Siphon type water closet

Abstract

To provide a siphon-type water closet capable of reliably generating siphonage in a drainage line of a drain socket and preventing clogging of dirt.SOLUTION: The siphon type water closet 1 of the present invention comprises: a toilet bowl body 2 having a drain trap pipeline 12 with an inlet part 12a connected below a bowl part 8; and an external drain pipe 18 provided outside the toilet bowl body, connecting an outlet part of the drain trap pipeline to an inlet part D0 of a floor-side drain pipe D, wherein the drain trap pipeline includes a riser tube 12c and a descent tube 12d, a center O1 of an outlet part of a vertical descent region of the descent tube and a center O2 of the inlet part of the floor-side drain pipe are arranged eccentrically, the external drain pipe 18 includes a connection area S3 and a horizontal area S4, and the horizontal area includes a diameter reduction part 26 that is the most reduced part in the entire external drain pipe.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to flush toilets, and more particularly to siphon-type flush toilets that discharge waste by siphon action. [Background technology]

[0002] Conventionally, as a siphon-type flush toilet that discharges waste by siphon action, for example, as described in Patent Document 1, a floor-standing flush toilet equipped with a drain socket that connects the outlet of the drain trap pipe in the toilet body to a drain port on the floor has been known. This drain socket forms a drain pipe provided outside the toilet body, and its upstream end is connected to the outlet of the drain trap pipe in the toilet body, and it is directed rearward and downward from this upstream end. Furthermore, the drain pipe bends at its lower end downstream (toward the front of the toilet), and then extends forward a predetermined distance by a horizontal pipe to connect to a drain outlet on the floor. Furthermore, a throttle section is provided at the downstream end of the drain pipe of the drain socket connected to this drain outlet to reduce the cross section of the flow path. This throttle section makes it easier for wastewater to fill the drain pipe in the vicinity, ensuring the siphon action. This allows wastewater containing sewage in the drainage pipe of the drain socket to be drained from the drain outlet on the floor surface to the floor-side drain pipe connected downstream of it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-67281 Summary of the Invention [Problem to be solved by the invention]

[0004] With the recent trend toward water-saving siphon flush toilets, an important issue has become how to increase the efficiency of the siphon action in the drain trap pipe and the drain socket downstream of it, while minimizing the amount of water wasted up until the siphon action occurs and ensuring that it occurs early. However, with conventional siphon-type flush toilets, after the air in the floor-side drain pipe passes through the drain outlet and flows into the drain pipe of the drain socket, the air flow that flows back upstream interferes with the siphon action in the drain socket, causing it to become clogged with waste. In addition, if the cross-section of the flow path of the drain socket's drain pipe (for example, part of the horizontal pipe) is reduced in order to improve the starting ability of the siphon action, there is a risk of clogging with filth.

[0005] Therefore, the present invention was made to solve the problems and issues of the prior art mentioned above, and aims to provide a siphon-type flush toilet that can reliably generate a siphon action within the drainage pipe of the drain socket and prevent clogging with waste. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides a siphon-type flush toilet that discharges waste by siphon action, comprising a toilet body equipped with a bowl portion that receives waste, and a drain trap pipe whose inlet portion is connected below the bowl portion, and an external drain pipe that is provided outside the toilet body and connects the outlet portion of the drain trap pipe and the inlet portion of a floor-side drain pipe, the drain trap pipe having an ascending pipe that rises from the downstream side of the inlet portion to a top portion rearward and above, and a descending pipe that descends rearward and downward from the top of the ascending pipe, The descending pipeline has a vertically descending region that descends vertically from the upstream side toward the downstream outlet, and the center of the outlet of this vertically descending region and the center of the inlet of the floor-side drain pipe are arranged eccentrically to each other, and the external drain pipeline has a connection region that is connected to the outlet of the vertically descending region, and a horizontal region that extends approximately horizontally from the outlet of this connection region and then connects to the inlet of the floor-side drain pipe, and the horizontal region is characterized by having a reduced diameter section in which the size of the flow path cross section is the smallest in the entire external drain pipeline. In the present invention configured in this manner, the horizontal region of the external drainage pipeline has a reduced diameter section in which the size of the flow path cross section is the smallest in the entire external drainage pipeline, and this reduced diameter section can reduce the space for air to accumulate, so that, for example, air that flows into the horizontal region from the floor side drainage pipe side can be prevented from passing through the reduced diameter section of the horizontal region and flowing into the connection region. In addition, waste matter in the drainage water flowing down from the vertically descending region of the descending pipe of the drain trap pipe in the toilet body into the connection region of the external drain pipe falls with great force from the top of the ascending pipe in the drain trap pipe of the toilet body through the vertically descending region of the descending pipe into the connection region with high potential energy, and due to the momentum of the waste matter, even if the cross-sectional area of the flow path is reduced by the narrowed diameter section in the horizontal region, the waste matter can maintain its momentum along with the flow of the drainage water and pass through reliably without clogging in the horizontal region. As a result, the siphon action can be reliably generated in the external drainage pipe, and clogging with waste can be prevented.

[0007] In the present invention, the reduced diameter portion is preferably formed by reducing the diameter of the top surface side of the flow path cross section of the horizontal region. In the present invention configured in this manner, by reducing the diameter of the top side of the flow path cross section in the reduced diameter section of the horizontal region of the external drainage pipeline, it is possible to reduce the space in which air can accumulate in the upper flow path within the horizontal region. Therefore, it is possible to prevent the siphon action from being impaired by air passing through the external drainage pipe or air accumulation within the flow path.

[0008] In the present invention, the reduced diameter portion is preferably formed so that its flow path cross section is elliptical when viewed from the flow path direction of the horizontal region. In the present invention configured in this manner, even if waste falls with great force from the top of the ascending pipe in the drain trap pipe of the toilet body, through the vertical descending region of the descending pipe, and into the connection region with high potential energy, collides with a part of the connection region, becomes flattened, and is then discharged into the horizontal region, the cross-sectional shape of the flow path in the narrowed diameter portion of the horizontal region is formed in an elliptical shape when viewed from the flow direction of the horizontal region, so the flattened waste can pass smoothly through the elliptical narrowed diameter portion of the horizontal region. Therefore, the waste discharge performance in the horizontal area can be improved.

[0009] In the present invention, preferably, the connection region has a first top surface formed in a straight line in a side view and a bottom surface formed in an approximately arc shape, the horizontal region has a second top surface connected to the first top surface, and the intersection of the first top surface and the second top surface in a side view is located downstream of the center point of curvature of the bottom surface. In the present invention configured in this manner, the intersection between the first top surface of the connection area and the second top surface of the horizontal area in a side view is located downstream of the center point of curvature of the bottom surface of the connection area, so that the top surface side of the flow path cross section of the horizontal area of the external drainage pipeline can be reduced in diameter.

[0010] In the present invention, the first top surface and the second top surface are preferably connected to each other in a polygonal line at the intersection point in a side view. In the present invention configured in this manner, the first top surface of the connection area and the second top surface of the horizontal area are connected to each other in a broken line at the intersection of the two when viewed from the side, thereby reducing the space required for air in the external drainage pipeline to pass in both directions near both top surfaces from upstream to downstream or from downstream to upstream. Therefore, it is possible to prevent the siphon action from being impaired due to air accumulation in the external drainage pipe.

[0011] In the present invention, preferably, the horizontal region is formed so that its flow path cross-sectional shape is maintained substantially uniform from the upstream side to the downstream side, while a portion of the horizontal region forms a curved region that curves upward. In the present invention configured in this manner, the cross-sectional shape of the flow path in the horizontal region is formed while being kept almost uniform from the upstream side to the downstream side, thereby preventing air accumulation and clogging with dirt within the horizontal region. In addition, by forming a curved area in which a portion of the horizontal area bends upward, a water pooling area can be secured upstream of this curved area, thereby improving the starting ability of the siphon action.

[0012] In the present invention, preferably, the connection region has a wall surface facing the first top surface in a side view that has a step portion provided at a height position approximately the same as that of the second top surface of the horizontal region, and the upper surface of this step portion is positioned below the flow path cross section of the vertical descending region. In the present invention configured in this manner, the wall surface opposite the first top surface in a side view of the connection area has a step portion located at a height position approximately equal to the second top surface of the horizontal area, and the upper surface of this step portion is positioned below the flow path cross section of the vertical descending area.Therefore, wastewater that flows down from the vertical descending area of the descending pipe of the drain trap pipe of the toilet body into the connection area of the external drain pipe line collides with the upper surface of the step portion from above, and can then be made watertight up to a height approximately equal to the second top surface in the horizontal area. Therefore, it is possible to eliminate the space for air to accumulate in the horizontal area, and it is possible to prevent the siphon action from being impaired by air accumulation. [Effects of the Invention]

[0013] According to the siphon flush toilet of the present invention, siphon action can be reliably generated within the drain pipe of the drain socket, and clogging with waste can be prevented. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic cross-sectional side view of a siphon flush toilet according to one embodiment of the present invention. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view showing an external drainage pipe of the siphon flush toilet according to one embodiment of the present invention shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0015] A flush toilet according to one embodiment of the present invention will now be described with reference to the accompanying drawings. First, FIG. 1 is a schematic cross-sectional side view of a siphon flush toilet according to this embodiment. As shown in Figure 1, the siphon flush toilet 1 of this embodiment comprises a ceramic toilet body 2 that is placed on the floor F, a flush water supply device 4 provided behind it, and a drain socket 6 that connects the toilet body 2 to a floor-side drain pipe D that extends from below the floor F to above it. As a result, the flush toilet 1 of this embodiment is installed so that the bottom surface of the toilet body 2 is in contact with the floor surface F, making it a so-called "floor-mounted flush toilet," and the toilet body 2 is connected to a floor-side drain pipe D (floor-side drain pipe D) via a drain socket 6, so that wastewater discharged from the toilet body 2 is drained into the floor-side drain pipe D via the drain socket 6, making it a so-called "floor-side drainage system."

[0016] Next, as shown in Figure 1, the toilet body 2 comprises a bowl portion 8 for receiving waste, a rim portion 10 formed on the upper edge of the bowl portion 8, and a drain trap pipe 12 extending from an inlet portion 12a connected to the bottom of the bowl portion 8 to discharge waste within the bowl portion 8. As shown in FIG. 1, the drain trap pipe 12 has an ascending pipe 12c that rises from the downstream side of the inlet 12a to a rearward and upward top 12b, and a descending pipe 12d that descends rearward and downward from the top 12b of the ascending pipe 12c. Furthermore, as shown in FIG. 1, the toilet body 2 is provided with a rim spout 14 provided in the rim portion 10, and a jet spout 16 provided below and outside the bowl portion 8. Here, the rim spout 14 is directed toward the front inside the bowl portion 8, while the jet spout 16 is directed toward the inlet portion 12a of the drain trap pipe 12 at the rear thereof. As a result, the flushing water supplied from the flushing water supply device 4 to the toilet body 2 is discharged W1 (rim discharge W1) from the rim discharge port 114 into the bowl section 8, while the jet discharge port 16 is discharged W2 (jet discharge W2) to spray flushing water toward the inlet section 12a of the forward drain trap pipe line 12. As a result, the flush toilet 1 according to this embodiment is a so-called "siphon-type flush toilet" that uses the siphon action to suck up waste inside the bowl section 8 and discharge it to the outside through the drain trap pipe 12 all at once. The flush toilet 1 of this embodiment employs a toilet flushing method known as "rim-jet flushing," in which the toilet is flushed with flush water (rim water W1, jet water W2) discharged from each of the rim spout 14 and jet spout 16, but this is not limited to this; it is also possible to omit the jet spout 16 and flush the toilet only with flush water (rim water W1) discharged into the bowl section 8 from only the rim spout 14, in other words, a toilet flushing method using "100% rim water discharge."

[0017] As shown in FIG. 1, the flush water supply device 4 employs a tank device that includes a water storage tank (not shown) that stores flush water supplied from a water supply source (not shown) such as a tap, and a pump (not shown) that pressure-feeds the flush water in the water storage tank (not shown) to the toilet body 2, but as the details of these are the same as those of conventional tank devices, explanations thereof will be omitted. The tank device may take the form of a so-called gravity-fed water storage tank, in which flush water stored in a water storage tank (not shown) is supplied to the toilet body 2 using gravity. Alternatively, a flush water supply device 4 other than a tank device may be a direct water pressure type or flush valve type that directly uses the water supply pressure of tap water to supply it directly to the toilet body 2.

[0018] Furthermore, the siphon-type flush toilet 1 of this embodiment may be a so-called tank-type flush toilet, in which flush water stored in a water storage tank (not shown) of the flush water supply device 4 is supplied to each of the rim spout 14 and jet spout 16 of the toilet body 2. Alternatively, the siphon flush toilet 1 of this embodiment may be a so-called hybrid flush toilet in which flush water supplied to the flush water supply device 4 under direct pressure from the water mains is supplied directly to the rim spout 14 of the toilet body 2, and flush water that is supplied and stored in a water storage tank (not shown) of the flush water supply device 4 is supplied to the jet spout 16 of the toilet body by a pump (not shown).

[0019] Next, FIG. 2 is a partially enlarged cross-sectional view showing an enlarged portion of the external drainage pipe 18 of the siphon flush toilet 1 according to the present embodiment shown in FIG. As shown in Figures 1 and 2, the drain socket 6 is provided outside the toilet body 2 and forms an external drain pipe line 18 that connects the outlet portion 12e of the drain trap pipe line 12 and the inlet portion D0 of the floor-side drain pipe D. Here, the descending pipe 12d of the drain trap pipe 12 of the toilet body 2 is provided with a vertically descending region S1 that descends vertically from its upstream side toward the outlet 12e on the downstream side. Furthermore, the central axis A1 (central axis A1 extending in the vertical direction) passing through the center O1 of the flow path cross section of the outlet portion 12e of the vertical descending region S1 is located a predetermined distance behind the central axis A2 (central axis A2 extending in the vertical direction) passing through the center O2 of the inlet portion D0 of the floor-side drain pipe D, and the two centers O1, O2 are arranged eccentrically to each other. Furthermore, as shown in Figure 2, the external drainage pipeline 18 of the drain socket 6 has an upstream region S2, a connection region S3, and a horizontal region S4, respectively, from the upstream end 18a connected to the outlet portion 12e of the vertical descending region S1 of the drain trap pipeline 12 toward the downstream end 18b connected to the inlet portion D0 of the floor-side drain pipe D.

[0020] 2, the upstream region S2 of the external drainage pipe 18 is provided on the upper end side of the drain socket 6, and includes an inlet portion 18a connected to the outlet portion 12e of the vertically descending region S1 of the drain trap pipe 12. An annular elastic seal connection member 20 made of a rubber material or the like is provided on the outer periphery of this inlet portion 18a. By inserting the outlet portion 12e of the drain trap pipe line 12 into this elastic seal connection member 20, the outlet portion 12e of the drain trap pipe line 12 of the toilet body 2 is watertightly connected to the inlet portion 18a of the drain socket 6.

[0021] Also, as shown in Figure 2, the connection region S3 of the external drainage pipeline 18 is a region that connects the upstream region S2 and the horizontal region S4, and its upstream end (upper end) is connected to the vertically descending region S1 of the drainage trap pipeline 12 via the upstream region S2, and the downstream end (front end) of the connection region S3 is connected to the rear end (upstream end) of the horizontal region S4. As shown in Figure 2, the connection region S3 extends generally forward and diagonally downward from its upper end (upstream end), and then its front end (downstream end) is directed toward and connected to the rear end (upstream end) of the horizontal region S4. Furthermore, as shown in Figure 2, the connection region S3 has, in a side view, a top surface 22 (first top surface 22) formed in a linear shape, and a bottom surface 24 formed in an approximately arc shape facing the top surface 22 in the flow path cross-sectional direction.

[0022] Next, the horizontal region S4 of the external drain pipe 18 is a region that extends substantially horizontally forward from the outlet 18c of the connection region S3 and then connects to the inlet D0 of the floor-side drain pipe D. More specifically, this horizontal region S4 has a reduced diameter section 26 extending forward a predetermined distance d1 from its front end (upstream end), an ascending section 28 rising from the downstream side of this reduced diameter section 26 to a top 18d forward and diagonally upward, and a descending section 30 descending from the top 18d to an outlet section 18b forward and diagonally downward (inlet section D0 of the floor-side drain pipe D).

[0023] As shown in FIG. 2, the reduced diameter portion 26 of the horizontal region S4 has a second top surface 26a that is connected to the first top surface 22 of the connection region S3. 2, in the connection region S3, the wall surface 32 on the side facing the first top surface 22 in the front-to-rear direction in a side view has a step portion 34. An upper surface 34a of this step portion 34 is provided at a height position substantially the same as a height position P1 of the second top surface 26a of the horizontal region S4, or at a height position P2 slightly below this height position P1. Furthermore, the upper surface 34a of the step portion 34 is disposed below the flow path cross section C0 of the vertically descending region S1.

[0024] Next, in a side view of the connection region S3 and horizontal region S4 shown in Figure 2, the intersection point Q between the first top surface 22 and the second top surface 26a is located downstream (forward) of the center point O3 of the curvature (curvature radius r1) of the bottom surface 24 of the connection region S3. 2, the first top surface 22 of the connection region S3 forms an inclined surface from the upper rear side toward the lower front side at the intersection point Q in a side view. On the other hand, the second top surface 26a of the horizontal region S4 forms a flat surface from the intersection point Q toward the horizontal front side in a side view. As a result, the inclined surface of the first top surface 22 and the flat surface of the second top surface 26a are connected to each other in a broken line before and after the intersection point Q in a side view.

[0025] Next, FIG. 3 is a cross-sectional view taken along line III-III in FIG. As shown in FIG. 3, the reduced diameter portion 26 of the horizontal region S4 has a flow path cross section C1 that is elliptical when viewed from the flow path direction. Furthermore, as shown in Figures 2 and 3, the elliptical flow path cross section C1 of the reduced diameter section 26 is formed by reducing the diameter on the top surface 26a side of the reduced diameter section 26 compared to the arc-shaped flow path cross section C2 having the same radius as its major axis, and is the part with the smallest flow path cross section in the entire external drainage pipeline 18, and the smallest flow path cross-sectional area. Furthermore, as shown in FIG. 2, the horizontal region S4 is formed so that the cross-sectional shape of the flow path is kept substantially uniform from the upstream side to the downstream side. In particular, a portion of the horizontal region S4 (the ascending section 28 and the descending section 30) bends upward from the downstream side of the reduced diameter section 26 toward the apex 18d, and then forms a bending region S5 that bends forward and diagonally downward from this apex 18d toward the outlet section 18b. This makes it possible to ensure a water pooling area S6 on the upstream side of the curved area S5.

[0026] Next, the operation of the siphon flush toilet 1 according to the present embodiment described above will be explained with reference to FIGS. First, according to the siphon flush toilet 1 of this embodiment, the horizontal region S4 of the external drainage pipe 18 of the drain socket 6 is equipped with a reduced diameter section 26 where the size of the flow path cross section is the smallest in the entire external drainage pipe 18. This allows the reduced diameter portion 26 to reduce the space of the air reservoir A0, thereby preventing, for example, air A0 that flows into the horizontal region S4 of the drain socket 6 from the floor-side drain pipe D side from passing through the reduced diameter portion 26 of the horizontal region S4 and flowing into the connection region S3. In addition, waste w in the drainage flowing down from the vertically descending region S1 of the descending pipe 12d of the drain trap pipe 12 of the toilet body 2 into the connection region S3 of the external drain pipe 18 of the drain socket 6 can fall forcefully from the top 12b of the ascending pipe 12c in the drain trap pipe 12 of the toilet body 2 through the vertically descending region S1 of the descending pipe 12d into the connection region S3 with high potential energy. Therefore, due to the momentum of the waste matter w falling with such force, even if the cross-sectional area of the flow path is reduced by the reduced diameter section 26 of the horizontal region S4, the waste matter w can maintain its momentum along with the flow of wastewater and pass through the horizontal region S4 without clogging. As a result, a siphon action can be reliably generated in the external drainage pipe 18 of the drain socket 6, and clogging with waste w can be prevented.

[0027] Next, with the siphon flush toilet 1 of this embodiment, by reducing the diameter of the reduced diameter section 26 of the horizontal region S4 of the external drainage pipe 18 on the top surface 26a side of the flow path cross section C1, it is possible to reduce the space in the upper flow path within the horizontal region S4 where air pockets A0 occur. Therefore, it is possible to prevent the siphon action from being impaired by the air A0 passing through the external drainage pipe 18 or the air pool A0 in the flow path.

[0028] Furthermore, with the siphon-type flush toilet 1 of this embodiment, even if waste w falls with great potential energy from the top 12b of the rising pipe 12c in the drain trap pipe 12 of the toilet body 2, through the vertical descent region S1 of the descending pipe 12d, and into the connection region S3, and collides with a part of the connection region S3 (such as the step 34), becoming flattened, and is then discharged into the horizontal region S4, the cross-sectional shape of the flow path of the reduced diameter section 26 of the horizontal region S4 is formed in an elliptical shape when viewed from the flow direction of the horizontal region S4, so the flattened waste w can pass smoothly through the elliptical reduced diameter section 26 of the horizontal region S4. Therefore, the discharge performance of the waste w in the horizontal region S4 can be improved.

[0029] Furthermore, with the siphon flush toilet 1 of this embodiment, the intersection Q between the first top surface 22 of the connection area S3 and the second top surface 26a of the horizontal area S4 in the side view shown in Figure 2 is located downstream of the center point O3 of the curvature (curvature radius r1) of the bottom surface 24 of the connection area S3. This allows the cross-sectional area of the flow path on the top surface side of the reduced diameter portion 26 of the horizontal region S4 of the external drainage pipeline 18 to be reduced to the smallest in the entire external drainage pipeline 18.

[0030] Furthermore, with the siphon flush toilet 1 according to this embodiment, the first top surface 22 of the connection area S3 and the second top surface 26a of the reduced diameter section 26 of the horizontal area S4 are connected to each other in a broken line at the intersection Q between the two in the side view shown in Figure 2. It is possible to reduce the space through which the air A0 in the external drainage pipe 18 passes in both directions near both top surfaces 22, 26a from the upstream side to the downstream side or from the downstream side to the upstream side. Therefore, it is possible to prevent the air pocket A0 in the external drainage pipe 18 from impairing the siphon action.

[0031] Furthermore, with the siphon flush toilet 1 of this embodiment, the cross-sectional shape of the flow path in the horizontal region S4 is formed so as to remain roughly uniform from the upstream side to the downstream side, which makes it possible to prevent air pockets A0 and clogging with waste w within the horizontal region S4. Furthermore, a portion of the horizontal region S4 (the ascending portion 28 and the descending portion 30) forms a curved region S5 that curves upward. This makes it possible to ensure a water pooling region S6 on the upstream side of the bent region S5, etc., thereby improving the start-up of the siphon action.

[0032] Furthermore, with the siphon flush toilet 1 of this embodiment, the wall surface 32 on the side of the connection area S3 that faces the first top surface 22 in the front-to-rear direction in a side view is equipped with a step 34, and the top surface 34a of this step 34 is located at a height position that is roughly the same as the height position P1 of the second top surface 26a of the horizontal area S4, or at a height position P2 that is slightly below this height position P1. Additionally, the top surface 34a of the step 34 is located below the flow path cross section C0 of the vertically descending area S1. As a result, the wastewater that flows down from the vertically descending area S1 of the descending pipe 12d of the drain trap pipe 12 of the toilet body 2 into the connection area of the external drain pipe 18 collides with the upper surface of the step from above, and then becomes watertight up to approximately the same height as the second top surface in the horizontal area. Therefore, it is possible to eliminate the space for air to accumulate in the horizontal area, and it is possible to prevent the siphon action from being impaired by air accumulation. [Explanation of symbols]

[0033] 1. Siphon-type flush toilet according to one embodiment of the present invention 2 Toilet body 4. Cleaning water supply device 6 drain socket 8 Toilet bowl 10 Rim of toilet bowl body 12 Toilet body drain trap pipe 12a Inlet of drain trap pipe 12b Top of drain trap line 12c Drain trap pipe riser 12d Downstream pipe of drain trap pipe 12e Outlet of drain trap pipe, outlet of downcomer pipe, outlet of vertical downflow area 14 Rim Spout 16 Jet Spout 18 External drain line 18a Upstream end and inlet of external drainage pipe, inlet of drainage socket 18b Downstream end and outlet of external drainage pipe, outlet of drainage socket 18c Outlet of the connection area of the external drainage line 18d Top of external drainage line 20 Elastic seal connecting member 22 Top surface of the connection area of the external drainage pipe, first top surface 24 Bottom of the connection area of the external drainage line 26. Reducing diameter of external drainage pipe 26a Top surface of the reduced diameter section of the external drainage pipe, second top surface 28 External drainage pipe riser 30 Descending section of external drainage pipe 32 The wall surface facing the first top surface of the connection area in the front-to-rear direction 34 Step part 34a Upper surface of step A0 Air, air pocket A1 Central axis of the outlet of the vertical descending area A2 Center axis of the inlet of the floor-side drain pipe C0 Flow cross section in the vertical downward region C1 Cross section of the flow channel at the narrowed diameter part of the horizontal region D Floor side drain pipe D0 Floor side drain pipe inlet d1: specified distance in the forward and backward direction F Floor O1 Center of the outlet of the vertical downflow region O2 Center of floor drain pipe inlet O3 Center of curvature of the connection area P1 Height position of the second top surface of the horizontal area P2 Height position of the top surface of the step in the connection area Q Intersection of the first and second top surfaces r1 radius of curvature S1 Vertical descending area of the downcomer pipe of the drain trap pipe S2 Upstream area of external drainage pipeline S3 External drainage line connection area S4 Horizontal area of external drain line S5 bending area S6 Water area W1 Rim Spout W2 Jet Water Spout w filth

Claims

1. A siphon-type flush toilet that discharges waste by siphon action, a toilet body including a bowl portion for receiving waste and a drain trap pipe line having an inlet portion connected below the bowl portion; an external drainage pipe provided outside the toilet body and connecting the outlet of the drain trap pipe and the inlet of a floor-side drainage pipe; The drain trap pipe includes an ascending pipe that rises from the downstream side of the inlet portion thereof to a top portion rearward and upward, and a descending pipe that descends rearward and downward from the top portion of the ascending pipe, The down-flow pipe has a vertically descending area that descends vertically from the upstream side to the downstream side outlet, and the center of the outlet of this vertically descending area and the center of the inlet of the floor-side drain pipe are arranged eccentrically to each other, A siphon type flush toilet wherein the external drainage pipeline comprises a connection region connected to the outlet of the vertically descending region, and a horizontal region extending substantially horizontally from the outlet of this connection region and then connecting to the inlet of the floor-side drainage pipe, the horizontal region comprising a reduced diameter section where the size of the flow path cross section is the smallest in the entire external drainage pipeline.

2. 2. The siphon flush toilet according to claim 1, wherein the reduced diameter section is formed by reducing the diameter of the ceiling surface side of the flow path cross section of the horizontal region.

3. 2. The siphon flush toilet according to claim 1, wherein the reduced diameter section has a flow path cross section that is elliptical when viewed from the flow path direction of the horizontal area.

4. The siphon flush toilet of claim 1, wherein the connection area has a first top surface that is formed in a straight line in side view and a bottom surface that is formed in a substantially arc shape, the horizontal area has a second top surface that is connected to the first top surface, and the intersection of the first top surface and the second top surface in side view is located downstream of the center point of curvature of the bottom surface.

5. The siphon flush toilet according to claim 4, wherein the first top surface and the second top surface are connected to each other in a broken line at the intersection point when viewed from the side.

6. The siphon flush toilet according to claim 1, wherein the horizontal region is formed so that its flow path cross-sectional shape remains substantially uniform from the upstream side to the downstream side, while a portion of the horizontal region forms a curved region that bends upward.

7. The siphon flush toilet according to claim 4, wherein the wall surface of the connection area facing the first top surface in a side view has a step portion provided at approximately the same height as the second top surface of the horizontal area, and the upper surface of this step portion is located below the flow path cross section of the vertically descending area.

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