Pressure relief valve

Abstract

This provides a pressure relief valve that allows for stable mounting of the coil spring and minimizes variations in performance between individual products. [Solution] One embodiment is a pressure relief valve (100) comprising a movable valve body (130) for opening and closing a fluid passage, and a coil spring (110) for biasing the valve body (130) in the closing direction. The valve body (130) has a load-bearing surface (145) on which the coil spring (110) sits, a guide wall surface (142) extending from the load-bearing surface (145) in the axial direction of the coil spring, and at least one recess (144) formed in the load-bearing surface (145) at the corner formed by the load-bearing surface (145) and the guide wall surface (142).

Description

Technical Field

[0001] The technology disclosed in the present application relates to a pressure relief valve.

Background Art

[0002] A valve may be provided for pressure relief in a closed system such as a sealed tank. Japanese Unexamined Patent Application Publication No. 2016-121791 discloses a pressure relief valve provided in a vent passage that leads from a fuel tank to the atmosphere in a vehicle equipped with an engine, for controlling the internal pressure of the fuel tank. This pressure relief valve includes two valve bodies. When the internal pressure of the fuel tank reaches a negative pressure of a predetermined magnitude, one valve body opens, and when it reaches a positive pressure of a predetermined magnitude, the other valve body opens, thereby maintaining the internal pressure appropriately.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, pressure relief valves are often required to have strict performance of reliably opening in a high-pressure range while suppressing leakage in a low-pressure range. To meet this requirement, it is necessary for the coil spring to be seated in a stable posture at a predetermined position. Therefore, there is a need for a pressure relief valve that can stably attach the coil spring and suppress variations in performance among products.

Means for Solving the Problems

[0005] One aspect of this technology is a pressure relief valve comprising a movable valve body for opening and closing a fluid passage, and a coil spring for biasing the valve body in the closing direction. The valve body has a load-bearing surface on which the coil spring sits, a guide wall surface extending axially from the load-bearing surface in the direction of the coil spring, and at least one recess formed on the load-bearing surface at the corner formed by the load-bearing surface and the guide wall surface. By designing the load-bearing surface to be thinned in advance at the corner, the formation of a curved surface during molding can be avoided. Therefore, variations in the biasing force on the valve body due to the coil spring riding up onto the curved surface can be suppressed.

[0006] In some embodiments, each of the at least one recess is connected to the load-bearing surface by a curved surface. This makes it possible to suppress the formation of steps on the load-bearing surface when forming the recesses.

[0007] In some embodiments, each of the at least one recess is linearly connected to the guide wall surface. This makes it possible to avoid the formation of steps at the corners when forming the recesses.

[0008] In some embodiments, the guide wall surface has at least one projection extending in the axial direction. This restricts the movement of the coil spring perpendicular to the axis when the pressure relief valve is in use, thereby suppressing variations in the biasing force applied to the valve body.

[0009] In some embodiments, each of the at least one recess is provided corresponding to one of the at least one protrusions.

[0010] In some embodiments, the at least one protrusion is three or more protrusions. This effectively aligns the coil spring and suppresses variations in the biasing force applied to the valve body.

[0011] In some embodiments, the three or more protrusions are arranged in an odd number, avoiding each other's opposing positions. This makes assembly easier, even when press-fitting is required to assemble the coil spring into the inside of the guide wall, because there is space for the tightening force to escape at the opposing positions of each protrusion. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view showing a pressure relief valve in a closed state as one embodiment. [Figure 2] This is a cross-sectional view of a pressure relief valve that provides positive pressure relief for a tank. [Figure 3] This is a cross-sectional view of a pressure relief valve that provides negative pressure relief for a tank. [Figure 4] This is a plan view showing a valve body for positive pressure relief, displayed separately. [Figure 5] Figure 4 is a cross-sectional view of the valve body along the VV line. [Figure 6] This is a perspective view showing the protrusions on the guide wall and the recesses on the load-bearing surfaces at the corners. [Figure 7] This is a perspective view of a coil spring, whose ends have been flattened by grinding, seen from a diagonal downward angle. [Figure 8] This is an enlarged cross-sectional view of the protrusions on the guide wall and the recesses on the load-bearing surface. [Figure 9] This is a cross-sectional view showing a curved surface formed at a corner and a coil spring riding on it, when no recess is provided on the load-bearing surface. [Figure 10] This is a diagram illustrating the configuration of a fuel tank system equipped with a pressure relief valve, as one embodiment of the system. [Modes for carrying out the invention]

[0013] Various embodiments of this technology will be described below with reference to the drawings.

[0014] [Pressure relief valve] FIG. 1 shows a pressure relief valve 100 as one embodiment. The pressure relief valve 100 has a bidirectional pressure relief function. Hereinafter, assuming that one side of the pressure relief valve 100 communicates with some tank not shown in the figure and the other side communicates with the atmosphere, the pressure relief valve 100 capable of performing positive pressure relief and negative pressure relief of the tank will be described.

[0015] The pressure relief valve 100 has a housing 101 that forms a valve chamber. The housing 101 has a tank side port 103 and an atmosphere side port 104, and the valve chamber and these ports form a fluid passage through which the fluid passes through the pressure relief valve 100. The housing 101 can be composed of two divided members. The pressure relief valve 100 includes a valve body 130 for positive pressure relief and a valve body 150 for negative pressure relief that are independently axially movable within the valve chamber. Since the valve body 130 for positive pressure relief is generally disposed outside the valve body 150 for negative pressure relief, hereinafter, the former will also be referred to as the outer valve body 130 and the latter as the inner valve body 150.

[0016] [Valve body for positive pressure relief] As shown in FIGS. 1 and 2, the outer valve body 130 for positive pressure relief has a plate portion 138 with a through hole 143 near the center. The housing 101 has a valve seat 102 formed of a metal annular plate member embedded around the tank side port 103. The outer peripheral portion of the plate portion 138 faces the valve seat 102. When the valve body 130 moves upward (together with the inner valve body 150) and separates from the valve seat 102, the fluid passage is opened (FIG. 2). When the valve body 130 moves downward and adheres to the valve seat 102, the fluid passage is closed (FIG. 1).

[0017] The valve body 130 is biased in the closing direction (downward) with respect to the housing 101 by a coil spring 110. The coil spring 110 is disposed inside an outer cylinder portion 140 extending axially from the plate portion 138 of the valve body 130 and is held between the plate portion 138 and the housing 101.

[0018] The valve body 130 includes an annular seal member 163 made of an elastic material such as rubber or elastomer, which is fixed to the lower side of the plate portion 138 by insert molding or adhesion. The seal member 163 has an annular seal portion 165 that protrudes toward the valve seat 102. When the valve body 130 is closed, the annular seal portion 165 is in close contact with the valve seat 102 by the biasing force of the coil spring 110 to seal the gap.

[0019] [Valve body for negative pressure relief] As shown in FIGS. 1 and 3, the inner valve body 150 for negative pressure relief has a plate portion 156 and a shaft portion 157 that extends axially from the plate portion 156. The shaft portion 157 of the valve body 150 is inserted into the through hole 143 of the plate portion 138 of the outer valve body 130 and is slidably fitted into the inner cylinder portion 139 that extends axially from the inner peripheral portion of the plate portion 138. The inner peripheral portion of the plate portion 138 of the outer valve body 130 functions as the valve seat for the inner valve body 150 and faces the plate portion 156 of the inner valve body 150. When the inner valve body 150 moves downward and the plate portion 156 moves away from the outer valve body 130, the through hole 143 (and thus the fluid passage) is opened (FIG. 3). When the inner valve body 150 moves upward and the plate portion 156 comes into close contact with the outer valve body 130, the through hole 143 is closed (FIG. 1).

[0020] The inner valve body 150 is biased in the closing direction (upward) with respect to the outer valve body 130 by a second coil spring 120 disposed inside the aforementioned coil spring 110. The second coil spring 120 is disposed outside the inner cylinder portion 139 of the outer valve body 130 and is specifically held between a flange-shaped spring receiving portion 159 provided around the shaft portion 157 and the plate portion 138 of the outer valve body 130.

[0021] The seal member 163 provided on the outer valve body 130 has a second annular seal portion 164 that protrudes toward the plate portion 156 of the inner valve body 150 inside the aforementioned annular seal portion 165. When the inner valve body 150 is closed, the plate portion 156 is in close contact with this inner annular seal portion 164 by the biasing force of the inner coil spring 120 to seal the gap.

[0022] [Operation of the pressure relief valve] If the internal pressure on the tank side becomes excessively high (relative to the pressure on the open side), the outer valve body 130 of the pressure relief valve 100 rises against the outer coil spring 110, the outer annular seal portion 165 separates from the valve seat 102, and the fluid passage is opened (Figure 2). As a result, the positive pressure inside the tank is relieved until the outer valve body 130 closes again. If the internal pressure on the tank side drops excessively low, the inner valve body 150 of the pressure relief valve 100 descends against the inner coil spring 120, the plate portion 156 of the inner valve body 150 separates from the inner annular seal portion 164, and the fluid passage is opened (Figure 3). As a result, the negative pressure inside the tank is relieved until the inner valve body 150 closes again.

[0023] [Load-bearing surface] As shown in Figures 6 and 8, the outer coil spring 110 for positive pressure relief is positioned inside the outer cylinder portion 140 extending from the plate portion 138 of the valve body 130, and is held between the plate portion 138 and the housing 101. The upper surface of the plate portion 138 has a load-bearing surface 145 on which the coil spring 110 sits. On the other hand, as shown in Figure 7, the end of the coil spring 110 adjacent to the load-bearing surface 145 is made into a plane 112 perpendicular to the axis by polishing or grinding. The cross-section of the coil of the coil spring 110 gradually decreases towards the end 111, becoming, for example, less than a semicircle at the end 111.

[0024] [Protrusions on the guide wall] As shown in Figures 4-6 and 8, the inner wall surface of the outer cylinder portion 140 has a guide wall surface 142 extending axially from the load-receiving surface 145. The guide wall surface 142 has at least one, for example, three or more, protrusions 141 extending axially from the coil spring 110. This restricts the movement of the coil spring 110 in a direction perpendicular to the axis when the pressure relief valve 100 is in use, and suppresses variations in the biasing force on the valve body 130. The presence of three or more protrusions 141 effectively aligns the coil spring 110. The three protrusions 141 are arranged so as not to be at opposite pole positions from each other. For example, the three protrusions 141 can be arranged at angles of 120 degrees apart. This makes assembly easier, even when press-fitting is required when assembling the coil spring 110 into the outer cylinder portion 140, because there is a place for the tightening force to escape at the opposite pole positions of each protrusion 141. Therefore, the fitting tolerance between the coil spring 110 and the outer cylinder portion 140 can be set to an intermediate fit. In another embodiment not shown, it is also possible to provide five or more odd-numbered protrusions and arrange them while avoiding opposite pole positions (for example, at equal angles).

[0025] [Recess in the load-bearing surface] A corner is formed between the load-bearing surface 145 of the plate portion 138 and the guide wall surface 142 of the outer cylinder portion 140. The load-bearing surface 145 has at least one recess 144 at this corner. In one embodiment, each recess 144 is provided corresponding to a protrusion 141 (Figure 4). For example, it can be a curved groove arranged on the load-bearing surface 145 so as to surround the protrusion 141. By designing the corner of the valve body 130 to be thinned in advance in this way, it is possible to avoid the formation of a curved surface 149 as shown in Figure 9 at the corner during the molding of the valve body 130. Therefore, it is possible to suppress variations in the biasing force on the valve body 130 caused by the edge portion 113 of the part near the end 111 of the coil spring 110 (for example, having a crescent-shaped cross section) riding up onto the curved surface 149. In addition, the sealing performance of the sealing member 163 is improved.

[0026] As shown in Figure 6, each recess 144 is connected to the load-bearing surface 145 by a curved surface. This prevents the formation of steps on the load-bearing surface 145 when forming the recess 144. On the other hand, each recess 144 is connected linearly to the guide wall surface 142 (including the surface of the protrusion 141) in the axial direction of the outer cylinder portion 140. This prevents the formation of steps at the corners when forming the recess 144. The axial length of the protrusion 141 can be set to a length that does not affect the expansion and contraction of the effective winding portion of the coil spring 110. At the upper end of the protrusion 141, a slope 141a can be provided such that the protrusion height decreases toward the inner wall surface of the portion without the protrusion 141. This makes it easier to assemble the coil spring 110.

[0027] In another embodiment (not shown), an annular groove can be provided around the entire circumference of the circular corner formed by the load-receiving surface 145 and the guide wall surface 142.

[0028] In yet another embodiment (not shown), if the end of the inner coil spring 120 for negative pressure relief has a flat surface due to grinding or the like, the same features as described above can be applied to the corner where the coil spring 120 is positioned. That is, a similar projection can be provided on the outer guide wall surface (Figure 5) of the inner cylinder portion 139 of the valve body 130, and a similar recess can be provided on the load-receiving surface 147 (Figure 5) of the plate portion 138 of the valve body 130 on which the coil spring 120 sits.

[0029] [Fuel Tank System] As shown in Figure 10, in one embodiment, the pressure relief valve 100 can be used in a fuel tank system 212 of a vehicle such as an automobile. The fuel tank system 212 includes a fuel tank 215 that stores fuel for supplying to the engine, and the pressure relief valve 100 performs both positive pressure relief and negative pressure relief functions for this fuel tank 215. The fuel in the fuel tank 215 is pumped out by a fuel pump (not shown), supplied through a supply passage 224, and injected into the engine's intake passage by an injector (not shown).

[0030] The fuel tank system 212 is equipped with a canister 243 that collects evaporated fuel (vapor) generated in the fuel tank 215 by adsorbing it with an adsorbent such as activated carbon. The gas phase of the fuel tank 215 communicates with the canister 243 via a vapor passage 231, and the canister 243 communicates with the atmosphere via an atmospheric passage 242. When the pressure inside the fuel tank 215 increases, evaporated fuel moves through the vapor passage 231 and is collected in the canister 243.

[0031] [Tank sealing valve] A tank sealing valve 252 is positioned in the vapor passage 231. The tank sealing valve 252 suppresses the amount of evaporated fuel adsorbed onto the canister 243 by sealing (sealing) the fuel tank as needed. The fuel tank 215 becomes sealed when the fuel filler opening (end opening of the inlet pipe) is closed with a cap and the vapor passage 231 is blocked by the tank sealing valve 252.

[0032] Although not shown in the diagram, the tank sealing valve 252 is configured such that the vapor passage 231 opens when the valve body moves away from the valve seat formed in the housing, and closes when the valve body makes close contact with the valve seat. The tank sealing valve 252 may be equipped with a motor, and the rotation of the motor may be converted into linear motion of the valve body by the screw action of a screw shaft and nut. The tank sealing valve 252 is controlled by a control device 245, such as an ECU, which is electrically connected to the motor.

[0033] The tank sealing valve 252 can also be configured, for example, as described in Japanese Patent Application Publication No. 2018-105307, in which the valve body is supported by one end of a coil spring, and the sealing pressure can be adjusted by changing the position of the other end of the coil spring with a motor. Specifically, when the internal pressure of the fuel tank 215 is lower than the sealing pressure, the valve body is held in the closed position by the biasing force of the coil spring, and when the internal pressure of the fuel tank 215 (more precisely, the pressure relative to the canister side) increases and exceeds the sealing pressure, the valve body moves against the coil spring, and the vapor passage 231 is opened. A sealing pressure of zero corresponds to forcibly holding the tank sealing valve 252 in the open state.

[0034] The canister 243 is connected to the downstream side of the throttle valve in the intake passage via a purge passage 232. While the vehicle is running or idling, the tank sealing valve 252 can be closed at a low sealing pressure or left open to purge the canister 243 as needed. Specifically, by opening the purge valve located in the purge passage 232, the engine's intake negative pressure is applied to the inside of the canister 243. As a result, air is drawn into the canister 243 from the atmosphere through the atmospheric passage 242, and fuel molecules adsorbed on the canister 243 are detached. The detached fuel vapor is taken into the intake passage along with the air and is ultimately burned in the engine. When the engine is stopped, the tank sealing valve 252 can be switched to a high sealing pressure to suppress the adsorption of evaporated fuel onto the canister 243.

[0035] [Function of pressure relief valve] The fuel tank system 212 has a bypass passage 290 that bypasses the tank sealing valve 252. The aforementioned pressure relief valve 100 is located in this bypass passage 290 to relieve any excess positive or negative pressure that may occur in the sealed fuel tank 215. Therefore, the tank-side portion of the bypass passage 290 is connected to somewhere in the vapor passage 231 upstream of the tank sealing valve 252 (for example, the inlet passage within the housing of the tank sealing valve 252). Similarly, the canister-side portion of the bypass passage 290 is connected to somewhere in the vapor passage 231 downstream of the tank sealing valve 252 (for example, the outlet passage within the housing of the tank sealing valve 252).

[0036] The tank sealing valve 252 may fail to open. In this case, if the internal pressure of the fuel tank 215 becomes excessively high (relative to the pressure on the canister 243 side), the outer valve body 130 of the pressure relief valve 100 separates from the valve seat 102, and the bypass passage 290 opens (Figure 2). This relieves the positive pressure inside the fuel tank 215 until the outer valve body 130 closes again. If a sealing pressure is set for the tank sealing valve 252 when it is closed, the opening pressure for positive pressure relief of the pressure relief valve 100 can be set to, for example, the same as or greater than the maximum sealing pressure of the tank sealing valve 252.

[0037] The tank sealing valve 252 cannot relieve the negative pressure in the fuel tank 215 unless it is held open. If the internal pressure of the fuel tank 215 drops excessively, the inner valve body 150 of the pressure relief valve 100 separates from the inner annular seal portion 164, and the bypass passage 290 opens (Figure 3). As a result, the negative pressure in the fuel tank 215 is relieved until the inner valve body 150 closes again.

[0038] Although various embodiments have been described above, this technology is not limited to those embodiments, and those skilled in the art can make various modifications, substitutions, and improvements. [Explanation of symbols]

[0039] 100 Pressure relief valve 101 Housing 102 valve seats 103 Tank-side port 104 Atmospheric side port 110 Outer coil spring 111 Termination 112 plane 113 Edge section 120 Inner coil spring 130 Valve body for positive pressure relief (outside) 138 Board part 139 Inner cylinder 140 Outer cylinder part 141 Projection 141a Slope 142 Guide wall 143 Through hole 144 recess 144a Curved surface 145 Load-bearing surface 146 Guide wall 147 Load-bearing surface 149 Curved surface formed at the corner 150 Negative pressure relief valve body (internal) 156 Board part 157 Shaft 159 Spring support 163 Sealing member 164, 165 Annular seal section 212 Fuel Tank System 215 Fuel Tank 224 Supply passage 231 Vapor Passage 232 Purge Passage 242 Atmospheric passage 243 Canister 245 Control device 252 Tank sealing valve 290 Bypass Passage

Claims

1. It is a pressure relief valve, A movable valve body that opens and closes a fluid passage, The valve body is equipped with a coil spring that biases it in the closing direction. The valve body is a pressure relief valve having a load-bearing surface on which the coil spring sits, a guide wall surface extending from the load-bearing surface in the axial direction of the coil spring, and at least one recess formed on the load-bearing surface at the corner formed by the load-bearing surface and the guide wall surface.

2. A pressure relief valve according to claim 1, wherein each of the at least one recess is connected to the load-receiving surface by a curved surface.

3. A pressure relief valve according to claim 1, wherein each of the at least one recess is linearly connected to the guide wall surface.

4. A pressure relief valve according to any one of claims 1 to 3, wherein the guide wall surface has at least one projection extending in the axial direction.

5. A pressure relief valve according to claim 4, wherein each of the at least one recess is provided corresponding to one of the at least one protrusions.

6. A pressure relief valve according to claim 4, wherein the at least one protrusion is three or more protrusions.

7. A pressure relief valve according to claim 6, wherein the three or more protrusions are an odd number of protrusions and are arranged so as to avoid opposing pole positions with respect to each other.

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