Patent Application
20230100392
The present application claims priority from Japanese application P2021-160294 filed on Sep. 30, 2021, the content of which is hereby incorporated by reference into this application.
The present disclosure relates to a variable volume device, a sealed tank system using such a variable volume device and a method for manufacturing a bellows.
A fuel such as gasoline in a fuel tank may vaporize due to an environmental temperature or the like, and in order to prevent the vaporized fuel from being discharged to the atmosphere, the vaporized fuel is adsorbed to a canister or the like, is discharged from the canister when an engine or the like is operated and is utilized. There is an upper limit for the amount of fuel adsorbed to the canister, and it is likely that timing at which the adsorbed fuel is able to be utilized is limited. Hence, with consideration given to the environment, a sealed tank system is proposed which prevents the discharge of the vaporized fuel to the outside.
In the sealed tank system as described above, when the vaporization of the fuel proceeds, a pressure in the tank is increased. Hence, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 2013-95338, the pressure resistance of a tank is increased or a mechanism for changing the volume of part which stores a fuel is provided, with the result that variations in pressure are suppressed. As the mechanism for changing the volume, a mechanism using a bellows structure such as a bellows is known.
However, in a normal bellows, when variations in volume are repeated, a bellows portion is repeatedly folded and extended, and stress is especially concentrated on the folded portion, with the result that there is a concern about lack of durability. With consideration given to the useful life of a fuel tank used in a vehicle and the like, it is necessary to realize sufficient durability even when an operation of changing the volume is repeated.
According to one aspect of the present disclosure, a variable volume device (50, 50A) is provided. The variable volume device (50, 50A) comprises: a bellows (60) that includes a bellows structure portion (63) on a tubular member; and a coupling port (62) that couples to an internal space of the tubular member to an internal space of a fuel tank (15). Here, the bellows structure portion (63) includes, in a cross section along a central axis of the tubular member: a first portion (71) which protrudes outward in a radial direction of the tubular member and is formed in an arc shape; a second portion (72) which is recessed inward in the radial direction relative to the first portion (71) and is formed in an arc shape; and a coupling portion (73) which makes the first portion (71) couple to the second portion (72) without any singularity, and the central angle (θ) of each of the arc shapes of the first portion (71) and the second portion (72) is greater than 180 degrees. The variable volume device (50, 50A) is able to realize the bellows (60) capable of increasing the amount of change of the internal volume and having high durability. The variable volume device (50, 50A) is used, and thus it is possible to easily realize a sealed tank system (10, 10A).
According to another aspect of the present disclosure, a method for manufacturing a bellows used for the above-mentioned variable volume device (50, 50A). The method for manufacturing the bellows includes: a step (T100) of molding the tubular member into a shape in a state where the bellows structure portion (63) is extended; a step (T120) of surrounding a predetermined area including a top of a first portion (71) of the bellows structure portion (63) by an outer ring mold (171) including a concave portion whose cross section along the center axis of the tubular member has an arc shape, the first portion (71) protruding outward in a radial direction; a step (T110) of surrounding a predetermined area including a valley of a second portion (72) of the bellows structure portion (63) by an inner ring mold (172) including a convex portion whose cross section along the center axis of the tubular member has an arc shape, the second portion (72) being recessed inward in the radial direction relative to the first portion (71); a step (T140) of bringing the tubular member into a plastically deformable first state and compressing the bellows structure portion (63) in a direction in which the outer ring mold (171) and the inner ring mold (172) are moved close to each other; and a step (T150 to T170) of bringing the tubular member plastically deformed by the compressing into an elastically deformable second state and extending the bellows structure portion (63) to remove the outer ring mold (171) and the inner ring mold (172). In this way, it is possible to easily provide the bellows (60) including the bellows structure portion (63) which is rich in elasticity and has excellent durability.
As shown in the figure, in the fuel tank 15, the fuel supply pipe 16 is provided. The fuel supply pipe 16 is a pipe which introduces the fuel into the fuel tank 15 from a fuel filler opening at its upper end portion, and a tank cap 17 is detachably attached to the fuel filler opening. The interior of the upper end portion of the fuel supply pipe 16 and a gas layer portion in the fuel tank 15 communicate with each other through a breather pipe 18. In the fuel filler opening, a lid 48 capable of being opened and closed to the side of the vehicle is provided, and a lid opener 47 which receives an instruction from the outside to open or close the lid 48 is also provided.
A fuel supply pump device 19 is provided in the fuel tank 15. The fuel supply pump device 19 includes: a fuel pump 20 which sucks the fuel in the fuel tank 15 and pressurizes and discharges the fuel; a sender gauge 21 which senses the liquid surface level of the fuel; a tank internal pressure sensor 22 which detects the inner pressure of the tank as a pressure relative to atmospheric pressure; and the like. The fuel pumped from the fuel tank 15 by the fuel pump 20 is supplied though an unillustrated fuel path to a fuel injection valve provided in an engine.
The evaporated fuel processing device 12 includes a vapor path 31, a purge path 32, a canister 34 and an electromagnetic valve 38. The electromagnetic valve 38 is provided partway through the vapor path 31. One end portion (upstream side end portion) of the vapor path 31 communicates with the gas layer portion in the fuel tank 15. The other end portion (downstream side end portion) of the vapor path 31 communicates with the interior of the canister 34. Activated charcoal (not shown) serving as an adsorbent is filled in the canister 34. The evaporated fuel in the fuel tank 15 is adsorbed to the adsorbent (activated charcoal) in the canister 34 through the vapor path 31. An atmospheric path 43 communicates with the canister 34. The other end portion of the atmospheric path 43 is opened to the atmosphere. The atmospheric path 43 may be omitted.
In the gas layer portion within the fuel tank 15, at the upstream side end portion of the vapor path 31, a full tank detection valve 35 and a fuel cut-off valve 36 are provided. The full tank detection valve 35 is a full tank regulation valve configured with a float valve which is opened and closed by the buoyancy of the fuel, and when the liquid surface of the fuel in the fuel tank 15 is equal to or lower than the liquid surface of the full tank, the float valve is in an opened state whereas when the liquid surface of the fuel is raised to the liquid surface of the full tank by refueling, the float valve is closed to interrupt the vapor path 31. When the vapor path 31 is interrupted, the fuel is filled up to the fuel supply pipe 16, the auto-stop mechanism of a refueling gun is operated and thus the refueling is stopped. The fuel cut-off valve 36 is configured with a float valve which is opened and closed by the buoyancy of the fuel, and is normally held in an opened state, and when the vehicle is rolled over, the fuel cut-off valve 36 is opened to interrupt the flow of the fuel in the fuel tank 15 into the vapor path 31.
The electromagnetic valve 38 provided partway through the vapor path 31 is electrically controlled to open or close the path so as to adjust the flow rate of an evaporated fuel-containing gas (referred to as a “fluid”) flowing through the vapor path 31. In the electromagnetic valve 38, a relief valve may be provided in order to keep appropriate the pressure in the fuel tank 15 when the electromagnetic valve 38 is closed.
The purge path 32 is a path which purges the fuel adsorbed to the canister 34 to the side of the engine when the engine is operated in order to utilize it as the fuel. In the purge path 32, an electromagnetic valve and the like for controlling timing at which the fuel is purged and an unillustrated ECU and the like for controlling the electromagnetic valve and the like are provided. Electrical components such as the electromagnetic valve 38, the lid opener 47 and the fuel pump 20 are also coupled to the ECU as described above, and each of the electrical components receives an instruction from the ECU to operate at desired timing. The detailed description and illustration of the coupling and operations thereof are omitted.
The structure of the variable volume device 50 which is coupled partway through the vapor path 31 extending from the fuel tank 15 to the electromagnetic valve 38 will be described.
Here, the central angle of each of the arc shapes of the first portion 71 and the second portion 72 is greater than 180 degrees. In the present embodiment, the central angles θ each are 270 degrees. The central angles of the first portion 71 and the second portion 72 each are preferably greater than 180 degrees or may be equal to or different from each other as long as the first portion 71 and the second portion 72 are coupled by the coupling portion 73 without any singularity. The length of the coupling portion 73 is shorter than the length of the arc of the first portion 71. The length of the coupling portion 73 is more preferably shorter than half of the length of the arc of the first portion 71. The length of the coupling portion 73 may be zero. The coupling portion 73 may have a linear shape or a curved shape or may include both the shapes. Preferably, with consideration given to the deformation of the bellows structure portion 63 caused by the internal pressure, the shapes of the five first portions 71, the shapes of the four second portions 72 and the shapes of the nine coupling portions 73 are individually the same as each other. If the thicknesses and the materials of the first portions 71 and the second portions 72 are originally adjusted such that the first portions 71 and the second portions 72 are individually deformed in the same manner, the first portions 71 and the second portions 72 do not necessarily need to have the same shapes.
The deformation of the bellows structure portion 63 having the configuration described above will be described. The bellows 60 provided in the variable volume device 50 receives the pressure of the evaporated fuel (hereinafter referred to as the “internal pressure”) through the vapor path 31 to change its length in the direction of the central axis AX, and thereby changes the internal volume. When the length in the direction of the central axis AX is increased, the internal volume is increased whereas when the length in the direction of the central axis AX is decreased, the internal volume is decreased. The deformation of the bellows structure portion 63 caused by the internal pressure will be schematically described with reference to
In
When in this state, the internal pressure exceeds the atmospheric pressure, the bellows structure portion 63 is increased in length along the central axis AX, on the assumption that the outermost point 1p of the first portion 71 is a reference point, as indicated by the broken line BE, the innermost point 1v of the second portion 72 is moved to a point 2v. Here, in the bellows structure portion 63 of the present embodiment, the distance a from the central axis AX to the innermost point 2v of the second portion 72 is substantially equal to the distance a to the innermost point 1v before being moved. This is because the central angle θ of each of the first portion 71 and the second portion 72 is greater than 180 degrees. A distance (line length) from the outermost point 1p of the first portion 71 to the innermost point 1v of the second portion 72 along the bellows structure portion 63 is sufficiently longer than a linear distance from the outermost point 1p to the innermost point 1v. In actuality, as the bellows structure portion 63 is moved along the central axis AX by the internal pressure, the curvature radii of the arc portions of the first portion 71 and the second portion 72 are increased. Consequently, even when the bellows structure portion 63 is extended in the direction of the central axis AX by the internal pressure, a force is almost never exerted which changes the distances from the central axis AX to the outermost point 1p of the first portion 71 and to the innermost point 2v of the second portion 72 in the radial direction. In other words, even when the bellows structure portion 63 is extended by the internal pressure, a large force in the radial direction is not exerted on the first portion 71 and second portion 72. In the bellows structure portion 63, as shown in
As shown in the figure, in the initial state where the internal pressure is not applied, the outermost point 1p of the bellows in the radial direction is separated by a distance b1 from the central axis AX, and the innermost point 1v in the radial direction is separated by a distance a1 from the central axis AX. When the internal pressure is increased in this state, the bellows is extended in the direction of the central axis AX, and however, the outermost point 2p needs to be moved to a position a distance b2 from the central axis AX and the innermost point 2v needs to be moved to a position at a distance a2 from the central axis AX so that the bellows is extended. Consequently, b1>b2 and a1<a2. In other words, in the conventional bellows, deformation in which the outer diameter of the bellows, is decreased and the inner diameter is increased is inevitably caused so that the bellows is extended along the central axis AX.
This is due to the following reasons. Since in the bellows shown as the reference example, the central angles of the arch-shaped portions corresponding to the first portion and the second portion are less than 180 degrees, and the radii of the arcs are small, even when the curvature radii of the portions are increased, the distance from the outermost point 1p to the innermost point 2v is little affected. The straight portion connecting both the portions is inclined as the bellows is extended, and thus a distance perpendicular to the central axis AX in the radial direction is shortened. Hence, a load for deforming the bellows inward in the radial direction is applied to the outermost point, and a load for deforming the bellows outward in the radial direction is applied to the innermost point.
As described above using the reference example, when in the bellows, the amount of movement along the direction of the central axis AX is increased in order to greatly increase or decrease the internal volume, a load for causing deformation in the radial direction is applied to the bellows, in particular, to around the outermost point and to around the innermost point in the radial direction. In the conventional bellows, a load is applied to decrease the diameter of the outer circumference in the radial direction and to increase the diameter of the inner circumference in the radial direction, and moreover, the curvature radii of the outermost circumference and the innermost circumference are small, with the result that stress is repeatedly applied to the portions to make it difficult to acquire sufficient durability. By contrast, in the present embodiment, the problem as described above is unlikely to occur, and thus it is possible to increase and decrease the internal volume, with the result that it is possible to realize high durability. Although in the above description, as the bellows 60, the bellows in the cylindrical shape shown in
In the variable volume device 50 using the bellows 60 of the embodiment described above, the internal volume is able to be significantly increased by the internal pressure, and moreover, high durability is realized. Hence, in the fuel tank system 10 using the variable volume device 50, the fuel tank 15 is sealed, and when the evaporation of the fuel proceeds and thus the internal pressure of the fuel tank 15 is increased, the internal volume of the variable volume device 50 is increased, with the result that the increase in the internal pressure is suppressed. Hence, a description will be given of the operation of the fuel tank system 10 using the sealed fuel tank 15 and the variable volume device 50 of the present embodiment.
The electromagnetic valve 38 is maintained in a closed state except the time of refueling when the fuel is supplied to the vehicle. Hence, the evaporated fuel in the fuel tank 15 is prevented from flowing into and being adsorbed to the canister 34. When in a state where the electromagnetic valve 38 is closed such as a case where the vehicle is parked, the fuel in the fuel tank 15 is evaporated, as described above, the internal volume of the variable volume device 50 is changed, with the result that the internal pressure of the fuel tank 15 is kept in an appropriate range.
Although the electromagnetic valve 38 is also maintained in a closed state while the vehicle is traveling, when predetermined purge conditions are established, for example, an unillustrated electromagnetic valve is opened to make the canister 34 communicate with an unillustrated intake path of the engine through the purge path 32. Consequently, the intake negative pressure of the engine acts on the interior of the canister 34 through the purge path 32, the evaporated fuel adsorbed to the canister 34 is purged to the intake path and is burned in the engine. With respect to the purging of the evaporated fuel, the electromagnetic valve 38 may be opened to purge the evaporated fuel in the fuel tank 15, and thus the internal pressure of the fuel tank 15 may be lowered to about the atmospheric pressure.
When an unillustrated lid switch for opening the lid 48 is operated for refueling, the electromagnetic valve 38 is opened. Here, when the internal pressure of the fuel tank 15 is greater than the atmospheric pressure, the bellows 60 of the variable volume device 50 is expanded. However, at the same time when the electromagnetic valve 38 is opened, the evaporated fuel in the fuel tank 15 and the variable volume device 50 is passed through the vapor path 31 and is adsorbed to the adsorbent in the canister 34. In this way, the internal pressure of the fuel tank 15 is lowered, and thus the lid 48 is opened, and even when the fuel is supplied, the discharge of the evaporated fuel to the atmosphere is prevented or suppressed. A configuration may be adopted in which even when the lid switch for providing an instruction to open or close the lid is operated, the lid 48 is not immediately opened, the adsorption of the evaporated fuel to the canister 34 proceeds, the internal pressure of the fuel tank 15 is lowered to a value near the atmospheric pressure and thereafter the lid 48 is opened. In this way, even when the lid 48 is opened and the tank cap 17 is opened, the discharge of the evaporated fuel to the atmosphere is prevented. This is also true during refueling. Until refueling is completed and the lid 48 is closed, the electromagnetic valve 38 may be maintained in an opened state. In this way, even when the evaporated fuel is generated at the time of refueling, the evaporated fuel is passed through the vapor path 31 and is adsorbed to the adsorbent in the canister 34.
The fuel tank system 10 described above is sealed, uses the variable volume device 50 to increase the volume of the gas phase portion of the fuel tank 15 and is thereby able to prevent the increase in the pressure of the fuel tank 15. Hence, it is not necessary to excessively increase the pressure resistance of the fuel tank 15. Consequently, the thickness of the plate of the fuel tank 15 does not need to be excessively increased, and thus the weight of the fuel tank 15 is prevented from being increased. As a result, this can also contribute to improving the fuel efficiency of the vehicle and the like. Furthermore, it is possible to suppress the necessity for fitting a heat insulator or the like to the fuel tank 15 to reduce an increase in the temperature of the fuel tank 15. It is also unnecessary to provide a complicated mechanism for changing the volume of the fuel tank 15 itself.
Furthermore, in a hybrid car, a plug-in hybrid car or the like where timing at which the fuel adsorbed to the canister 34 is burned in the engine is limited, the volume of the canister 34 does not need to be excessively increased, and an event in which the evaporated fuel incapable of being adsorbed is inevitably discharged to the atmosphere is easily avoided. Moreover, since the bellows 60 of the variable volume device 50 used therefor has high durability, the bellows 60 is able to be used for a long period of time.
A method for manufacturing the bellows 60 serving as the variable volume device described above will be described.
When one layer is formed, examples of the material having permeability resistance include polyamides such as PA11 and PA66 whereas when two layers are formed, examples of the material having permeability resistance include PA12/PA9T, ETFE/PA12, ETFE/PA1012 and the like. Even a resin, such as a PE single layer, which has low fuel permeability resistance in itself may be utilized as long as post-processing or the like is performed to enhance the permeability resistance. Multiple layering including EVOH, PA and ETFE may be originally formed to provide permeability resistance.
The pre-molded product 160 includes a tubular portion 163 which is finally molded into the bellows structure portion 63 and a small diameter portion 162 which is molded into the coupling port 62. The tubular portion 163 is pre-molded into a shape where a convex portion and a concave portion are repeated according to the shapes of the first portions 71 and the second portions 72 of the bellows 60.
An operation of fitting an inner ring mold to the pre-molded product 160 subjected to the pre-molding is then performed (step T110). The inner ring mold 172 is a mold which has a circular cross section and is ring-shaped, and is arranged in a plurality of parts (in this example, four parts) of the pre-molded product 160 that are most recessed in order to mold the second portions 72 in the pre-molded product 160. The inner ring mold 172 is divided into a first ring mold 172a and a second ring mold 172b which have approximately the same shape, and the first ring mold 172a and the second ring mold 172b are fitted to each other to form the inner ring mold 172 surrounding the entire innermost circumference of the pre-molded product 160. This state is shown in the column (A) and the column (B) of
Following the arrangement of the inner ring mold 172, an operation of fitting an outer ring mold 171 is performed (step T120). The outer ring mold 171 is arranged on parts of the pre-molded product 160 which project most outward. The outer ring mold 171 has a cross-sectional shape where its inner side is recessed in an arc shape, and two members are fitted to each other from the outside as in the inner ring mold 172 to surround the entire outermost circumference of the pre-molded product 160. The outer ring mold 171 is arranged on a plurality of parts (in this example, five parts) according to the shape of the pre-molded product 160. This state is shown in the column (C) of
In this way, the inner ring mold 172 is arranged in the innermost circumferential portion of the pre-molded product 160, and the outer ring mold 171 is arranged on the outermost circumferential portion, and thereafter a compression molding device is fitted (step T130). An example of the compression molding device 180 is shown in
In the compression molding device 180, among parts where links are externally combined, the outer ring mold 171 is arranged on parts placed inward relative to the pre-molded product 160. At a link tip of link final ends on the side (outer side) where the outer ring mold 171 is not arranged, a drive pin 181a is provided, and the drive pin 181a is slidably placed in a groove 181b. When in this state, the drive pin 181a is made to slide in the groove 181b, as shown in
Then, the compression molding device 180 is fitted to the pre-molded product 160 (step T130), the pre-molded product 160 is heated and the pre-molded product 160 is compressed using the compression molding device 180 and is thereafter cooled (step T140). The pre-molded product 160 is compressed into a shape shown in
After the molded bellows 60 is sufficiently cooled, the compression molding device 180 is then removed (step T150). Thereafter, air having a predetermined pressure is fed into the bellows 60 from the coupling port 62 to extend the bellows structure portion 63 of the bellows 60 (step T160). This state is illustrated in
An example of the bellows 60 manufactured by the steps described above is shown in the column (A) of
Another embodiment serving as a fuel tank system 10A is shown in
In this way, as in the first embodiment, when the pressure in the fuel tank 15 is increased, the internal volume of the variable volume device 50A is increased, and thus the increase in the internal pressure of the fuel tank 15 is suppressed. Since the variable volume device 50A is arranged in the vertical direction, and thus the coupling port 62 is directed in a vertically downward direction, the fuel to be supplied to the fuel supply pipe 16 is unlikely to enter the variable volume device 50A, and even if the fuel enters the variable volume device 50A, the fuel is returned to the side of the fuel supply pipe 16 by its weight and is discharged. When the variable volume device 50A is arranged along the vertical direction as described above, the direction of compression of the variable volume device 50A coincides with the direction of gravity. Hence, instead of the compression spring 55, a weight having a predetermined weight may be arranged on the blocking wall 61 of the bellows structure portion 63 to assist the compression of the bellows structure portion 63 when the internal pressure of the fuel tank 15 is lowered. The variable volume device 50A may be provided near the fuel supply pipe 16, and for example, in the case of a vehicle, the variable volume device 50A may also be installed in a wheelhouse.
(1) The variable volume device of the present disclosure may be practiced in other embodiments. A variable volume device according to another embodiment includes: a coupling port which is coupled to an internal space of a fuel tank; and a variable volume portion in which the length of a bellows structure portion provided on an outer circumference of a tubular member in an axial direction is extended and compressed by an internal pressure of the fuel tank such that the volume of the tubular member is changed. Here, the bellows structure portion may include: a first portion which protrudes outward in the radial direction of the tubular member and is formed in an arc shape in a cross section along a central axis of the tubular member; a second portion which is recessed inward in the radial direction relative to the first portion and is formed in an arc shape; and a coupling portion which makes the first portion couple to the second portion without any singularity, and the central angle of each of the arc shapes of the first portion and the second portion may be greater than 180 degrees. In this way, when the internal pressure of the fuel tank coupled to the variable volume portion exceeds the atmospheric pressure, the length of the bellows structure portion in the radial direction is increased, the internal volume thereof is increased and the increase in the internal pressure of the fuel tank is suppressed. Here, since in the first portion and the second portion of the bellows structure portion, the central angle thereof is greater than 180 degrees and the bellows structure portion includes the coupling portion which makes the first portion couple to the second portion without any singularity, the length of the bellows structure portion in the axial direction is increased over a predetermined range without the outermost diameter of the first portion and the innermost diameter of the second portion being significantly changed. Hence, the variable volume portion is able to realize high durability without large stress being applied to the portions of the bellows structure portion.
Here, the coupling portion preferably couples the first portion and the second portion without any singularity, and the length thereof may be zero. For example, when the first portion and the second portion are symmetric with respect to an axis line in the radial direction, the central angle of the first portion is α° and the central angle of the second portion is β° and α and β satisfy formula (1) below, since a tangential direction at an end point of the first portion coincides with a tangential direction at an end point of the second portion, both the end points are preferably directly coupled or coupled with the linear coupling portion having a predetermined length.
α=β and 180<α, β≤270 (1)
When both the end points of the first portion and the second portion are directly coupled, the coupling portion is a point and does not have a substantial length. When the coupling portion is originally curved, conditions under which the coupling portion is coupled to the second portion without any singularity are relaxed. For example, α and β may be equal to or greater than 270. In this case, α≠β may be established or the first portion and the second portion do not need to be symmetric with respect to the axis line in the radial direction.
Since the variable volume device is coupled to the internal space of the fuel tank by the coupling port, when the internal pressure of the fuel tank is increased, the internal volume of the variable volume portion of the variable volume device is increased, and thus the increase in the internal pressure of the fuel tank is suppressed. Hence, it is possible to easily configure a sealed tank system.
(2) In the configuration described above, the coupling port may be provided at one end of the tubular member in the axial direction and a blocking wall may be provided at the other end. In this way, the pressure of the fuel tank with the tubular member coupled to the coupling port is directly received by the blocking wall, and thus the movement of the bellows structure portion provided in the tubular member in the axial direction is smooth. An elastic member such as a spring is fitted to the blocking wall, and thus it is easy to support the movement of the bellows structure portion in the direction of compression. The coupling port and the blocking wall may be originally arranged at parts other than both ends in the axial direction. For example, the coupling port may be provided to be directed in a direction intersecting the axial direction of the bellows structure portion.
(3) In the configuration described above, a biasing member which biases the tubular member to the side of an initial position may be fitted to the blocking wall. In this way, the material of the bellows structure portion does not need to be a material which exhibits elasticity for returning to the initial position after deformation caused by the internal pressure. Hence, the flexibility of selection of the material of the bellows structure portion is increased. The material and the structure of the bellows structure portion which exert a force for returning to the side of the initial portion may be originally adopted. As the biasing member, a spring, an elastomer or the like may be used. A compression spring which biases the blocking wall from the outside may be adopted or a tension spring which is provided inside the bellows structure portion to bias the blocking wall to inward may be adopted. The spring may be a coil spring or a plate spring. When the bellows structure portion is arranged in the vertical direction with the blocking wall on the upper side, the biasing member may be a heavyweight material which biases the blocking wall downward by gravity, that is, to the side of the initial position. A configuration may be adopted in which the blocking wall is biased by magnetic force, compressed air or the like.
(4) In the configuration described above, the tubular member may be formed in a cylindrical shape. In this way, there is no part where stress is easily concentrated in the circumferential direction of the tubular member, and thus it is possible to enhance the durability of the bellows structure portion. The tubular member may be a rectangular tubular shape or the like, and has preferably a shape in which the installation space of the variable volume device is able to be effectively utilized.
(5) In the configuration described above, two or more first portions and two or more second portions may be provided. In this way, it is possible to increase the internal volume of the variable volume portion. The number of first portions may be equal to the number of second portions, or the first portions may be provided one more than the second portions.
(6) In a sealed tank system including: a fuel tank; a canister which is coupled to the fuel tank by a pipe path to adsorb an evaporated fuel; an on-off valve which is provided in the pipe path; and any one of the variable volume devices described above, the coupling port of the variable volume device may be configured to be coupled to the pipe path. In this way, it is possible to easily configure the sealed tank system, and the volume of the variable volume portion of the variable volume device is changed to be able to easily suppress the increase in the pressure in the fuel tank. In this case, the on-off valve may be an electric valve such as an electromagnetic valve, and may be opened and closed according to the operation conditions of a vehicle or the like to control timing at which the evaporated fuel in the fuel tank is guided to the canister. In order to control the timing as described above, a control unit such as an ECU may be provided.
(7) Alternatively, in a sealed tank system including: a fuel tank; a fuel supply pipe which couples the fuel tank and a fuel filler opening; and any one of the variable volume devices described above, the coupling port of the variable volume device may be configured to be coupled to the fuel supply pipe. In this way, it is also possible to easily configure the sealed tank system, and the volume of the variable volume portion of the variable volume device is changed to be able to easily suppress the increase in the pressure in the fuel tank.
Even when any one of the configurations described above is adopted, since the durability of the variable volume device is high, it is possible to reduce the maintenance of the sealed tank system. It is not necessary to excessively increase the pressure resistance of the fuel tank in order to achieve a sealed tank system. Furthermore, since it is possible to suppress the adsorption of the evaporated fuel to the canister, even when timing at which the fuel adsorbed to the canister is burned is limited, the adsorbent of the canister does not need to be excessive.
(8) In the configuration described above, the variable volume device may be arranged such that the coupling port is directed in a vertically downward direction. In this way, even when the fuel being supplied enters the variable volume device, the fuel is able to be easily discharged by its weight.
(9) In another embodiment of the present disclosure, a method for manufacturing a bellows used for the above-mentioned variable volume device. The manufacturing method includes: molding the tubular member into a shape in a state where the bellows structure portion is extended; surrounding a predetermined area including a top of a first portion of the bellows structure portion by an outer ring mold including a concave portion whose cross section along the center axis of the tubular member has an arc shape, the first portion protruding outward in a radial direction; surrounding a predetermined area including a valley of a second portion of the bellows structure portion by an inner ring mold including a convex portion whose cross section along the center axis of the tubular member has an arc shape, the second portion being recessed inward in the radial direction relative to the first portion; bringing the tubular member into a plastically deformable first state and compressing the bellows structure portion in a direction in which the outer ring mold and the inner ring mold are moved close to each other; and bringing the tubular member plastically deformed by the compressing into an elastically deformable second state and extending the bellows structure portion to remove the outer ring mold and the inner ring mold. In this way, it is possible to easily provide the bellows including the bellows structure portion which is rich in elasticity and has excellent durability.
Here, as long as the tubular member is made of a material such as a synthetic resin which is able to be brought into the plastically deformable first state and is also able to be brought into the elastically deformable second state, the material is able to be adopted. For example, it is possible to use a synthetic resin or the like which has thermoplasticity or photoplasticity. When one layer is formed, examples of the synthetic resin having thermoplasticity include polyamides such as PA11 and PA66 whereas when two layers are formed, examples of the synthetic resin having thermoplasticity include PA12/PA9T, ETFE/PA12, ETFE/PA1012 and the like. Ad-PE/EVOH/Ad-PE/PE of four layers and the like may be utilized. In addition, a multilayer structure of nylon or fluorine and EVOH (ethylene-vinyl alcohol copolymer) may also be adopted. Since the tubular member is highly likely to make contact with the evaporated fuel from the fuel tank, the tubular member preferably has permeability resistance to the fuel. Even a resin, such as a PE single layer, which has low fuel permeability resistance in itself may be utilized as long as a low-permeability and a multilayer structure are provided or a low-permeability covering or coating is formed by post-processing to enhance the permeability resistance. Instead of the synthetic resin, an elastic material such as rubber may be used.
The outer ring mold and the inner ring mold preferably have shapes corresponding to the outer shape of the tubular member, and when the tubular member has a cylindrical shape, they preferably have shapes in which the inner side is circular. When a cross section of the tubular member perpendicular to the axial direction is rectangular, the ring members preferably have shapes in which the inner side is rectangular.
(10) In the configuration described above, the outer ring mold and the inner ring mold each may be divided into a plurality of parts in a circumferential direction. In this way, firstly, the inner ring mold is able to be easily fit to the extended tubular member, and is able to be easily removed after the compression. The number of divisions is preferably two or more, and the outer ring mold and the inner ring mold may be divided in the same positions or may be divided in different positions.
(11) In the configuration described above, the tubular member may be formed of a thermoplastic synthetic resin, the first state may be a state where the temperature of the synthetic resin is kept equal to or greater than a temperature at which the synthetic resin is plastic and the second state may be a state where the temperature of the synthetic resin is kept less than the temperature at which the synthetic resin is plastic. In this way, it is possible to easily compress the tubular member and to easily elastically deform the bellows structure portion in the manufactured bellows by the internal pressure.
(12) The present disclosure is not limited to the embodiments described above and may be realized by various configurations without departing from the spirit thereof. For example, the technical features of the embodiments corresponding to the technical features in the aspects described in SUMMARY may be replaced or combined as necessary so that part or the whole of the problems described above are so1v ed or part or the whole of the effects described above are achieved. When the technical features are not described as essential features in the present specification, they may be deleted as necessary. For example, part of the configuration realized by hardware in the embodiments may be realized by software.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-160294 | Sep 2021 | JP | national |
