Patent Publication Number: US-8112829-B2

Title: Flush valve assembly structure of water tank

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to the technical field of water tank parts of a flush toilet, and more particularly to a flush valve assembly structure installed in a water tank and capable of adjusting a flush water volume conveniently. 
     2. Related Art 
     According to flush toilet standards in different countries, it is desired a flush toilet may reduce the flush water volume each time in the flushing operation to save water and protect the environment. Therefore, in current flush toilet designs, mostly the flushing intensity is increased and the flushing time is reduced, so as to ensure that the toilet bowl may be cleansed while satisfying the spirit of environmental protection. Normally, a common design is to install a flush valve assembly on a bottom of a water tank. 
     US Patent No. 20070101485A1 entitled “CANISTER FLUSH VALVE” has disclosed such a structure. The flush valve assembly is normally fixed on a bottom of a water tank by a valve seat. In a normal state, the flush valve assembly blocks and seals a tank outlet on the bottom of the water tank and linking the water tank and a toilet bowl, so as to form a closed space for storing clean flush water in the water tank. When an operator pulls a trip lever, or presses a flush button, a canister flush valve on the flush valve assembly is lifted to be separated from the valve seat, so as to form a valve port through which the flush water flow in the water tank flushes the toilet bowl. In a later period of the flushing process, the flush water in the water tank reduces to a lower level, so the flush valve may be opened, and the valve port is closed. Then, the water is supplemented to prepare for the next flushing. 
     In a current flush valve assembly, a through hole is arranged in a bottom of the canister flush valve. When the valve port is opened and most of the flush water flows to the toilet bowl, a small amount of water flows into the canister flush valve from the through hole, and accumulates in a chamber between an outer cylindrical wall and an inner cylindrical wall. Thus, the accumulated flush water increases the weight of the canister flush valve, so the canister flush valve may drop more rapidly, and the valve port is closed at a higher speed. Thus, the flush water volume used each time is reduced. However, the standards for the flush water volume used each time of the flush toilet are different in different countries, so the design that the flush water flows into the canister flush valve to increase the weight of the canister valve cannot meet the standards specified in all countries. Therefore, it is necessary to develop other designs that may increase the weight of the canister valve, so as to change the speed of closing the valve port and change the flush water volume used each time. 
     In addition, for water tanks of different sizes, as the capacities of the water stored in the water tanks are different, the speeds of closing the valve ports are also different. Therefore, the application lacks flexibility, and the speed for closing the valve port and the flush water volume used each time cannot be adjusted flexibly for different conditions. Thus, it is necessary to further design a flush valve assembly structure that may adjust the flush water volume conveniently. 
     Further, in a current flush valve assembly, the canister flush valve is often sleeved on a guide rod, and a guide edge on the guide rod is used to guide the canister flush valve, such that the canister flush valve may be lifted up and return to the original position smoothly each time. However, in the existing guide rod design, a top end of the guide edge is approximately at the same level as a bottom edge of an annular wall surface in a round rod shape in a top end segment of the guide rod. Therefore, when the canister flush valve is lifted up, the top edge of the inner cylindrical wall may easily be stuck by a bottom plane at the intersection of the annular wall surface in the round rod shape and the top end of the guide edge, which leads to error operation of the canister flush valve, or influences the smoothness of the flushing operation. These problems also need to be solved. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a flush valve assembly structure of a water tank, which generates an umbrella-shaped spray water flow from a part of flush water entering a spraying assembly at a top end of a guide rod in a later period of a flushing process when a water inlet valve is opened. Thus, the umbrella-shaped spray water flow may enter a chamber of the canister flush valve smoothly, so as to increase a weight of the canister flush valve, shorten a valve port closing time, and reduce a flush water volume used each time. Further, a fine noise-prevention effect is achieved in a process for forming a water seal required by a toilet bowl. 
     The present invention is also directed to a flush valve assembly structure of a water tank, which is capable of adjusting a speed of closing a valve port by a canister flush valve conveniently in each flushing operation, so as to adjust and control a flush water volume used in each flushing operation. 
     The present invention is further directed to a flush valve assembly structure of a water tank, in which when a force is applied on the canister flush valve to lift up the canister flush valve, a top edge of an inner cylindrical wall smoothly arrives at a round rod portion of a guide rod instead of being stuck by an intersection of the round rod portion and a guide portion, so as to ensure smoothness of an flushing operation. 
     To achieve the above objectives, the present invention provides a flush valve assembly structure of a water tank, which includes a valve, a guide rod, a canister flush valve, and a water passage part. 
     The valve seat is mounted and fixed on the water tank, and has a longitudinal through hole and a support rib extending into the longitudinal through hole. 
     A bottom end of the guide rod has a fixing portion, which is mounted and fixed on the support rib of the valve seat, and a guide portion is disposed above the fixing portion. 
     The canister flush valve seals the longitudinal through hole of the valve seat in a normal state, and has an annular bottom wall. Inner and outer sides of the bottom wall extend upward to form an inner cylindrical wall and an outer cylindrical wall respectively, so as to define an annular chamber by the inner cylindrical wall, the outer cylindrical wall, and the bottom wall, and flush water is sprayed into the chamber. An inner edge surface of the inner cylindrical wall is guided and positioned by the guide portion of the guide rod, at least one via in a predetermined shape is arranged in the bottom wall, and a periphery of the via extends upward appropriately to form a block wall. The canister flush valve may have an upward displacement along the guide portion of the guide rod, so as to be separated from the valve seat to form a valve port; a spraying assembly, which is mounted and fixed on a top end of the guide rod. A part of supplemented flush water appropriately flows into the spraying assembly, and then forms the umbrella-shaped spray water flow and flows into the chamber of the canister flush valve. 
     A round rod portion is disposed on the top end of the guide rod of the flush valve assembly structure of the water tank, so as to form a round annular wall surface. The round rod portion extends downward to form the guide portion, and a plurality of guide rib plates distributed at equal angles is formed around the guide portion. A guide edge is formed at an edge of each of the guide rid plates. Top ends of the guide edges of the guide rib plates connected to the annular wall surface slightly protrude from the annular wall surface radially, and extend upward with small segments on the annular wall surface. 
     In the flush valve assembly structure of a water tank of the present invention, by using the spraying assembly mounted at the top end of the guide rod, in the later period of the flushing process when the water inlet valve is opened, a part of the flush water flowing into the spraying assembly may form an umbrella-shaped spray water flow, and flow into the chamber, so as to increase the weight of the canister flush valve, and reduce the time when the canister flush valve drops to close the valve port. Further, by adjusting the relative positions of the water inlet of the water passage post of the water passage part and the block wall around the via of the canister flush valve, the volume of the flush water in the water tank flowing into the chamber through the water passage post after the valve port is opened may be adjusted, so as to adjust the closing time of the valve port. Thus, the standards in different countries can be satisfied. In addition, after the valve port is closed, the umbrella-shaped spray water flow may provide the water seal required by the toilet bowl, and as the umbrella-shaped spray water flow flows down along the inner wall surface of the outer cylindrical wall, no noise is generated when the water flows, and a fine noise-prevention effect is achieved in the process of forming the water seal. 
     Moreover, the top ends of the guide edges of the guide rod portion slightly protrude radially and extend to the annular wall surface of the round rod portion longitudinally, so when a force is applied on the canister flush valve to lift up the canister flush valve, top edges of the inner cylindrical wall may arrive at the round rod portion smoothly, and will not be stuck by a bottom surface of the round rod portion at the intersection of the round rod portion and the guide portion, which ensures that each flushing operation is smoothly and stably performed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is a combined outside view of the flush valve assembly of the present invention; 
         FIG. 2  is a three-dimensional exploded view of the flush valve assembly of the present invention; 
         FIG. 3  is a combined cross-sectional view of the flush valve assembly mounted on a bottom wall of the water tank of the present invention; 
         FIG. 4  is a three-dimensional outside view of a guide rod of the present invention; 
         FIG. 5  is a cross-sectional side view of a spraying part and a cover in a combined state of the present invention; 
         FIG. 6  is a partial bottom view of the canister flush valve of the present invention; 
         FIG. 7  is a partial schematic structural view of a water passage part and the canister flush valve in a combined state of the present invention; 
         FIG. 8  is a top view of the water passage part and the canister flush valve in a combined state of the present invention; 
         FIG. 9  is a three-dimensional outside view of the water passage part of the present invention; 
         FIG. 10  is a bottom view of the water passage part of the present invention; 
         FIG. 11  is a schematic view of the motion that the canister flush valve is lifted up and is separated from the top edge of the longitudinal through hole of the valve set to form a valve port of the present invention; 
         FIG. 12  is a schematic view of the canister flush valve of the present invention in a state that the flushing operation is completed and the valve port is closed, and in a state that the umbrella-shaped spray water flow generated by the spraying part flows to the valve seat along the inner cylindrical wall; 
         FIG. 13  is a schematic structural view of the water passage part and the bottom wall of the canister flush valve according to a second embodiment of the present invention; 
         FIG. 14  is a schematic cross-sectional view of the adjustment of the water passage part according to the second embodiment of the present invention; 
         FIG. 15  is a schematic structural view of the water passage part and the bottom wall of the canister flush valve according to a third embodiment of the present invention; and 
         FIG. 16  is a schematic cross-sectional view of the adjustment of the water passage part according to the third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 3  are structural views of a flush valve assembly structure of a water tank according to a preferred embodiment of the present invention.  FIG. 1  is a combined outside view of the flush valve assembly of the present invention,  FIG. 2  is a three-dimensional exploded view of the flush valve assembly of the present invention, and  FIG. 3  is a combined cross-sectional view of the flush valve assembly mounted on a bottom wall of the water tank of the present invention. 
     The flush valve assembly is mounted and fixed on a mounting hole  81  of the bottom wall  80  of a common water tank (as shown in  FIG. 3 ). The flush valve assembly mainly includes a valve seat  10 , a locking member  20 , a guide rod  30 , a spraying assembly  40 , a canister flush valve  50 , a water passage part  60 , and an overflow pipe  70 . 
     The valve seat  10  is approximately tube-shaped, and has a longitudinal through hole  11 . A support rib  12  extends in the longitudinal through hole  11 . In this embodiment, the support rib  12  is formed by four rib plates  121  arranged in a cross shape and a pipe post  122  connecting the rib plates  121  at the center. A cross-shaped positioning perforation  123  is arranged through the pipe post  122 . Meanwhile, the support ribs  12  define a plurality of flow paths  13  in an inner wall of the longitudinal through hole  11 . A pressing plate  14  extends from an outer edge near an upper part of the valve seat  10  radially, and the valve seat  10  has an external screw thread  15  below the pressing plate  14 , for passing through the fixing hole  81  in the bottom wall  80  of the water tank. A water proof washer  16  is sleeved on the outer edge of the valve seat  10  below the pressing plate  14 . 
     The locking member  20  is screwed on the external screw thread  15  of the valve seat  10  passing through the mounting hole  81  of the water tank. The valve seat  10  is locked to the bottom wall  80  of the water tank, and the water proof washer  16  sleeved on the valve seat  10  is fixed and pressed between the bottom wall of the pressing plate  14  and the corresponding bottom wall  80  of the water tank. 
       FIG. 4  is a three-dimensional outside view of a guide rod of the present invention. Referring to  FIG. 4 , the guide rod  30  includes a round rod portion  31 , a guide portion  32 , and a fixing portion  33  sequentially from the top end to the bottom. The round rod portion  31  has a round annular wall surface  311 , a transverse rabbet  312  is disposed through the annular wall surface  311  at an appropriate position, and an insertion hole  313  in communication with the transverse rabbet  312  is disposed on the top end of the round rod portion  31 . The round rod portion  31  extends downward to form the guide portion  32 , and four guide rib plates  321  are disposed at a periphery of the guide portion  32  at equal angles. A guide edge  322  is formed at an edge of each of the guide rid plates  321 . Top ends  323  of the guide edges  322  of the guide rib plates  321  connected to the annular wall surface  311  slightly protrude from the annular wall surface  311 , and extend upward with small segments on the annular wall surface  311 . The guide portion  32  extends downward to form the fixing portion  33 , and an annular block wall  331  extending in a radial direction is formed on the fixing portion  33 . The annular block wall  331  bears against a top surface of the pipe post  122  of the valve seat  10  to limit the position of each other. Further, four clips  332  arranged in a cross shape are disposed below the annular block wall  331 , which may be engaged with the cross-shaped positioning perforation  123  of the pipe post  122  of the valve seat  10  to fix each other, and to limit the rotation of the guide rod  30 , so as to fix the guide rod  30  on the valve seat  10 . 
       FIG. 5  is a cross-sectional side view of a spraying part and a cover in a combined state of the present invention. The spraying assembly  40  includes a spraying part  41 , a cover  42 , and a locking block  43 . The spraying part  41  has a positioning tube post  411 , which has four positioning ribs  412  distributed at equal angles on a peripheral wall, and has a water inlet  413  on a top end. The water inlet  413  provides a pipeline communication of the flush water, so as to receive the flush water appropriately. Four spraying holes  414  are arranged through the peripheral wall of the positioning tube post  411  at equal angles, which may be in communication with the water inlet  413 . A receiving plate  415  extends outward from the peripheral wall of the positioning pipe post  411  below the spraying holes  414  radially, and a stud  416  that may be inserted into the insertion hole  313  at the top end of the guide rod  30  extends from the lower part of the receiving plate  415 . The cover  42  has a positioning bushing  421 , which sleeves on and is positioned by the positioning pipe post  411  of the spraying part  41 , such that an inner wall of the positioning bushing  421  is pressed against the positioning ribs  412  on the peripheral wall of the positioning pipe post  411  for positioning. In addition, a hood-shaped cover plate  422  slightly inclining downward extends outwards from the bottom end of the positioning bushing  421  radially, which covers the receiving plate  415  from the above, such that an annular flow path  417  in communication with the spraying holes  414  and an annular spraying nozzle  418  inclining downward are defined between the cover plate  422  and a top surface of the receiving plate  415 . Thus, the flush water from the water inlet  413  may be sprayed downward in an umbrella shape, as shown in  FIG. 12 . The locking block  43  may be inserted into and fixed in the transverse rabbet  312  near the top end of the guide rod  30 , and may be screwed with the stud  416  inserted to the bottom end of the spraying part  41  through the insertion hole  313  at the top end of the guide rod  30 . 
       FIG. 6  is a partial bottom view of the canister flush valve of the present invention,  FIG. 7  is a partial schematic structural view of a water passage part and the canister flush valve in a combined state of the present invention, and  FIG. 8  is a schematic expanded planar view of the water passage part and the canister flush valve structure of the present invention. 
     The canister flush valve  50  is cylinder-shaped, and has an annular bottom wall  51 . An inner cylindrical wall  52  and an outer cylindrical wall  53  extend from inner and outer sides of the bottom wall  51  respectively, so as to define an annular chamber  54  in the inner cylindrical wall  52 , the outer cylindrical wall  53 , and the bottom wall  51 . A part of the flush water flows into the chamber  54 . 
     An annular attaching surface  511  depresses from the bottom surface of the bottom wall  51 , as shown in  FIG. 6 . The attaching surface  511  has four arc-shaped vias  512  extending along a circumferential direction. Further, two positioning grooves  514  in an arc hole shape and extending along the circumferential direction are symmetrically disposed through the attaching surface  511  at appropriate positions. A plurality of positioning tooth grooves  516  are formed at two symmetric parts on a step wall  515  around the attaching surface  511 . 
     The inner cylindrical wall  52  sleeves on the guide rod  30 , and the inner edge of the inner cylindrical wall  52  is appropriately guided and positioned by the guide edges  332  on the guide rod  30 . A baffle  521  radially protrudes from the inner cylindrical wall  52  at a position at a predetermined distance to the bottom wall  51 . A block wall  522  corresponding to each of the vias  512  is formed on the baffle  521 . Each block wall  522  extends downward from one end to the other end of the via  512  in an inclined manner. A plurality of water outlets  523  through the chamber  54  is disposed at a junction of the inner cylindrical wall  52  and the bottom wall  51 . 
     A water proof washer  55  is embedded on the canister flush valve  50  approximately at the bottom end of the outer cylindrical wall  5 . In a normal state, the water proof washer  55  urges against and seals the top edge of the longitudinal through hole  11  of the valve seat  10 . A bump  531  extends from a peripheral wall of the outer cylindrical wall  53 . A pulling hole  532  is arranged in the bump  531 , which may be connected to a chain or a lever (not shown), so as to be driven by the operation. Thus, the canister flush valve  50  may be properly pulled up, such that the water proof washer  55  is separated from the top edge of the valve seat  10  to form a valve port  56 , as shown in  FIG. 11 . 
       FIG. 9  is a three-dimensional outside view of a water passage part of the present invention, and  FIG. 10  is a bottom view of the water passage part of the present invention. Referring to  FIGS. 9 and 10 , the water passage part  60  has a sheet-shaped annular portion  61 , which is attached on the attaching surface  511  on the bottom of the canister flush valve  50 , and is engaged with the step wall  515  around. A bump  611  corresponding to each of the positioning tooth grooves  516  is disposed on the periphery of the annular portion  61 , and a groove  610  corresponding to each of the bumps  611  is opened in the annular portion  61 . The grooves  610  extend inward from the outer edge of the annular portion  61 , and further extend a distance in a direction approximately parallel to the outer edge of the annular portion  61 , such that the annular portion  61  has a space that allows a part of the bumps  611  to have an inward elastic deformation. Thus, the bumps  611  may be engaged with and positioned by the positioning tooth grooves  516 . Meanwhile, a detent bump  612  is disposed at two symmetric positions on the bottom surface of the annular portion  61  respectively, as shown in  FIG. 10 , such that the operator may apply a pulling force to adjust the position of the water passage part  60 . 
     A through hole  613  is disposed at positions corresponding to the vias  512  on the annular portion  61  respectively, and a water passage post  62  integrally extends upward from the top end of each of the through holes  613  on the annular portion  61 . Thus, the water passage posts  62  may extend upward through the vias  512  of the bottom wall  51 , as shown in  FIGS. 7 and 8 , and have an arc displacement in the vias  512  along with the rotation adjustment of the water passage part  60 . A water inlet  622  in communication with the through holes  613  on the bottom is formed on each of the water passage posts  62 , and an arc protrusion  623  is formed on the inner edge of each of the water passage posts  62  at a position corresponding to the water inlets  622 , such that the water inlet  622  is in a shape that gradually expands upward. Moreover, the displacement of the water passage posts  62  may change the distance to the block walls  522  (as shown in  FIG. 8 ). Insertion posts  63  extend from the top surface of the annular portion  61  at positions corresponding to the positioning grooves  514  respectively. The top ends of the insertion posts  63  are approximately reverse hook-shaped, and a slot  631  is cut in the top end of each of the insertion posts  63 . Thus, the top ends may be elastically compressed to pass through the positioning grooves  514  of the bottom wall  51 , and then recover and expand to be engaged with and positioned by the top surface of the bottom wall  51 , so as to mount and fix the water passage part  60  on the bottom wall  51  of the canister flush valve  50 . Meanwhile, the insertion posts  63  may also be adjusted along with the rotation of the water passage part  60 , so as to have an arc displacement in the positioning grooves  514 . In the water passage part  60  according to this embodiment of the present invention, the bumps  611  around are engaged with the corresponding positioning tooth grooves  516  disposed on the bottom of the canister flush valve  50 , so as to provide multi-step adjustment and positioning. In other words, when the bumps  611  and the positioning tooth grooves  516  are not used, the stepless adjustment may be achieved, which also meets the technical spirit of the present invention. 
     Finally, referring to  FIG. 2 , a connection base  71  is disposed at the bottom of the overflow pipe  70 . The connection base  71  is hollow, and is in communication with the overflow pipe  70 . Further, a socket  17  corresponding to the connection base  71  is disposed on the valve seat  10 . The socket  17  passes through the valve seat in an approximately parallel direction, such that the overflow pipe  70  and the connection seat  71  are in communication with the flow path  13 . 
     The flush valve assembly of a water tank of the present invention is mounted at the mounting hole  81  in the bottom wall  80  of a common water tank. When the operator pulls a trip lever or presses a flush button, the canister flush valve  50  may be pulled up through the chain or lever, such that the water proof washer  55  on the bottom of the canister flush valve  50  is separated from the top edge of the longitudinal through hole  11  of the valve seat  10 , so as to form a valve port  56 , as shown in  FIG. 11 . Thus, the clean flush water accumulated in the water tank flows through the valve port  56  and the flow path  13  formed in the longitudinal through hole  11  of the valve seat  10  into the toilet bowl for flushing the toilet. In the early period after the canister flush valve  50  is lifted up, the bottom is much lower than the flush water in the water tank. Therefore, most of the flush water will flow to the valve seat  10  through the valve port  56 , while a small part of the flush water will flow into and be accumulated in the chamber  54  through the through holes  613  in the water passage part  60  on the bottom of the canister flush valve  50  and the water inlets  622  of the water passage posts  62 . After the canister flush valve  50  is released, the weight of the accumulated flush water in the chamber  54  increases the speed that the canister flush valve  50  drops, such that the canister flush valve  50  closes the valve port  56  in a shorter time, as shown in  FIG. 12 , which enables the flush water volume to meet the standards of different countries. 
       FIG. 12  is a schematic view of the canister flush valve of the present invention in a state that the flushing operation is completed and the valve port is closed, and in a state that the umbrella-shaped spray water flow generated by the spraying part flows to the valve seat along the inner cylindrical wall. According to the design of the spraying assembly  40  of the present invention, when the flush water in the water tank reduces to a low level, and the water inlet valve is opened, the generated umbrella-shaped spray water flow is used to provide the flush water to the chamber  54  of the canister flush valve  50 , so as to increase the weight of the flush water accumulated in the chamber  54 , and increase the speed that the canister flush valve  50  drops. Thus, the canister flush valve  50  may close the valve port  56  in a shorter time. The spraying assembly  40  of the present invention may greatly shorten the closing time of the valve port  56 . 
     The water passage part  60  of the present invention is arranged to adjust the closing time of the valve port  56 . As the standards in different countries are also different, by rotating the water passage part  60  to adjust its position, the distance between the water inlets  622  of the water passage posts  62  and the block walls  522  may be changed, so as to control the total volume of the water flow in a unit time. When the distance between the water inlets  622  and the block walls  522  is greater, the weight of the flush water accumulated in the chamber  54  in a short time will be greater, such that the canister flush valve  50  drops at a higher speed, and the valve port  56  is closed in a shorter time. On the contrary, when the distance between the water inlets  622  and the block walls  522  is smaller, the valve port  56  will be closed in a longer time. Certainly, the change of the distance between the water inlets  622  of the water passage posts  62  and the block walls  522  also influence the buoyancy on the canister flush valve  50  to some extent. When the distance between water inlets  622  and the block walls  522  is smaller, the buoyancy is greater; when the distance between the water inlets  622  and the block walls  522  is greater, the buoyancy is smaller, that is, the canister flush valve  50  will drop at a higher speed. 
     In addition, after the water passage part  60  is mounted, the adjustment to the closing speed of the valve port  56  may be performed conveniently in actual operations. By lifting up the canister flush valve  50  to a height that allows the user to extend hands into the bottom, and appropriately pulling and turning the two detent bumps  612  on the bottom of the water passage part  60 , the water passage posts  622  of the water passage part  60  may have arc displacement in the vias  512  of the canister flush valve  50 , so as to change the distance between the water inlets  622  and the block walls  522 . After the adjustment and positioning, the canister flush valve  50  is released to perform the actual operations until the standards are satisfied. Thus, the adjustment operation is completed conveniently. 
     Moreover, when the water passage part  60  uses the multi-step adjustment structure according to the preferred embodiment, in the adjustment operation, the desired position may be achieved through the engagement between the bumps  611  of the water passage part  60  and the positioning tooth grooves  516  of the canister flush valve  50 . 
     In the later period of the flushing process of the present invention, as the flush water in the water tank reduces to a lower level, the water tank will open the water inlet valve to supplement the water, and the canister flush valve  50  will close the valve port  56 . The supplemented flush water supplements the water in the water tank, and a part of the flush water will flow into the chamber  54  through the umbrella-shaped spray water flow from the water inlet  413  of the water spraying part  41 . Finally, the flush water flows to the toilet bowl from the water outlets  523  of the canister flush valve  50  through the flow path  13  of the valve seat  10 , as shown in  FIG. 12 . When the flush water in the water tank reaches a high level, and the water inlet valve is closed, the water seal required by the toilet bowl may be formed. 
     The height of the overflow pipe  70  may be varied (cut) according to the capacity and form of the water tank, so as to limit the water level in the water tank, such that the water accumulated in the water tank does not overflow the water tank. That is, when the water level control mechanism of the water tank fails, if the level of the accumulated water in the water tank exceeds the top of the overflow pipe  70 , the water will flow into the overflow pipe  70 , and then flow into the toilet bowl through the connection seat  71  and the flow path  13 . 
     In addition, the canister flush valve  50  also has the overflow function. When the top edge of the canister flush valve  50  is consistent with the upper limit of the water level in the water tank, the components such as the overflow pipe  70  may be omitted. When the water level is higher than the top edge of the canister flush valve  50 , the water will flow into the chamber  54  of the canister flush valve  50 , and then flow to the toilet bowl from the water outlets  523  through the flow path  13 . At this time, the overflow pipe  70  and the connection seat  71  may be omitted, and it is only necessary to use an appropriate water plug (not shown) to seal the socket  17  of the valve seat  10 . 
     According to the above description, the flush valve assembly structure of a water tank of the present invention has the following features and efficacies. 
     1. In the present invention, through the spraying assembly  40  mounted on the top end of the guide rod  30 , a part of the flush water will flow into the water inlet  413  of the spraying part  41  to generate the umbrella-shaped spray water flow in the later period of the flushing process. The part of the flush water flows into the chamber  54  to further increase the weight of the accumulated flush water and reduce the time that the canister flush valve  50  drops to close the valve port  56 . In addition, the umbrella-shaped spray water flow flows along the inner surface of the outer cylindrical wall  53 , so as to prevent the water flow noise, especially when forming the water seal in the toilet bowl, thus achieving a fine noise-prevention effect. 
     2. In the present invention, the water passage part  60  is mounted on the bottom of the canister flush valve  50 , which may be properly adjusted to change the water flow volume between the chamber  54  in the canister flush valve  50  and the flow path  13  of the valve seat  10 . Thus, the weight of the flush water accumulated in the chamber  54  of the canister flush valve  50  in a certain time in the early period of forming the valve port  56  may be changed, so as to adjust the speed that the canister flush valve  50  drops, that is, the closing time of the valve  56  properly. Thus, the standards of different countries are satisfied. 
     3. In the present invention, on the guide portion  32  of the guide rod  30 , the top ends  323  of the guide edges  322  slightly protrude from the annular wall surface  311  of the round rod portion  31  radially, and extend upward longitudinally for a small segment. Thus, when the canister flush valve  50  is lifted up, the top edge of the inner cylindrical wall will be guided to the round rod portion  31  smoothly, and will not be stuck by the bottom plane of the round rod portion  31  at the intersection of the round rod portion  31  and the guide portion  32 , so as to ensure that each flushing operation is performed smoothly. 
     In addition to the water passage post of the water passage part according to the above embodiment, and the matching between the vias of the canister flush valve and the block walls, the present invention may be implemented in other forms, which are not limited to the above description. In principle, the techniques capable of appropriately adjusting the flow volume through the water inlet shall fall into the scope of the present invention. 
       FIGS. 13 and 14  are schematic structural views of a second embodiment of the present invention.  FIG. 13  is a schematic structural view of the water passage part and the bottom wall of the canister flush valve according to the second embodiment of the present invention, and  FIG. 14  is a schematic cross-sectional view of the adjustment of the water passage part according to the second embodiment of the present invention. In this embodiment, the through holes  613   a  of the water passage part  60   a  directly pass through the water passage part  60   a , and a water passage post  57   a  is disposed on the bottom wall  51   a  at positions corresponding to each of the through holes  613   a  respectively. The structure of the water passage post  57   a  is similar to that of the water passage post according to the first embodiment, and also has a water inlet  571   a  at the top edge thereof. 
     When the water passage part  60   a  is turned to have a displacement, the positions of the through holes  613   a  will be staggered with respect to the water inlet  571   a , as shown in  FIG. 14 . Thus, the flow volume of the water inlet may also be adjusted, so as to achieve the same adjustment efficacy as the first embodiment. 
       FIGS. 15 and 16  are schematic structural view of a third embodiment of the present invention.  FIG. 15  is a schematic structural view of the water passage part and the bottom wall of the canister flush valve according to the third embodiment of the present invention, and  FIG. 16  is a schematic cross-sectional view of the adjustment of the water passage part according to the third embodiment of the present invention. In this embodiment, the water passage part  60   b  also has a water passage post  62   b , and a surrounding side wall  58   b  corresponding to the water passage post  62   b  extends upward from one end of the via  512   b  of the bottom wall  51   b , a block wall  59   b  is formed on the top surface of the side wall  58   b , and the side wall  58   b  does not extend to the other end of the via  512   b . An opening  581   b  is disposed on the side wall  58   b  at an appropriate position. 
     When the water passage part  60   b  is turned to have a displacement, the position relationship between the water passage post  62   b  and the block wall  59   b  is changed, such that a part of the water inlet  622   b  is blocked by the block wall  59   b , or the water inlet  622   b  is almost completely blocked by the block wall  59   b , as shown in  FIG. 14 , or the water inlet  622   b  is completely not blocked by the block wall  59   b . Thus, the flow volume of the water inlet may also be adjusted, so as to achieve the same adjustment efficacy as the first embodiment.