit  140  instead of the jet water pipe  170  in the first preferred embodiment. The second rim water pipe  180  is provided with a nozzle  181  at its downstream end. The nozzle  181  is inserted in the rim discharge hole  112   c . An appropriate seal member is inserted in the space between the second rim water pipe and the rim discharge hole. In the present embodiment, the jet water pipe  170  and the jet discharge nozzle  113   a  are not disposed. The flush toilet  100 A has the same structure as the flush toilet  100  except for the aforementioned points. 
   In the flush toilet  100 A, second rim flush water RBS discharges through the second rim water pipe  180 , the rim water passage  112   a  and the rim discharge hole  112   b . The second rim flush water RBS flows down straight along the dry surface  111   b  of the bowl  111  as indicated by void arrows to reach the water seal RW, entrains the water seal RW and soil, flows down straight along the wet surface  111   a , and flows into the trap-way  114 . Thus, a siphon phenomenon appears to discharge soil from the toilet body promptly. 
   A third preferred embodiment of the present invention will be described. 
   As shown in  FIG. 16 , a flush toilet  100 B in accordance with the present preferred embodiment is not provided with a jet water pipe and a jet discharge nozzle. The valve unit  140  is not provided with a selector valve device and a device for driving the selector valve device. The flush toilet  100 B has the same structure as the flush toilet  100  except for the aforementioned points. 
   In the flush toilet  100 B, the toilet body is flushed only by the rim flush water discharging from the nozzle  166 . The pressurized rim flush water swirls and flows down along the dry surface  111   b  to wash the dry surface  111   b  strongly without causing loud noise. 
   A fourth preferred embodiment of the present invention will be described. 
   As shown in  FIG. 17 , a flush toilet  100 C in accordance with the present preferred embodiment is provided with a passage  116  at its fore portion. Wash water falls down through the passage  116 . The flush toilet  100 C is not provided with a trap-way, jet water pipe and jet discharge nozzle. The valve unit  140  is not provided with a selector valve device and device for driving the selector valve device. The flush toilet  100 C has the same structure as the flush toilet  100  except for aforementioned points. 
   In the flush toilet  100 C, the toilet body is flushed only by the rim flush water discharging from the nozzle  166 . The pressurized rim flush water swirls and flows down along the dry surface  111   b  to wash the dry surface  111   b  strongly without causing loud noise. Soil in the concave  113  is discharged from the toilet body  110  through the passage  116 . 
   A fifth preferred embodiment of the present invention will be described. 
   As shown in  FIGS. 18 and 19 , a flush toilet  200  in accordance with the present preferred embodiment is provided with a toilet body  210  made of ceramic. The toilet body  210  is provided with a bowl  211 . The bowl  211  forms a wet surface  211   a  contacting water seal RW at the lower part of its inner surface and a dry surface  211   b  not contacting the water seal RW at the upper part of its inner surface. The dry surface  211   b  is provided with an annulus bent  211   c  at its upper peripheral portion. The annulus bent  211   c  extends substantially horizontally. The bowl  211  forms an annulus rim  212  at its upper end. An overhang  211   d  extends from the annulus bent  211   c  to the annulus rim  212 . The annulus bent  211   c  is provided with a wash water discharge hole  211   e  directed in parallel with the longitudinal axis of the annulus bent  211   c.    
   A trap-way  214  with reversed S shape extends rearward from the bottom  213  of the bowl  211 . The trap-way  214  is connected to a discharge pipe with a socket at its downstream end. The socket is not shown in Figures. 
   The toilet body  210  is provided with a housing  215  to the rear of the bowl  211 . 
   A valve unit  240  is installed in the housing  215 . The valve unit  240  connects to a feed water pipe  250 . The feed water pipe  250  connects to a pressurized water source such as a city water supply pipe, a tank set on the roof of a house or a building, a pump, etc. through a stop valve  260 . 
   As shown in  FIG. 20 , the valve unit  240  is provided with an electromagnetic valve  241 , a flow regulating valve  242 , an internal connection pipe  243  and a manipulation device  244  for controlling the electromagnetic valve  241 . They are disposed in series in the said order from upstream to downstream in relation to wash water flow. The electromagnetic valve  242  connects to the feed water pipe  250 . 
   An air mix device  270  which also serves as a wash water passage extends from the valve unit  240 . As shown in  FIG. 21 , the air mix device  270  is provided with a connection hole  271 , an elbow  272 , a straight exhaust nozzle  273  with appropriate length and a diameter smaller than that of the elbow  272 , a straight air contact chamber  274  with large length and a diameter larger than that of the exhaust nozzle  273 , a straight check chamber  275  for preventing back flow with a diameter larger than that of the air contact chamber  274 , an air mix chamber  276  formed by an elbow with a diameter smaller than that of the check chamber  275 , a straight rectification chamber  277  with a diameter equal to that of the air mix chamber  276  and a flexible straight connection pipe  278 . They are disposed in series in the said order from upstream to downstream in relation to wash water flow. An air intake pipe  279  bent at right angles extends from the upstream end of he air contact chamber  275  beneath the exhaust nozzle  273 . The exhaust nozzle  273 , the air contact chamber  274  and the check chamber  275  extend substantially vertically, while the rectification chamber  277  and the connection pipe  278  extend substantially horizontally. An open end directed upward of the air intake pipe  279  forms an air intake  279   a . The check chamber  275  is provided with a step at its upstream end. The step forms a barrier  275   a  for preventing back flow. The rectification chamber  277  is provided with rectification fins  277   a . A fixing pipe  278   a  fits in the downstream end of the connection pipe  278 . The fixing pipe  278   a  is provided with rectification fins  278   b . The connection hole  271  is connected to an internal connection pipe  243  of the valve unit  240 . 
   As shown in  FIG. 22 , the fixing pipe  278   a  is provided with a flange  278   c  at its downstream portion. The fixing pipe  278   a  is also provided with a plurality of ribs  278   d  and an internal thread  278   e  at its downstream end. The fixing pipe  278   a  is inserted in the wash water discharge hole  211   e  at its downstream end. A seal member  280  is disposed between the flange  278   c  and the side wall of the bowl  211 . A tip pipe  290  is provided with a flange  290   a  and an external thread  290   b . The external thread  290   b  of the tip pipe  290  is screwed into the internal thread  278   e  of the fixing pipe  278   a . The flange  278   c  and the flange  290   a  collaborate to clamp the side wall of the bowl  211  and the seal member  280 . 
   The sectional area of the wash water passage downstream of the exhaust nozzle  273  is set larger than that of the exhaust nozzle  273 . 
   Operation of the flush toilet  200  will be described. 
   When a user manipulates the manipulation device  244  to initiate flushing of the toilet body, the electromagnetic valve  241  in the valve unit  240  opens, and pressurized wash water with constant flow rate flows in the connection hole  271  of the air mix device  270  through the flow regulating valve  242  and the internal connection pipe  243 . 
   As shown in  FIG. 23 , the wash water passes through the elbow  272  to become turbulent, enters from the elbow  272  into the exhaust nozzle  273  to become further turbulent due to abrupt change of sectional area of wash water passage, and discharges into the air contact chamber  274  filled up with air. The turbulent wash water discharging from the exhaust nozzle  273  into the air forms a turbulent flow structured by a main flow and branched flows having components of flow speed different from that of the main flow. The branched flows project from the surface of the main flow just after discharging to be separated from the main flow due to surface tension and friction force applied by the air around the flows, thereby forming water drops and dispersing radially. When the wash water forms water drops and disperses in the air contact chamber  274 , the contact area between wash water and air increases by a large margin, a large quantity of air is mixed in the wash water stably due to friction, the ratio of the mixed air to the wash water increases, and generation of a bubbly stream of wash water described later is promoted. The water drops dispersing radially flows to the downstream to cause an ejector phenomenon, thereby further entraining air in the wash water. The wash water discharges in parallel with the exhaust nozzle  273  or the air contact chamber  274  because the length of the exhaust nozzle  273  is larger than or equal to a predetermined value, and the water drops disperse uniformly in the air contact chamber  274 . When the exhaust nozzle  273  is too short, the wash water discharges from the exhaust nozzle  273 , while maintaining the component of flow speed which the wash water held before it enters in the elbow  272 , the dispersing water drops are biased to the right in  FIG. 23 , and the quantity of entrained air decreases. The flow regulating valve  242  controls the flow rate of the wash water appropriately to control the flow speed of the wash water in the air contact chamber  274  appropriately, thereby controlling the quantity of the air entrained in the wash water appropriately. Thus, generation of a bubbly stream of wash water is promoted. 
   The pressure in the air contact chamber  274  becomes negative because the wash water discharging from the exhaust nozzle  273  entrains the air in the air contact chamber  274  to flow to the downstream. Thus, air is sucked naturally from the air intake  279   a  into the air contact chamber  274  through the air intake pipe  279 . Freedom in arranging the air intake  279   a  increases owing to the provision of the air intake pipe  279 . Therefore, it becomes possible to arrange the air intake  279   a  at a place shielded from the line of sight of a user of the flush toilet and free from splashed water. Provision of the air intake pipe  279  makes it possible to keep noise generated in the air mix chamber  276  apart from the user, thereby enhancing the quietness of the flush toilet  200 . 
   As shown in  FIG. 24 , wash water  301  enters in the air mix chamber  276  at high speed to collide against the bent side wall of the air mix chamber  276 , thereby being broken up. A part of the broken up wash water reflects toward the air contact chamber  274  to be stored temporarily in the air mix chamber  276 , thereby forming stored water  302 . Succeeding wash water  301  rushes into the stored water  302  at high speed. When the succeeding wash water rushes into the stored water, a large quantity of air entrained into the wash water  301  in the air contact chamber  274  forms lumps of air  303 . The lumps of air  303  are mixed in the stored water  302 . Succeeding wash water  301  rushes into the stored water  302  and the lumps of air  303  to break up the lumps of air  303 , thereby forming an abundance of micro air bubbles  304  and dispersing them in the stored water  302 . A part of the wash water  301  broken up by the bent side wall of the air mix chamber  276  reflects toward the rectification chamber  277  to entrain the stored water  302  containing an abundance of dispersed micro air bubbles  304 , thereby forming a bubbly stream of wash water containing an abundance of dispersed micro air bubbles. The bubbly stream of wash water flows into the rectification chamber  277 . 
   When the wash water  301  rushes into the stored water  302 , a part of the stored water  302  forms splashing water  305  directed to the air contact chamber  274 . The splashing water  305  flows back along the side wall of the check chamber  275  and is prevented from further flowing back by the barrier  275   a . Thus, the wash water is prevented from flowing back into the air intake pipe  279 . Therefore, air is sucked into the air contact chamber  274  stably. 
   The bubbly stream of wash water flowing into the rectification chamber  277  swirls because the wash water  301  colliding against the bent side wall of the air mix chamber  276  is applied with a non-uniform force from the side wall. When the bubbly stream of wash water passes through the rectification chamber  277 , the rectification fins  277   a  extinguish the swirling motion of the bubbly stream of wash water. Thus, air-wash water separation is prevented. 
   The bubbly stream of wash water flows into the connection pipe  278  from the rectification chamber  277 . When the bubbly stream passes through the connection pipe with appropriate length, distribution of flow speed of the bubbly stream is made uniform. Neither turbulence nor air-wash water separation is generated in the bubbly stream because the connection pipe  278  is straight. 
   The bubbly stream flows into the fixing pipe  278   a  from the connection pipe  278  to be rectified with the rectification fins  278   b , thereby being prevented from air-wash water separation. The bubbly stream passes through the tip pipe  290  and discharges into the bowl  211 . The apparent volume of the wash water increases due to mixing air into the wash water. Nevertheless, the wash water passes through wash water passages downstream of the exhaust nozzle  273  without difficulty and discharges from the tip pipe  290  because the sectional areas of the wash water passages downstream of the exhaust nozzle  273  are larger than that of the exhaust nozzle  273 . The wash water rectified with the rectification fins  278   b  passes through the tip pipe  290  formed highly accurately to discharge with appropriate thickness, thereby enabling stable flushing of the toilet body. The flange  290   a  prevents sewage, chemicals, etc. from entering into the discharge hole  211   e  from the bowl  211  to prevent deterioration of the seal member  280  and enhance the durability and reliability of the seal member  280 . The tip pipe  290  can be installed easily from side of the bowl  211 . When the flange  290   a  is made thin, it projects little from the dry surface  211   b , soil adheres little to the flange  290   a  to be removed easily from the flange  290   a , and the good appearance of the dry surface  211   b  is enhanced. 
   The bubbly stream of wash water discharges from the tip pipe  290  substantially horizontally along the annulus concave  211   c . The bubbly stream of wash water does not cause heavy splashing or loud noise when it collides against the dry surface  211   b . Thus, sanitary and quiet flushing of the dry surface  211   b  is achieved. The bubbly stream of pressurized wash water has large detergency because it flows at high speed. The bubbly stream of wash water swirls along the dry surface  211   b  to wash it. The overhang  211   d  prevents the wash water from splashing out the toilet body  211 . The bubbly stream of wash water swirling along the dry surface  211   b  dwells for a long time on the dry surface  211   b  to wash the dry surface  211   b  strongly. The bubbly stream of wash water has strong detergency because it generates high-frequency vibration. Therefore, the bubbly stream of wash water washes the dry surface  211   b  strongly. The wash water used for flushing the dry surface  211   b  is saved by mixing an abundance of air bubbles in the wash water. 
   The wash water swirls by 360 degrees of more along the dry surface  211   b  to join the water seal RW. The swirling wash water drives the water seal RW to swirl, makes it flow into the trap-way  214  promptly, generates a siphon phenomenon promptly, and discharges soil from the toilet body promptly. 
   Succeeding wash water flows into the empty bowl  211  to form the water seal RW. Under the control by the manipulating device  244 , the electromagnetic valve  241  closes, discharge of the wash water from the tip pipe  290  stops, and the flushing of the toilet body is completed. 
   The present invention is not limited to the aforementioned embodiments. 
   In any one of the first to the fourth preferred embodiments, a plurality of nozzles  166  may be disposed apart from each other by a predetermined distance and connected to the rim water pipe  160  through branched pipes. Each of the pressurized wash waters discharging from the plurality of nozzles  166  washes the inner surface of the bowl to enhance the detergency of the flush toilet. The plurality of nozzles  166  may be directed in the same swirling direction or different swirling directions. The aforementioned variation can be applied to the fifth preferred embodiment. 
   In the first or second preferred embodiment, it is possible to connect a tank directly to the toilet body, and discharge non-pressurized wash water led from the tank as jet flush water BS or the second rim flush water RBS. The jet flush water BS or the second rim flush water RBS does not contribute to flushing the dry surface  111   b . Therefore, non-pressurized wash water led from a tank directly connected to the toilet body may be used as jet flush water BS or the second rim flush water RBS in a district or in a house where pressurized wash water with ample flow rate cannot be obtained. 
   In the first or the second preferred embodiment, it is possible to discharge the jet flush water BS or the second rim flush water RBS after the discharging of the rim flush water RS is finished. It can be assumed that the rim flush water RS reaches the water seal RW before the discharge of the rim flush water RS finishes. Therefore, when the jet flush water BS or the second rim flush water RBS discharges after the discharge of the rim flush water RS finishes, the rim flush water RS and the jet flush water BS, or the rim flush water RS and the second rim flush water RBS entrain the water seal RW to promote its flow into the trap-way  114 . Thus, the trap-way  114  is filled up with the wash water promptly, a siphon phenomenon appears promptly, the time necessary for flushing the toilet body becomes short, and the quantity of wash water necessary for flushing the toilet body diminishes. 
   In any one of the first to the fourth preferred embodiments, electromagnetic valves controlled by an electronic circuit or any other valve device controlled by a controller may be used instead of the mechanical valve controller  5  and the pilot operated valve device  21 . 
   In the third preferred embodiment, it is possible to dispose a pair of rim water pipes  160  and a pair of nozzles  166  in parallel above and below as shown in  FIG. 25 , and connect the pair of rim water pipes  160  to the valve unit  140 . The pair of nozzles  166  discharge pressurized wash water simultaneously to form wide swirling flow of the rim flush water RS, thereby enhancing the detergency of the rim flush water. 
   In  FIG. 25 , the lower rim water pipe  160  and the lower nozzle  166  may be moved to the right annulus concave  111   c . In this case, it is desirable to dispose the right nozzle  166  at a level higher or lower than that of the left nozzle  166  to prevent the rim flush waters RS discharging from the right and left nozzles  166  simultaneously from colliding against each other. 
   In the fifth preferred embodiment, it is possible to connect the connection hole  271  to the exhaust nozzle  273  with a straight pipe  272   a  instead of the elbow  272 , and dispose a plurality of half-disk shaped baffle plates  272   b  distanced from each other in the straight pipe  272   a , in staggered arrangement and at right angles to the flow of the wash water, as shown in FIG.  26 . The wash water becomes turbulent when it passes by the baffle plates  272   b  and when it enters into the exhaust nozzle  273  to form water drops and disperses radially in the air contact chamber  274 . 
   In the fifth preferred embodiment, it is possible to connect the connection hole  271  to the exhaust nozzle  273  with a straight pipe  272   a  instead of the elbow  272 , and dispose a twisted baffle plate  272   c  in the straight pipe  272   a , as shown in FIG.  27 . The wash water becomes turbulent when it passes by the twisted baffle plate  272   b  and when it enters into the exhaust nozzle  273  to form water drops and disperses radially in the air contact chamber  274 . Flow resistance of the baffle plate  272   c  is smaller than that of the baffle plate  272   b . Thus, energy loss due to generation of turbulence decreases. 
   In the fifth preferred embodiment, it is possible to connect the connection hole  271  to the exhaust nozzle  273  with a straight pipe  272   a  instead of the elbow  272 , and dispose an ultrasonic vibrator  272   d  around the straight pipe  272   a , as shown in FIG.  28 . The wash water passing through the straight pipe  272   a  is vibrated to generate micro air bubbles in it. The bubbles in the wash water are compressed when the wash water passes through the exhaust nozzle  273  with small diameter. The compressed air bubbles grow rapidly just after the wash water discharges from the exhaust nozzle  273  to explode. Thus, the wash water around the air bubbles is broken up to form water drops, thereby dispersing radially in the air contact chamber  274 . 
   In the fifth preferred embodiment, it is possible to engage a grid member  274   b  supporting a column  274   a  with a plurality of projections  274   c  formed on the circumferential wall of the air contact chamber downstream of the air intake pipe  279  and locate the column  274   a  opposite the exhaust nozzle  273 , as shown in FIG.  29 . The wash water discharging from the exhaust nozzle  273  collides against the column  274   a  to be broken up, thereby forming water drops and dispersing radially. When the column  274   a  is located downstream of the air intake pipe  279 , the wash water broken up by the column  274   a  is prevented from entering into the air intake pipe  279 . A rod member with any other shape may be used instead of the column  274   a.    
   In the fifth preferred embodiment, it is possible to dispose a plurality of small discharge holes  273   a  directed radially or aslant relative to the direction to the downstream and connect the connection hole  271  to the exhaust nozzle  273  with a straight pipe  272   a  instead of the elbow  272  as shown in FIG.  30 . When the wash water discharges from a plurality of exhaust nozzle  273   a , the contact surface area between the wash water and the air increases, and the quantity of air entrained by wash water increases. When a plurality of wash water flows discharge radially or aslant, the quantity of air entrained by the wash water increases. The quantity of air entrained by the wash water can be adjusted by adjusting the number the discharge holes  273   a  or the angle of radiation of the discharge holes  273   a.    
   In the fifth preferred embodiment, it is possible to dispose a large exhaust nozzle  273   b  conically increasing in diameter toward the downstream, connect the connection hole  271  to the exhaust nozzle  273  with a straight pipe  272   a  instead of the elbow  272 , dispose a baffle plate  273   c  conically increasing in diameter toward the downstream in the exhaust nozzle  273   b , and support the baffle plate  273   c  with an appropriate support member, as shown in FIG.  31 . The wash water passes through an annulus space between the exhaust nozzle  273   b  and the baffle plate  273   c  increasing in diameter toward the downstream, discharges from the annulus space, and forms a water screen to spread in the air contact chamber  274 . Thus, the contact surface area between the wash water and air increases and the quantity of air entrained by wash water increases. 
   The aforementioned devices for dispersing wash water may be combined. In this case, the contact surface area between the wash water and air in the air contact chamber  274  increases and the quantity of air entrained by wash water increases. 
   In the fifth preferred embodiment, it is possible to dispose a check valve  300  in the air intake  279   a  as shown in FIG.  32 . The check valve  300  is provided with a plurality of support projections  301  fixed on a flange like expansion  279   b  formed at the upstream end of the air intake pipe  279 , a flange like valve seat  302  fixed on the upstream end of the air intake pipe  279 , and a movable valve body  303  disposed between the flange like expansion  301  and the flange like valve seat  302 . The movable valve body  303  is made of a material with density smaller than that of wash water. 
   When the air intake pipe  279  operates normally, the movable valve body  303  leaves the valve seat  302  under its own weight to engage the support projections  301 . When the pressure in the air contact chamber  274  become negative, air is sucked into the air intake pipe  279  through spaces between adjacent support projections  301  to be sucked into the air contact chamber  274  through the air intake pipe  279 . When the air contact chamber  274  is filled up with wash water and the wash water flows back into the air intake pipe  279  due to some cause, the movable valve body  303  is applied with buoyancy from the wash water to leave the support projections  301  and abut against the valve seat  302 . Thus, the check valve  300  closes to prevent the wash water from flowing out the air intake pipe  279 . 
   In the fifth preferred embodiment, it is possible to form a swelling  279   c  in the middle of the air intake pipe  279  as indicated by chain lines in FIG.  33 . The swelling  279   c  operates as a silencer to prevent noise generated when air is mixed in wash water in the air mix chamber  276  from leaking outside. 
   In the fifth preferred embodiment, it is possible to elongate the air intake pipe  279  to connect the air intake  279   a  to a hole formed in the inner surface of the bowl  211  above the water seal RW, desirably above the discharge hole  211   e  as indicated by two-dot chain lines in FIG.  33 . When the air contact chamber  274  is filled up with wash water and the wash water flows back into the air intake pipe  279  due to some cause, the wash water is discharged in the bowl  211 . Therefore, the flush toilet is free from leakage of wash water and sanitary. The air passing trough the air intake pipe  279  at high speed is prevented from contacting the wash water. Thus, quietness of the flush toilet  200  is enhanced. When the elongated part of the air intake pipe  279  extends aslant downward to the bowl  211  as indicated by two-dot chain lines in  FIG. 33 , discharging of the wash water flowing back to the air intake pipe  279  to the bowl  211  is promoted. 
   In any one of the first to the fourth preferred embodiments, the rim water pipe  160  may be reduced in diameter partially, and provided with an air mix device  168  having a cylindrical suction head  168   a  made of porous material such as ceramic, etc., an air chamber  168   b  surrounding the suction head  168   a  and an air intake pipe  168   c  extending from the air chamber  168   b  at its portion with reduced diameter, as shown in FIG.  34 . The wash water flows in the suction head  168   a  at high speed to generate negative pressure in the suction head  168   a . Thus, air is sucked into the air chamber  168   b  through the air intake pipe  168   c , passes through micro pores in the suction head  168   a  to form micro air bubbles, and disperses into the wash water flowing in the suction head  168   a . A bubbly stream of wash water containing an abundance of micro air bubbles dispersed in it discharges from the nozzle  166  to form rim flush water RS composed of a bubbly stream. When the rim flush water RS is composed of a bubbly stream, wash water necessary for flushing the toilet body decreases, while the detergency of the rim flush water RS increases. It is possible to control the flow rate of the wash water with a flow regulating valve, thereby controlling the flow speed of the wash water flowing in the suction head  168   a , optimizing the quantity of the air mixed into the wash water and promoting the generation of the bubbly stream. 
   When the length of the air intake pipe  168   c  is optimized, freedom in arranging the air intake increases. Therefore, it becomes possible to arrange the air intake at a place shielded from the line of sight of a user of the flush toilet and free from splashed water. It becomes possible to keep noise generated in the air mix device apart from the user, thereby enhancing quietness of the flush toilet. 
   It is possible to elongate the air intake pipe  168   c  to connect it to a hole formed in the dry surface  111   b , desirably above the nozzle  166 . When the wash water flows back into the air intake pipe  168   c  due to some cause, the wash water is discharged in the bowl  111 . Therefore, the flush toilet is free from leakage of wash water and sanitary. The air passing trough the air intake pipe  168   c  at high speed is prevented from contacting the wash water. Thus, the quietness of the flush toilet is enhanced. When the elongated part of the air intake pipe  168   c  extends aslant downward to the bowl  111 , discharging of the wash water flowing back to the air intake pipe  168   c  to the bowl  111  is promoted. 
   In any one of the first to the fourth preferred embodiments, the rim water pipe  160  may be provided with an air mix device  169  having a cylindrical suction head  169   a  made of porous material such as ceramic, etc., an air chamber  169   b  surrounding the suction head  169   a  and a compressor  169   c  communicating with the air chamber  168   b , as shown in FIG.  35 . When the compressor  169   c  operates, micro air bubbles are forced to disperse into the wash water flowing in the suction head  169   a . Thus, the ratio of mixed air to the wash water becomes larger than that in the natural suction shown in  FIG. 34 , and the quantity of wash water necessary for flushing the toilet body further decreases. 
   As shown in  FIG. 36 , a bubbly stream of wash water can be used for a flushing type urinal  400 . 
   The flushing type urinal  400  is provided with a bowl  401 , a housing  402  located above the bowl  401  and a valve unit  403  disposed in the housing  402 . The valve unit  403  is connected to a feed water pipe  404  extending from a pressurized water source not shown in Figures. The valve unit  403  is provided with a sensor  403   a  for detecting the human body and a valve linked to the sensor  403 . The valve is not shown in Figures. An air mix device  405  which also serves as a wash water passage extends from the valve unit  403  to connect to a discharge hole  406  formed in the upper end of the side wall of the bowl  401 . As shown in  FIG. 37 , overhangs  401   a  are formed at opposite sides of the bowl  401 . 
   In the flushing type urinal  400 , the valve in the valve unit  403  opens depending on the start signal from the sensor  403   a , wash water flows to the air mix device  405  from the feed water pipe  404  to form bubbly stream, and discharges from the discharge hole  406 . The discharging bubbly stream of wash water spreads radially as indicated by dot lines to flow down along the inner surface of the bowl  401 . The overhangs  401   a  prevent the wash water from splashing out the bowl  401 . The bubbly stream of wash water having strong detergency washes the inner surface of the bowl  401  strongly. 
   INDUSTRIAL APPLICABILITY OF THE INVENTION 
   The flush toilet of the present invention can be used not only for closets but also for urinals.