Flow control valve

Abstract

The invention relates to a flow control valve. The purpose of the present invention is to improve mold release properties when forming a sealing member having an undercut portion provided in a flow rate control valve. A flow control valve is provided with: a housing (31) having a passage (33); a valve seat (37) provided midway in the passage (33); a valve body (51) that opens and closes the valve seat (37) by movement in the axial direction; and a sealing member (70) that is provided between the valve seat (37) and the valve body (51) and seals between the valve seat (37) and the valve body (51) when the valve is closed. The seal member (70) has a base section (72) attached to the valve body (51), and a conical cylindrical seal lip (73) protruding from the surface of the base section (72). A recessed portion (74) continuous with the inner peripheral surface of the seal lip (73) is formed on the surface of the base portion (72).

Description

Technical Field

[0001] The technology disclosed in this specification mainly relates to a flow control valve used in an evaporative fuel processing device mounted on a vehicle. Background Art

[0002] In an evaporative fuel processing device, in order to maintain the pressure in a fuel tank in a closed state at an appropriate pressure, there is a device having a positive pressure overflow valve that opens when the pressure in the fuel tank is equal to or higher than a specified positive pressure value and a negative pressure overflow valve that opens when the pressure in the fuel tank is equal to or lower than a specified negative pressure value (see Patent Document 1). In addition, the positive pressure overflow valve in Patent Document 1 corresponds to the flow control valve described in this specification.

[0003] Figure 9 It is a cross-sectional view showing a conventional sealing member. As Figure 9 shown, an annular sealing member 170 made of an elastomer seals with a valve seat member (not shown) when the valve core member 151 closes the valve. The sealing member 170 has: an annular plate-shaped base portion 172 that is mounted on the valve core member 151; and a conical cylindrical sealing lip 173 that protrudes obliquely inward in the axial direction from the surface (the lower surface in Figure 9 ) of the base portion 172. The sealing lip 173 has a substantially constant wall thickness 173T, a lip angle 173θ, a lip center length 173L, and a forced demolding width 173W.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-121791 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] When forming the conventional sealing member 170, the inner peripheral side space portion of the sealing lip 173 becomes an undercut portion 173U. Therefore, forced demolding forming is performed in which the sealing lip 173 is forced to deform and demolded from the mold. However, at the time of demolding, forming defects such as fracture and material shortage are likely to occur in the sealing lip 173, and there is a problem of poor demoldability.

[0009] The problem to be solved by the technology disclosed in this specification is to improve the demoldability when forming a sealing member having an undercut portion provided in a flow control valve.

[0010] Solutions to the Problems

[0011] In order to solve the above problems, the technology disclosed in this specification adopts the following technical solutions.

[0012] The first technical scheme is a flow control valve, which comprises: a shell having a fluid passage; an annular valve seat member, which is arranged in the middle of the passage; a valve core member, which opens and closes the valve seat member by moving in the axial direction; and an annular sealing member composed of an elastomer, which is arranged between the valve seat member and the valve core member and seals the valve seat member and the valve core member when the valve is closed, the sealing member having: an annular base, which is installed on one of the two members; and a conical cylindrical sealing lip, which protrudes obliquely toward the axial inside from the surface of the base, the sealing lip is separated from the other of the two members when the valve core member opens the valve, and elastically contacts the other member when the valve core member closes the valve, wherein an annular recess is formed on the surface of the base, the recess having an inner wall surface continuous with the inner peripheral surface of the sealing lip and continuous in the circumferential direction.

[0013] According to the first technical solution, a circular concave portion is formed on the surface of the base of the sealing member having an undercut portion provided in the flow control valve, and the concave portion has an inner wall surface continuous with the inner peripheral surface of the sealing lip and is continuous in the circumferential direction. Therefore, the lip center length of the sealing lip is extended by an amount corresponding to the depth of the concave portion, and the softness, that is, the flexibility of the sealing lip is improved accordingly. As a result, the demolding property when molding the sealing member can be improved.

[0014] A second invention is a flow control valve according to the first invention, wherein the seal lip is formed in a shape whose cross section becomes narrower from the base end side toward the tip end side.

[0015] According to the second aspect, the mold releasability during molding of the sealing member can be further improved.

[0016] A third invention is the flow control valve according to the first invention or the second invention, wherein the inner wall surface of the recessed portion has a concave curved surface having an arc-shaped cross section that smoothly continues with the inner peripheral surface of the seal lip.

[0017] According to the third aspect, stress generated when the seal lip is deformed can be dispersed, thereby suppressing deterioration of the seal lip.

[0018] A fourth technical solution is a flow control valve according to the third technical solution, wherein the concave curved surface and the surface of the base portion are smoothly connected by a convex curved surface having an arc-shaped cross section.

[0019] According to the fourth aspect, stress generated when the seal lip is deformed can be dispersed, thereby suppressing deterioration of the seal lip.

[0020] Effects of the Invention

[0021] According to the technology disclosed in this specification, it is possible to improve the mold release property when forming a sealing member having an undercut portion provided in a forming flow control valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FIG. is a structural diagram showing an evaporation fuel processing device according to an embodiment.

[0023] Figure 2 FIG. is a cross-sectional view showing an overflow valve device.

[0024] Figure 3 FIG. is a cross-sectional view showing an open valve state of a positive pressure overflow valve of the overflow valve device.

[0025] Figure 4 FIG. is a cross-sectional view showing an open valve state of a negative pressure overflow valve of the overflow valve device.

[0026] Figure 5 FIG. is a bottom view of a first spool member including a sealing member.

[0027] Figure 6 FIG. is Figure 5 a cross-sectional view taken along line VI-VI of FIG.

[0028] Figure 7 FIG. is a cross-sectional view showing a first sealing lip.

[0029] Figure 8 FIG. is a cross-sectional view showing the first sealing lip in a closed valve state.

[0030] Figure 9 FIG. is a cross-sectional view showing a sealing member of a conventional example.

[0031] REFERENCE MARK DESCRIPTION

[0032] 30, overflow valve device; 31, housing; 33, passage; 37, valve seat (valve seat member, another member); 50, positive pressure overflow valve (flow control valve); 51, first spool (spool member, one member); 70, sealing member; 72, base; 72a, lower surface (surface); 73, first sealing lip (sealing lip); 73a, inner peripheral surface; 74, recess; 74a, concave curved surface; 74b, convex curved surface. DETAILED DESCRIPTION OF THE EMBODIMENT

[0033] Hereinafter, an embodiment for implementing the technology disclosed in this specification will be described with reference to the drawings. The flow control valve of this embodiment is configured as a positive pressure overflow valve of an overflow valve device of an evaporation fuel processing device mounted on a vehicle such as an automobile equipped with an internal combustion engine (engine). Therefore, after explaining the outline of the evaporation fuel processing device, the positive pressure overflow valve will be described together with the overflow valve device.

[0034] (Overview of Evaporative Fuel Treatment Device)

[0035] Figure 1 It is a structural diagram showing an evaporative fuel treatment device. As Figure 1 shown, in the evaporative fuel treatment device 10, the evaporative fuel evaporated in the fuel tank 12 is adsorbed by an adsorbent material such as activated carbon in the filter tank 17 via the vapor passage 13. A shut-off valve 14 composed of an electric on-off valve is interposed in the middle of the vapor passage 13. A bypass passage 15 bypassing the shut-off valve 14 is provided in the vapor passage 13. An overflow valve device 30 is interposed in the middle of the bypass passage 15. In addition, the fuel in the fuel tank 12 is supplied to an internal combustion engine (engine) 24 via a fuel supply path 22 by a fuel supply device 20.

[0036] The filter tank 17 is connected to the intake passage 26 of the internal combustion engine 24 via a purge passage 18. A purge valve 19 is interposed in the middle of the purge passage 18. During the operation of the internal combustion engine 24, when the purge valve 19 is opened at a specified time, the evaporative fuel in the filter tank 17 is supplied to the intake passage 26 via the purge passage 18 by the intake negative pressure of the internal combustion engine 24. In addition, the shut-off valve 14 and the purge valve 19 are controlled to open and close by an engine control unit (hereinafter referred to as "ECU") 28.

[0037] In addition, during vehicle parking, the shut-off valve 14 is maintained in a closed state, so that the vapor passage 13 is cut off. Therefore, the evaporative fuel in the fuel tank 12 does not flow into the filter tank 17. In addition, during fuel supply, the vapor passage 13 is connected by opening the shut-off valve 14, so that the evaporative fuel in the fuel tank 12 is adsorbed by the adsorbent material in the filter tank 17 via the vapor passage 13. In addition, when the shut-off valve 14 is closed during vehicle parking or the like, the pressure in the fuel tank 12 is maintained at an appropriate pressure by the overflow valve device 30.

[0038] (Overflow Valve Device 30)

[0039] Figure 2 It is a cross-sectional view showing the overflow valve device 30. Regarding the overflow valve device 30, the up-down direction and the left-right direction are defined, but the arrangement direction of the overflow valve device 30 is not specified. As Figure 2 shown, the overflow valve device 30 includes a housing 31, a positive pressure overflow valve 50, and a negative pressure overflow valve 60. The overflow valve device 30 is preferably arranged such that the axis direction points vertically with respect to the vehicle. Figure 2 shown, the overflow valve device 30 includes a housing 31, a positive pressure overflow valve 50, and a negative pressure overflow valve 60. The overflow valve device 30 is preferably arranged such that the axis direction points vertically with respect to the vehicle.

[0040] (Housing 31)

[0041] The housing 31 has a housing main body 32, a cover 40, and a retaining member 42. The internal space of the housing 31 forms a fluid passage 33. The housing main body 32 is formed of a resin material into a bottomed cylindrical shape. A first communication port 34 communicating with the passage 33 is formed at the center of the bottom wall of the housing main body 32. A second communication port 35 communicating with the passage 33 is formed in the side wall of the housing main body 32.

[0042] The first communication port 34 is connected to the fuel tank 12 via the passage portion on the fuel tank 12 side of the bypass passage 15 of the evaporative fuel processing device 10 (refer to Figure 1 ) and the vapor passage 13. The second communication port 35 is connected to the canister 17 via the passage portion on the canister 17 side of the bypass passage 15 of the evaporative fuel processing device 10 (refer to Figure 1 ).

[0043] A ring plate-shaped valve seat 37 is concentrically arranged on the bottom wall of the housing main body 32. The valve seat 37 is formed of a metal material and is integrated with the bottom wall portion by insert molding. The valve seat 37 corresponds to the "valve seat member" and "another member" described in this specification.

[0044] The cover 40 is formed of a resin material into a cap shape. The cover 40 closes the upper end opening of the housing main body 32. In addition, the retaining member 42 is formed of a resin material into a circular ring shape. The retaining member 42 is joined to the upper end portion of the side wall of the housing main body 32 and the outer periphery of the cover 40 by welding or the like.

[0045] (Positive pressure overflow valve 50)

[0046] The positive pressure overflow valve 50 is assembled concentrically in the housing 31. The positive pressure overflow valve 50 opens and closes the valve seat 37 by moving in the axial direction (up and down direction). That is, the positive pressure overflow valve 50 is normally closed and opens when the pressure on the first communication port 34 side, that is, the fuel tank 12 side, becomes equal to or higher than the opening pressure on the positive pressure side. In Figure 2 , the positive pressure overflow valve 50 and the negative pressure overflow valve 60 are shown in a closed state. The positive pressure overflow valve 50 corresponds to the "flow control valve" described in this specification.

[0047] The valve element (referred to as "first valve element") 51 of the positive pressure overflow valve 50 is arranged so as to be movable in the housing 31 in the axial direction, that is, the up and down direction. The first valve element 51 has a ring plate-shaped first valve plate portion 51a and an inner and outer double-layer cylindrical shaft portion 51b and cylindrical portion 51c formed concentrically on the first valve plate portion 51a. The first valve element 51 corresponds to the "valve element member" and "one member" described in this specification.

[0048] The first valve plate portion 51a has an outer diameter smaller than the inner diameter of the side wall of the housing body 32. The first valve plate portion 51a has an outer diameter larger than the outer diameter of the cylindrical portion 51c. When the first valve element 51 closes the valve, the first valve plate portion 51a (specifically, the outer peripheral portion) closes the valve seat 37 of the housing 31 by means of the sealing member 70. A plurality of (two are shown in Figure 2 the) communication holes 52 penetrating in the plate thickness direction (vertical direction) are formed in the first valve plate portion 51a. The communication holes 52 are arranged around the shaft portion 51b. The height of the shaft portion 51b is higher than the height of the cylindrical portion 51c.

[0049] The first spring 55 formed of a helical spring is concentrically interposed between the first valve plate portion 51a and the cover 40. The first spring 55 biases the first valve element 51 downward, i.e., in the closing direction. The lower end portion of the first spring 55 is arranged adjacent to the inner peripheral surface of the cylindrical portion 51c of the first valve element 51.

[0050] The upper surface of the valve seat 37 and the lower surface of the first valve plate portion 51a of the first valve element 51 are opposing flat surfaces. A ring-shaped sealing member 70 is mounted on the lower surface of the first valve plate portion 51a. The sealing member 70 will be described later.

[0051] (Negative pressure overflow valve 60)

[0052] The negative pressure overflow valve 60 is assembled concentrically with the positive pressure overflow valve 50 in the housing 31. The negative pressure overflow valve 60 opens and closes with the first valve plate portion 51a of the first valve element 51 as the valve seat by moving in the axial direction (vertical direction). That is, the negative pressure overflow valve 60 is normally closed and opens when the pressure on the fuel tank 12 side becomes equal to or lower than the opening pressure on the negative pressure side.

[0053] For the valve element (referred to as "second valve element") 61 of the negative pressure overflow valve 60, the second valve element 61 concentrically has an annular plate-shaped second valve plate portion 61a and a hollow valve shaft portion 61b protruding from the inner peripheral portion of the second valve plate portion 61a. The valve shaft portion 61b is arranged so as to be able to move in the axial direction, i.e., the vertical direction, within the shaft portion 51b of the first valve element 51. A ring-shaped spring support member 62 is mounted on the top end portion (upper end portion) of the valve shaft portion 61b.

[0054] The second valve plate portion 61a has an outer diameter smaller than the inner diameter of the first communication port 34. When the second valve element 61 closes the valve, the second valve plate portion 61a closes the first valve plate portion 51a of the first valve element 51 (specifically, the portion surrounding the plurality of communication holes 52) by means of the sealing member 70.

[0055] The second spring 65 formed of a helical spring is concentrically interposed between the spring support member 62 and the first valve plate portion 51a. The lower end portion of the second spring 65 is disposed at a portion of the first valve element 51 that surrounds the plurality of communication holes 52. The second spring 65 biases the second valve element 61 upward, i.e., in the closing direction. The second spring 65 has a biasing force smaller than that of the first spring 55.

[0056] (Operation of the overflow valve device 30)

[0057] Now, it is assumed that the shut-off valve 14 provided in the evaporative fuel processing device 10 (see Figure 1 ) is in the closed state, and the two overflow valves 50 and 60 of the overflow valve device 30 are in the closed state (see Figure 2 ). That is, the first valve plate portion 51a of the first valve element 51 is seated on the valve seat 37 by means of the sealing member 70 under the biasing force of the first spring 55. Further, the second valve plate portion 61a of the second valve element 61 is seated on the first valve element 51 by means of the sealing member 70 under the biasing force of the second spring 65. Thereby, the passage 33 is cut off.

[0058] In this state, when a positive pressure higher than the opening pressure is generated on the fuel tank 12 side, the positive pressure overflow valve 50 opens. That is, as shown in Figure 3 , the first valve element 51 rises, i.e., opens, against the biasing force of the first spring 55. At this time, the sealing member 70 separates from the valve seat 37, and thus the passage 33 is opened. Therefore, the fluid from the fuel tank 12 side flows toward the canister 17 side through the passage 33 (see the arrow in Figure 3 ). Thereby, the pressure in the fuel tank 12 is reduced.

[0059] Further, when a negative pressure lower than the opening pressure of the negative pressure overflow valve 60 is generated on the fuel tank 12 side, the negative pressure overflow valve 60 opens. That is, as shown in Figure 4 , the second valve element 61 descends, i.e., opens, against the biasing force of the second spring 65. At this time, the second valve plate portion 61a of the second valve element 61 separates from the sealing member 70, and thus the passage 33 is opened through the communication holes 52. Therefore, the fluid from the canister 17 side flows toward the fuel tank 12 side through the passage 33 including the communication holes 52 (see the arrow in Figure 4 ). Thereby, the pressure in the fuel tank 12 rises.

[0060] (Sealing member 70)

[0061] Figure 5 is a bottom view showing the first valve element 51 provided with the sealing member, Figure 6 is Figure 5 a sectional view taken along the viewing direction of the VI-VI line of Figure 6As shown, the sealing member 70 is integrally formed and mounted on the lower surface of the first valve plate portion 51a of the first valve element 51. The sealing member 70 is made of a rubber-like elastomer. Engagement portions 71a and 71b that engage with a plurality of (two are shown in Figure 6 ) engagement holes 53a and 53b formed in the first valve plate portion 51a are formed in the inner peripheral portion and the outer peripheral portion of the upper surface of the sealing member 70.

[0062] The sealing member 70 has an annular plate-shaped base portion 72, a first sealing lip 73 formed on the outer peripheral portion of the lower surface 72a of the base portion 72, and a second sealing lip 77 formed on the inner peripheral portion of the lower surface 72a of the base portion 72 (see Figure 5 ). The upper surface of the base portion 72 is mounted on the lower surface of the first valve plate portion 51a of the first valve element 51. The lower surface 72a of the base portion 72 corresponds to the "surface" referred to in this specification. The first sealing lip 73 will be described after the second sealing lip 77.

[0063] The second sealing lip 77 is formed in a conical cylinder shape that protrudes obliquely inward in the axial direction from the inner peripheral portion of the lower surface of the base portion 72. A protrusion 77a having a triangular cross-section is formed in an annular shape on the outer peripheral surface of the second sealing lip 77.

[0064] When the second valve element 61 closes the valve (see Figure 2 ), the second valve plate portion 61a elastically contacts and fits with the tip portion of the second sealing lip 77 of the sealing member 70 including the protrusion 77a. Thereby, the space between the second valve element 61 and the first valve element 51 is sealed. Further, when the second valve element 61 opens the valve (see Figure 4 ), the second valve plate portion 61a separates from the second sealing lip 77 of the sealing member 70, and thus the second sealing lip 77 elastically returns to its original state.

[0065] (The first sealing lip 73)

[0066] Figure 7 is a cross-sectional view showing the first sealing lip 73. As Figure 7 shown, the first sealing lip 73 is formed in a conical cylinder shape that protrudes obliquely inward in the axial direction from the outer peripheral portion of the lower surface of the base portion 72. The first sealing lip 73 corresponds to the "sealing lip" referred to in this specification.

[0067] The first sealing lip 73 is formed in a shape that tapers from the base end side toward the tip end side. That is, the wall thickness 73T of the first sealing lip 73 becomes smaller from the base end side toward the tip end side. The tip end portion of the first sealing lip 73 is rounded.

[0068] The first sealing lip 73 has an inner peripheral surface 73a that forms an acute angle with the lower surface 72a of the base 72. The angle formed by the lower surface 72a and the inner peripheral surface 73a is defined as the lip angle 73θ. The sealing lip 73 has a lip center length 73L and a forced demolding width 73W. When forming the sealing member 70, the inner peripheral side space portion of the sealing lip 73 becomes an undercut portion 70U.

[0069] A circular concave portion 74 is formed on the lower surface 72a of the base 72. The concave portion 74 has an inner wall surface that is continuous with the inner peripheral surface 73a of the first sealing lip 73 and is continuous in the circumferential direction. The inner wall surface of the concave portion 74 has a concave curved surface 74a with a circular arc-shaped cross section that is smoothly continuous with the inner peripheral surface 73a of the first sealing lip 73. The concave curved surface 74a and the lower surface 72a of the base 72 are smoothly continuous by a convex curved surface 74b with a circular arc-shaped cross section.

[0070] When the first valve element 51 closes the valve, the tip of the first sealing lip 73 elastically contacts and fits with the upper surface of the valve seat 37 (see Figure 8 ). At this time, the first sealing lip 73 is elastically deformed so as to tilt radially inward and upward. Thereby, the space between the first valve element 51 and the valve seat 37 is sealed. When the first valve element 51 opens the valve, the first sealing lip 73 separates from the valve seat 37, and thus the first sealing lip 73 elastically returns to its original state (see Figure 7 ).

[0071] (Advantages of an embodiment)

[0072] According to this embodiment, a circular concave portion 74 is formed on the lower surface 72a of the base 72 of the sealing member 70 having an undercut portion 70U provided in the positive pressure relief valve 50. The concave portion 74 has an inner wall surface that is continuous with the inner peripheral surface 73a of the first sealing lip 73 and is continuous in the circumferential direction. Therefore, compared with the lip center length 173L of the sealing lip 173 in the conventional example (see Figure 9 ), the lip center length 73L of the first sealing lip 73 is extended by an amount corresponding to the depth of the concave portion 74. Correspondingly, the flexibility, that is, the flexibility of the first sealing lip 73 is improved. Thereby, the demolding property when forming the sealing member 70 can be improved.

[0073] In addition, the first sealing lip 73 is formed in a shape that tapers in cross section from the base end side toward the tip end side. Thereby, the demolding property when forming the sealing member 70 can be further improved. Here, the wall thickness 73T of the tip of the first sealing lip 73 is set to be equal to the wall thickness 173T of the sealing lip 173 in the conventional example (see Figure 9 ) and gradually increases toward the base end portion. Therefore, compared with the sealing lip 173 in the conventional example, the elasticity of the base end portion side of the first sealing lip 73 can be increased and the flexibility, that is, the flexibility of the tip end portion side can be improved.

[0074] In addition, the lip angle 73θ of the first sealing lip 73 is set to be approximately 20° larger than the lip angle 173θ of the sealing lip 173 in the conventional example (refer to Figure 9 ). This is effective in improving the mold release property when forming the sealing member 70.

[0075] In addition, the forced mold release width 73W of the first sealing lip 73 is set to be slightly smaller than the forced mold release width 173W of the sealing lip 173 in the conventional example. This is effective in improving the mold release property when forming the sealing member 70.

[0076] In addition, the inner wall surface of the recess 74 has a concave curved surface 74a with a circular arc cross-section that is smoothly continuous with the inner peripheral surface 73a of the first sealing lip 73. Thereby, the stress when the first sealing lip 73 deforms can be dispersed, and deterioration of the first sealing lip 73 can be suppressed.

[0077] In addition, the inner wall surface of the recess 74 and the lower surface 72a of the base portion 72 are smoothly continuous with a convex curved surface 74b having a circular arc cross-section. Thereby, the stress when the first sealing lip 73 deforms can be dispersed, and deterioration of the first sealing lip 73 can be suppressed.

[0078] [Other Embodiments]

[0079] The technology disclosed in this specification is not limited to the above-described embodiments, but can be implemented in various other ways. For example, the technology disclosed in this specification is not limited to the positive pressure overflow valve 50 of the evaporative fuel processing device 10, and can also be applied to the negative pressure overflow valve 60 and the overflow valves of other devices. In addition, instead of being mounted on the first valve element 51, the portion including the first sealing lip 73 of the sealing member 70 can be mounted on the valve seat 37. In addition, the base portion 72 of the sealing member 70 can also be mounted on the first valve plate portion 51a of the first valve element 51 by bonding, welding, etc. In addition, the cross-sectional shape of the recess 74 of the sealing member 70 can also be appropriately changed.

Claims

1. A flow control valve comprising: a housing having a passage for a fluid; a circular valve seat member disposed midway in the passage; a valve core member that opens and closes the valve seat member by moving in the axial direction; and An annular sealing member made of an elastic body is provided between the valve seat member and the valve core member and seals the valve seat member and the valve core member when the valve is closed. The sealing member includes: an annular base portion mounted on one of the two members; and a conical cylindrical sealing lip protruding obliquely toward the axial inner side from the surface of the base portion. The sealing lip is separated from the other of the two components when the valve core component opens the valve, and elastically contacts the other component when the valve core component closes the valve, wherein: An annular recessed portion is formed on the surface of the base portion. The recessed portion has an inner wall surface that is continuous with the inner peripheral surface of the seal lip and is continuous in the circumferential direction.

2. The flow control valve according to claim 1, wherein: The seal lip is formed in a shape whose cross section becomes narrower from the base end side toward the tip end side.

3. The flow control valve according to claim 1 or 2, wherein: The inner wall surface of the recessed portion has a concave curved surface having an arc-shaped cross section that smoothly continues with the inner peripheral surface of the seal lip.

4. The flow control valve according to claim 3, wherein: The concave curved surface and the surface of the base portion are smoothly connected by a convex curved surface having an arc-shaped cross section.

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