JP2009056897A - Float for dme fuel tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a float for a DME fuel tank arranged in a fuel tank for storing DME fuel and capable of being accurately and stably floated following a liquid surface height of the DME fuel. <P>SOLUTION: The float for the DME fuel tank comprises a hollow body molded of PPS resin or a synthetic resin material containing the PPS resin a main component, having specific gravity of 0.5 or smaller and a pressure-resistance strength of 1.8 MPa or higher and including an air tight cavity 18. Thereby, the float has an excellent barrier property that the DME fuel is not totally intruded, is floated on the liquid surface of the DME fuel, and can sufficiently withstand the internal pressure of the fuel tank 1. The float 10 for the DME fuel tank can be accurately and stably floated on the liquid surface of the DME fuel for a long period of time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a float for a DME fuel tank that floats according to the liquid level of the DME fuel provided in a liquid level display device and / or an overfill prevention device provided in a fuel tank that stores DME (dimethyl ether) as fuel. About.

  For example, vehicles such as automobiles tend to increase the number of vehicles using liquefied gas fuel for the purpose of low pollution in accordance with the recent tightening of exhaust gas regulations. As the liquefied gas fuel, liquefied petroleum gas (hereinafter referred to as LPG) fuel is mainstream, but dimethyl ether (hereinafter referred to as DME) fuel is also attracting attention. This DME fuel has an excellent advantage that it has a high cetane number, and can significantly reduce the emission amount of PM and NOx, and is also highly expected as a low pollution measure. For example, Patent Document 1 has been proposed as a fuel tank for storing DME fuel.

  By the way, in the fuel tank for storing the above-mentioned LPG fuel, generally, a liquid level display device for confirming the storage amount of the LPG fuel or the maximum filling when the LPG fuel is filled in the fuel tank. An overfill prevention device is installed to prevent overfilling. Here, as the liquid level display device, for example, as in Patent Document 2, a float that floats according to the liquid level height of the LPG fuel stored in the fuel tank is provided, and the amount of LPG fuel stored (depending on the height position of the float) A liquid level (height) is measured and displayed. In the liquid level display device having such a configuration, the arm connected to the float rotates according to the float floating, and displays the storage amount (or liquid level height) according to the rotation position (angular position). It has become.

  On the other hand, as an overfill prevention device, for example, as in Patent Document 3, a float that floats according to the liquid level of the LPG fuel stored in the fuel tank is provided, and the float is a liquid that is the maximum filling amount of the fuel tank. There has been proposed a system in which the filling of the LPG fuel is forcibly stopped when the surface height position is reached. In the overfill prevention device having such a configuration, the inlet for flowing LPG fuel into the fuel tank, the opening / closing valve for opening / closing the inlet, the arm connected to the float, and the opening / closing valve by tilting the arm are provided. And a cam mechanism for opening and closing. Here, the on-off valve is urged in a direction to close the inlet, and when the liquid level is lower than the maximum filling amount, the on-off valve is caused to flow against the urging force by the cam mechanism. The entrance is open. Then, when filling the LPG fuel, when the liquid level height reaches the maximum filling amount, the cam mechanism is actuated by the float at the liquid level position, and the on-off valve is moved into the inlet according to the urging force. Is the closing position. As described above, when the LPG fuel is filled, the overfill prevention device forcibly closes the inlet when the maximum filling amount is reached so that no further filling is performed.

JP 2001-115898 A JP 2001-201390 A JP 2007-155046 A

  In the case where the above-described DME is used as the fuel, since this DME fuel is a high-pressure gas similar to the LPG fuel, it is possible to utilize equipment for the LPG fuel. Here, in the above-described liquid level display device and overfill prevention device arranged in the fuel tank for LPG fuel, the float is generally formed of low density and high strength foam rubber. Is used. Furthermore, nitrile rubber is used as the foamed rubber.

  However, when DME fuel is stored in a fuel tank for LPG fuel in which a liquid level display device having a float made of foamed nitrile rubber or an overfill prevention device is arranged, the liquid level display is displayed as the storage period elapses. The stored amount (liquid level height) displayed on the device and the operation of the overfill prevention device become unstable. Specifically, the storage amount displayed by the liquid level display device becomes smaller than the actual storage amount, or the overfill prevention device operates with a filling amount smaller than the prescribed maximum filling amount. Furthermore, the display on the liquid level display device may not move, and the overfill prevention device may not operate. When the DME fuel is stored in the fuel tank for LPG fuel in this way, there arises a problem that the liquid level of the DME fuel stored in the fuel tank cannot be accurately measured as the storage period elapses. This is thought to be because the above-mentioned float made of foamed nitrile rubber cannot float stably according to the liquid level of the DME fuel.

  The present invention is a float disposed in a liquid level display device or an overfill prevention device, and even if DME fuel is stored in a fuel tank, the liquid level display device and the overfill prevention device are not affected by the liquid level height of the DME fuel. A float for a DME fuel tank that can float appropriately according to the liquid level of the DME fuel is proposed.

  The present invention relates to a float for a DME fuel tank, which is disposed in a liquid level display device and / or an overfill prevention device provided in a fuel tank for storing DME fuel and floats according to the liquid level of the DME fuel. Or it consists of a hollow body which is molded from a synthetic resin material containing this as a main component and has an airtight void, and has a specific gravity of 0.5 or less and a pressure strength of 1.8 MPa or more. Is a float for a DME fuel tank. In the present invention, DME is dimethyl ether, and PPS is polyphenylene sulfide.

Here, as a float disposed in a liquid level display device or an overfill prevention device, the compatibility of DME fuel with respect to a float made of foamed nitrile rubber used in a fuel tank for LPG (liquefied petroleum gas) fuel Explain the results of the study.
As a result of storing the DME fuel in the fuel tank equipped with the float made of foamed nitrile rubber and examining the change of the float, the weight and volume of the float are larger than the storage period of the DME fuel. It was confirmed that it increased with progress. This is because the DME fuel enters the inside of the foamed nitrile rubber float. More specifically, the float made of foamed nitrile rubber has a structure having a large number of bubbles, whereas DME fuel has a property that its molecular weight is smaller than that of LPG fuel and it is easy to rotate flexibly by an ether bond. ing. Since a predetermined internal pressure is constantly applied to the fuel tank, a pressure difference occurs between the inside and outside of the float. Due to this pressure difference, the DME fuel is condensed and permeated from the float surface to the inside of the float. Spread with. As a result, it is considered that the DME fuel enters and accumulates in a large number of bubbles inside the float. As described above, in the float made of foamed nitrile rubber, as the storage period of the DME fuel becomes longer, the weight increase and the volume increase due to the penetration of the DME fuel proceed. And since the specific gravity of the float increases, the float position of the float with respect to the liquid surface becomes unstable, or remains floating without floating on the liquid surface, and the liquid level display device and overfill prevention device However, it becomes impossible to measure the liquid level height accurately.

  As a result of examining the above-mentioned foamed nitrile rubber float in more detail, it was found that the bubbles contained in the float were small in the surface layer portion and large in the interior. And, as a form of this float, since it is connected to each device main body of the liquid level display device and the overfilling prevention device through a hook-shaped arm, a through hole for connecting the arm is provided in the float central portion. The configuration is common. In the float made of foamed nitrile rubber having such a structure, the DME fuel that has entered the through-hole relatively easily invades comparatively large bubbles present on the peripheral surface of the hole, and the above-described problems are likely to occur. ing.

  Thus, it is apparent that the foam level made of foamed nitrile rubber used in the fuel tank for storing the LPG fuel cannot measure the liquid level accurately and stably when the DME fuel is stored. Based on the results of this study, the inventors of the present invention conducted a study on a float that floats stably on the liquid surface even when DME fuel was stored, and as a result of earnest study, the DME fuel tank according to the present invention was obtained. Led to the invention of the float.

  The present invention is formed from a PPS resin or a synthetic resin material containing the PPS resin as a main component. Here, the PPS resin has an excellent barrier property that hardly permeates the DME fuel, and also has a property that the density is relatively small and the strength is relatively high. A hollow body enclosing a hermetic air gap with a PPS resin or a synthetic resin material containing the same as a main component so that the specific gravity of the float is smaller than the density of the DME fuel and has sufficient strength to withstand the internal pressure of the fuel tank The DME fuel tank float is configured by the hollow body.

This hollow body is formed of the above PPS resin or synthetic resin and has a structure having an airtight void, so that the specific gravity is 0.5 or less, so the density of DME fuel (0.67 g / cm ³ ) Smaller and can float according to the DME fuel level. Since the PPS resin has an excellent barrier property with respect to the DME fuel as described above, the DME fuel does not permeate, and the DME fuel does not enter the airtight space of the hollow body. From the above, the float for a DME fuel tank of the present invention comprising this hollow body does not increase in mass or volume even when used in a fuel tank for storing DME fuel, and can stably be used for a long time. Can float on the surface.

  Here, when the specific gravity is larger than 0.5, there is a concern that the liquid surface cannot be stably floated. This is because the DME fuel tank float is a member that constitutes a liquid level display device and an overfill prevention device, and is connected to each device body via an arm or the like. This is because the total weight applied to the float increases and the DME fuel cannot float on the liquid level.

  On the other hand, since the hollow body has a pressure strength of 1.8 MPa or more, the float for a DME fuel tank of the present invention comprising the hollow body can sufficiently withstand the internal pressure of the fuel tank storing the DME fuel. Can do. Here, since the DME fuel is a high-pressure gas as described above, a predetermined internal pressure is applied in the fuel tank in order to maintain the liquefied state in the fuel tank. The pressure strength is set so that it can sufficiently withstand the internal pressure of the fuel tank.

  As described above, the DME fuel tank float according to the present invention has a high pressure resistance and an excellent barrier property against DME fuel. Therefore, the DME fuel tank float in the fuel tank storing DME fuel for a long period of time. Therefore, it has excellent durability that it can float stably at the liquid level of DME fuel.

  In addition, as a specific gravity of a hollow body, the structure made into 0.2 or more is preferable. When the specific gravity is smaller than 0.2, it becomes considerably smaller than the density of the DME fuel, so that it floats in response to the fluctuation of the liquid level. Therefore, when the liquid level is shaking, the accurate liquid level height position cannot be measured accurately until the shaking is almost completely stopped, resulting in a time loss. As the specific gravity of the hollow body, a configuration of 0.3 or more and 0.4 or less can be preferably used. As a result, the DME fuel can float more stably at the liquid level, and the time loss can be suppressed as much as possible.

  In addition, as the synthetic resin material having the PPS resin as a main component in this configuration, a material containing a reinforcing material such as glass fiber or an inorganic filler is preferable. And as such a reinforcing material, you may make it contain a single type of thing and may make it contain a multiple types of thing.

In the DME fuel tank float described above, the PPS resin or a synthetic resin material mainly composed of the PPS resin has a density of 1.35 to 1.75 g / cm ³ and a tensile yield strength of 90 MPa or more. A configuration is proposed.

  By forming a hollow body having an airtight void with a PPS resin or a synthetic resin material having such a configuration, the hollow body can be obtained relatively easily as a material that exhibits the above-described specific gravity and pressure strength. be able to. And the float for DME fuel tanks which consists of this hollow body can demonstrate the effect mentioned above appropriately.

Here, the lower limit of the density of the PPS resin is 1.35 g / cm ³ , and the density tends to increase by containing another reinforcing material. And when it becomes larger than 1.75 g / cm ^{3, since} it is necessary to reduce the thickness of the hollow body, the pressure strength tends to decrease, and the specific gravity of the hollow body is 0.5 or less. It is difficult. For this reason, the density of the PPS resin or the synthetic resin material is set. Moreover, by setting the tensile yield strength to 90 MPa or more, it becomes relatively easy to set the pressure resistance of the hollow body to 1.8 Pa or more. When the pressure is less than 90 MPa, it is necessary to increase the thickness of the hollow body, and thus the specific gravity tends to increase, and the pressure strength is difficult to be 1.8 MPa or more. Here, the upper limit value of the tensile yield strength is preferably 210 MPa or less. This upper limit value is set in consideration of efficiency of the manufacturing process and reduction of material costs.

  As the DME fuel tank float described above, the hollow body constituting the float has a hollow cylindrical shape having a cylindrical outer shell body portion, and has a through-hole penetrating along the central axis of the cylinder. A configuration is proposed that includes a central cylindrical portion to be formed and a plurality of rib portions extending from the outer surface of the central cylindrical portion along the radial direction to the inner surface of the outer shell body portion.

  Here, the shape of the hollow body is preferably a spherical shape that can obtain the strength most efficiently, but in order to secure the specific gravity of the present invention in the spherical shape, it is necessary to have a relatively large diameter. By the way, in the manufacturing process of the fuel tank, the hollow body constituting the float of the liquid level display device and the overfill prevention device is formed in the tank through the opening of the mounting seat provided for mounting each of these devices on the tank. I try to put it in. Therefore, the shape of the hollow body needs to be a size that can pass through the opening of the mounting seat. However, the relatively large-diameter spherical hollow body cannot pass through the opening of the mounting seat. Therefore, the hollow body needs to have an outer dimension that can pass through the opening of the mounting seat and has the specific gravity (buoyancy) of the present invention. It is a hollow cylinder set to a length that does not interfere with.

  Since the hollow body having such a configuration is a hollow cylinder having a central cylinder part and an outer shell body part, an airtight space is provided between the central cylinder part and the outer shell body part. Forming part. Thereby, this structure shall have the specific gravity concerning the above-mentioned this invention, and also by having a some rib part, the proof strength with respect to external pressure will improve, and it will have sufficient pressure resistance strength of this invention. Yes. In particular, by providing the rib portion, the thickness of the hollow body can be reduced, so that the specific gravity according to the present invention is easily achieved. Moreover, the through hole for inserting and connecting the arm connected with each apparatus main body of a liquid level display apparatus and an overfilling prevention apparatus is formed by the center cylinder part. By connecting the arm to the through hole, the hollow body of this configuration forms a float. Then, when the float floats according to the liquid level, the arm linked to the float moves up and down, and the liquid level height position at which the float floats through the vertical movement of the arm is indicated by a liquid level display device or Each device body of the overfilling prevention device can be grasped stably.

  The plurality of rib portions are provided in the longitudinal direction of the hollow cylinder so that the ribs divide the hollow body into a plurality of internal airspaces, and each compartment airspace forms an airtight airspace. May be. Thus, by providing a rib part over a longitudinal direction, the compressive strength of a hollow body can be raised further.

  In addition, such a hollow cylindrical hollow body includes a cylindrical outer shell body portion and shielding portions that shield both ends thereof, and two detent projections projecting outwardly on one side shielding portion. The structure which arranges a part in parallel is proposed.

  As described above, the liquid level display device and the overfill prevention device connect the hollow bodies so that the arms connected to the respective device bodies pass through the through holes of the hollow bodies. In this configuration, the arm can be disposed between the rotation-preventing protrusions provided on the shielding portion of the hollow body, thereby preventing the hollow body from rotating with respect to the arm. is doing. Here, if the hollow body is capable of rotating with respect to the arm, the hollow body rotates to cause friction and wear with the arm, thereby reducing the durability of the hollow body. Is concerned. On the other hand, in this configuration, by arranging and connecting an arm between the rotation-preventing protrusions, the hollow body is prevented from rotating, so that wear with the arm can be suppressed and desired. It can be possible to exhibit the durability of.

  In the DME fuel tank float described above, the hollow body constituting the float includes a bottomed outer shell cylinder having an opening at one end, and a lid that shields the opening of the bottomed outer shell cylinder. The structure which joins these is proposed.

  In such a configuration, a hollow cylindrical hollow body is formed by joining a bottomed outer shell cylinder and a lid, and it is relatively easy to have a form including an airtight void. It can be molded into. And since a bottomed outer shell cylinder and a lid are each formed, the thickness of each plate can be easily reduced, and a configuration satisfying the specific gravity of the present invention can be obtained relatively easily. Further, it is easy to integrally mold the above-described center cylinder part and rib part into the bottomed outer shell cylinder. For example, a relatively complicated shape can be easily and stably formed by injection molding of PPS resin or synthetic resin material. Can be molded. In addition, various methods such as ultrasonic bonding, heat fusion, induction heat fusion, etc. can be used as a joining method for joining the bottomed outer shell and the lid, but in consideration of manufacturing efficiency. Then, ultrasonic bonding can be used suitably.

  In addition, the hollow body formed from the bottomed outer shell cylinder and the lid has a configuration including a cylindrical outer shell body and shielding portions that shield both ends of the outer shell body. That is, the bottomed outer shell cylindrical body has a configuration in which an outer shell body and a shielding portion that shields one end of the outer shell body are integrally provided, and the lid body is provided at the other end of the outer shell body. The shielding part which shields an opening part is comprised.

  The above-described bottomed outer shell cylindrical body includes a plurality of projecting portions projecting inwardly from the inner surface of the outer shell body portion between the rib portions, and the projecting portion is an end on the opening side. A configuration is proposed in which an escape portion that does not contact the lid is formed in the portion.

  In such a structure, the strength and rigidity of the hollow body formed from the bottomed outer shell cylindrical body are improved by providing a plurality of projecting portions on the outer shell body constituting the bottomed outer shell cylindrical body. can do. Therefore, the plate thickness of the hollow body can be further reduced, and the specific gravity can be reduced. Furthermore, the protrusion has a configuration having an escape portion that does not come into contact with the lid at the end on the opening side. This is because stress concentration is likely to occur at the contact portion when the projecting portion comes into contact with the lid body in a state where the lid body is joined to the bottomed outer shell cylinder. Therefore, by providing a relief portion in the protruding portion, stress concentration is prevented, and the effect of improving strength and rigidity can be sufficiently exhibited by the protruding portion.

  The present invention molds a hollow body enclosing a hermetic void with a PPS resin or a synthetic resin material containing the PPS resin so that the specific gravity is 0.5 or less and the pressure strength is 1.8 MPa or more. And a DME fuel tank float constituted by the hollow body. Since the PPS resin has an excellent barrier property that hardly permeates the DME fuel, the hollow body of this configuration hardly causes an increase in weight or volume due to the penetration of the DME fuel. And it has a specific gravity lower than the density of the DME fuel and has a pressure strength sufficient to withstand the internal pressure of the fuel tank. Therefore, the DME fuel tank float made of the hollow body can float on the liquid surface of the DME fuel accurately and stably over a long period in the fuel tank storing the DME fuel. It is installed in the overfill prevention device and the liquid level height is measured accurately and stably, and each device operates properly.

Further, in the configuration in which the PPS resin or the synthetic resin material containing the PPS resin as a main component has a density of 1.35 to 1.75 g / cm ³ and a tensile yield strength of 90 MPa or more, A hollow body having the above-described specific gravity and pressure strength of the present invention can be obtained relatively easily, and the above-described operational effects of the present invention can be appropriately exhibited.

  Further, the hollow body has a hollow cylindrical shape having a cylindrical outer shell body portion, and includes a central cylindrical portion that forms a through-hole penetrating along the cylindrical central axis, and the central cylindrical portion. In the case of a configuration including a plurality of rib portions extending along the radial direction from the outer surface and reaching the inner surface of the outer shell body portion, the above-described specific gravity of the present invention is sufficiently obtained by forming the hollow cylindrical shape. In addition to being satisfactory, the fuel tank can be relatively disposed in the tank by passing through the hole of the mounting seat for mounting each device in the manufacturing process of the fuel tank. Moreover, the pressure resistance strength of the present invention can be sufficiently satisfied by providing a plurality of rib portions. Moreover, since it can be provided so as to be connected to each device main body of the liquid level display device and the overfilling prevention device via an arm connected to the through hole of the central cylindrical portion, each device is provided by a float made of the hollow body. The main body can measure the liquid level height accurately and stably, and each operation can be appropriately performed.

  Here, the hollow body is provided with a cylindrical outer shell body portion and shielding portions that shield both ends thereof, and two anti-rotation projecting portions protruding outward are arranged in parallel on one shielding portion. In such a case, by arranging the arm connected to the above-described apparatus main body between the rotation-preventing protrusions, it is possible to prevent the hollow body from rotating with respect to the arm. And the hollow body can be suppressed, and the float made of the hollow body can exhibit desired strength and rigidity.

  Further, in the case where the above-described hollow body is configured by joining a bottomed outer shell cylinder having an opening at one end and a lid that shields the opening of the bottomed outer shell cylinder. Can form the hollow cylindrical hollow body described above relatively easily. And the float which consists of the said hollow body will show | play suitably the effect of this invention mentioned above.

  Here, the bottomed outer shell cylindrical body is provided with a plurality of projecting portions projecting inward from the inner surface of the outer shell body portion between the rib portions, and the projecting portions are end portions on the opening side. In addition, in the case of the configuration formed by forming a relief portion that does not contact the lid, the strength and rigidity of the hollow body can be improved by this projection, and the relief portion of the projection It is possible to prevent stress concentration caused by the contact between the protrusion and the lid. Thereby, the improvement effect of the intensity | strength and rigidity by a protrusion part can fully be exhibited.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, the result of the immersion test will be described as a preliminary test for studying the material for molding the DME fuel tank float according to the present invention.
As described above, as a float disposed in a liquid level display device or an overfill prevention device provided in a fuel tank that stores LPG (liquefied petroleum gas) fuel, a molded foam rubber (foamed nitrile rubber) is used. Commonly used. This is because foam rubber has a relatively low density and a relatively high tensile yield strength, so that the float molded from the foam rubber has a desired specific gravity lower than the density of the LPG fuel and LPG It can be molded as having a pressure strength that can sufficiently withstand the internal pressure of the fuel tank that stores the fuel. However, the foam rubber applied in the LPG fuel tank penetrates the DME fuel. Therefore, in the float made of foam rubber, the DME fuel penetrates into the inside and increases in weight and volume. The floating of the liquid level becomes unstable, and the height of the liquid level cannot be measured accurately. Therefore, the foamed rubber float used in the LPG fuel tank cannot be used for the fuel tank for storing the DME fuel.

Polytetrafluoroethylene (PTFE) resin and nylon 11 (PA11) resin were examined as materials that hardly penetrate DME fuel. Here, the polytetrafluoroethylene resin has a higher performance (hereinafter referred to as barrier property) that does not permeate the DME fuel than the nylon 11 resin, but the density is relatively high at 2.17 g / cm ^3. It may be difficult to form a float with a lower specific gravity. Therefore, as a result of examining other materials, a PPS resin was found. An immersion test was conducted in which each test piece of PPS resin and nylon 11 resin was immersed in DME fuel.

In this immersion test, rectangular test pieces were respectively formed from PPS resin and nylon 11 resin, and each test piece was immersed in DME fuel, and the respective weight changes after 72 hours and 168 hours were measured. . The results are shown in Table 1 below. As a result of this immersion test, the increase in weight after 168 hours was 0.007 g for the PPS resin and 0.087 g for the nylon 11. Accordingly, it was found that the PPS resin has an extremely small increase in weight as compared with the nylon 11 resin before being immersed in the DME fuel, and has a high barrier property against the DME fuel. The density of the PPS resin is 1.35 g / cm ³ , and a float having a specific gravity lower than that of the DME fuel can be molded. From the result of such immersion test, PPS resin or a synthetic resin mainly composed of PPS resin was determined as a material for forming a float used in a fuel tank for storing DME fuel.

Next, the fuel tank 1 for storing DME fuel will be described.
The fuel tank 1 is disposed horizontally on a truck, for example, and as shown in FIG. 1, a cylindrical barrel portion 1a and a hemispherical mirror portion 1b joined to both side openings of the barrel portion 1a. , 1b. The fuel tank 1 is fixed to a vehicle by a fixing member (not shown), and a valve device including a filling valve 45 and a filling valve opening / closing handle 41 for opening and closing the filling valve 45 in one mirror portion 1b. 40 is disposed. The filling valve 45 is provided with a supply port 46 to which DME fuel is supplied from the outside. When filling with DME fuel, fuel is charged from the supply port 46.

  A gas filling pipe 42 communicating with the above-described filling valve 45 is disposed in the fuel tank 1. The tip of the gas filling pipe 42 is arranged at the upper part in the fuel tank 1, and the overfilling prevention device 2 is connected to the tip. As this overfill prevention device 2, a mechanical type is shown in FIG. Here, FIG. 2A shows a filling state in which the overfilling prevention device 2 is allowed to flow in fuel, and FIG. 2B is a filling completion state in which the overfilling prevention device 2 is incapable of flowing in fuel. Is shown. The mechanical overfill prevention device 2 includes a communication passage 53 that allows the gas filling pipe 42 and the inside of the fuel tank 1 to communicate with each other, and an overfill prevention valve 51 that opens and closes an inlet 52 provided in the communication passage 53. It has. The overfill prevention valve 51 is urged and arranged in a direction to close the inflow port 52. The overfill prevention valve 51 is opened (see FIG. 2A) and closed (see FIG. 2). A cam member 54 that converts to B) is provided so as to be rotatable. A cam-shaped arm 55 is connected to the cam member 54, and the cam member 54 is rotated by tilting the arm 55 in the vertical direction, so that the overfill prevention valve 51 is moved to the open position and the closed position. Convert. The DME fuel tank float 10 according to the present invention is connected to the tip of the arm 55. The DME fuel tank float 10 floats according to the liquid level of the DME fuel stored in the fuel tank 1. That is, when the DME fuel in the fuel tank 1 increases or decreases due to consumption or filling, and the DME fuel tank float 10 moves up and down according to the liquid level, the arm 55 tilts up and down and the cam member 54 rotates. The overfilling prevention valve 51 is operated by this rotation. Specifically, when the DME fuel stored in the fuel tank 1 is less than the maximum filling amount that can be stored in the fuel tank 1, as shown in FIG. The float 10 floats and the overfilling prevention valve 51 is held in the open position against the urging force by the cam member 54. When the overfill prevention valve 51 is held at the open position, the inflow port 52 is open, and DME fuel can flow into the fuel tank 1 from the inflow port 52. When the DME fuel is filled, the DME fuel tank float 10 moves up as the liquid level rises, and when the DME fuel reaches the maximum filling amount, as shown in FIG. Further, the DME fuel tank float 10 reaches the liquid level indicating the maximum filling amount. Accordingly, the overfilling prevention valve 51 is converted to the closed position by the cam member 54 in accordance with the biasing force. Thus, when the DME fuel stored in the fuel tank 1 reaches a liquid level that indicates the maximum filling amount, the overfill prevention device 2 closes the inlet 52 and forcibly stops filling the DME fuel, The DME fuel is prevented from flowing in exceeding the maximum filling amount.

  The mechanical overfill prevention device 2 includes an apparatus main body 50 including an overfill prevention valve 51, a cam member 54, an inlet 52, and the like, the arm 55, and the DME fuel tank float 10. Has been. Here, in the apparatus main body 50 and the arm 55, the thing of the same structure as the structure provided in the fuel tank which stores LPG fuel can be used, and it abbreviate | omits about the detail. The DME fuel tank float 10 is the main part of the present invention, and details will be described later.

  On the other hand, a liquid level display device 3 is disposed on the body 1a of the fuel tank 1 (see FIG. 1). As the liquid level display device 3, an instrument part 61 that displays the liquid level height is fixed to the body part 1 a, and a support pipe 62 extends from the instrument part 61 into the fuel tank 1. An operating rod (not shown) is provided in the support tube 62 so as to be capable of rotating about its center axis. Further, a hook-like arm 65 is pivotally supported at the tip of the support tube 62 so as to be pivotable in the vertical direction, and the arm 65 and the operating rod are linked via a gear mechanism (not shown). ing. Thereby, the operating rod rotates as the arm 65 rotates in the vertical direction. The DME fuel tank float 10 according to the present invention is connected to the tip of the arm 65. The DME fuel tank float 10 floats according to the liquid level of the DME fuel stored in the fuel tank 1, and the arm 65 rotates in the vertical direction as the float 10 floats. That is, the arm 65 rotates in the vertical direction according to the liquid level height of the DME fuel, and the operating rod rotates due to the rotation. Therefore, the instrument section 61 according to the rotation position (or rotation angle) of the operating rod. Then, the storage amount (liquid level height) of DME fuel is displayed.

  The liquid level display device 3 includes a device main body 60 including an instrument 61, a support tube 62, an operating rod (not shown), a gear mechanism (not shown), the arm 65, and the DME fuel tank. And float 10. Here, in the apparatus main body 60 and the arm 65, the thing of the same structure as the structure used for the fuel tank which stores LPG fuel can be used, and it abbreviate | omits about the detail. The DME fuel tank float 10 is the main part of the present invention, and details will be described later.

  The fuel tank 1 for storing DME fuel can be of the same configuration as the fuel tank for storing LPG fuel because the DME fuel is a high-pressure gas similar to LPG fuel. Further, as a system for supplying fuel, such as a configuration for sending DME fuel from the fuel tank 1 to the engine, one having the same configuration as the LPG fuel can be used. Details of each configuration and supply system of such a fuel tank are omitted.

  Next, the DME fuel tank float 10 provided in the overfill prevention device 2 and the liquid level display device 3 described above will be described. The DME fuel tank float 10 includes a hollow cylindrical hollow body 12. That is, the hollow body 12 is connected to the arms 55 and 65 of the overfill prevention device 2 and the liquid level display device 3 to constitute the DME fuel tank float 10 of the present invention. In this embodiment, the overfill prevention device 2 and the liquid level display device 3 are connected to the hollow body 12 having the same configuration, and the DME fuel tank float 10 has the same configuration.

  In the hollow body 12 constituting the DME fuel tank float 10, as shown in FIG. 3, a cylindrical outer shell body portion 13 and shielding portions 14, 14 that shield both ends of the outer shell body portion 13. It is configured. The hollow body 12 is provided with a central tube portion 15 that forms a through-hole 16 penetrating the hollow body 12 in the longitudinal direction along the cylindrical central axis. 14 is opened at the center. The hollow body 12 has an air space sealed inside an outer shell body portion 13, a central tube portion 15, and shielding portions 14 and 14.

  The hollow body 12 has four rib portions 21 extending in the radial direction from the outer surface of the central cylindrical portion 15 and reaching the inner surface of the outer shell body portion 13 at equal intervals in the circumferential direction. Each rim portion 21 is formed along the longitudinal direction of the hollow body 12, and the inner airspace is partitioned by the four rib portions 21 to form four airtight cavities 18, respectively. In addition, the hollow body 12 is provided with protruding portions 22 that protrude inward from the inner surface of the outer shell body portion 13 between the rib portions 21. Each protrusion 22 is formed over the longitudinal direction of the outer shell body 13 and has a role of improving the strength and rigidity of the hollow body 12.

  The through hole 16 of the hollow body 12 is set so that the diameter of the through hole 16 can be inserted through the tip portions of the arms 55 and 65 of the overfill prevention device 2 and the liquid level display device 3 described above. Further, one of the shielding portions 14 of the hollow body 12 is provided with anti-rotation protrusions 23 and 23 that protrude outward in the longitudinal direction from the outer surface thereof. The two anti-rotation projections 23 are arranged at an interval between which the arms 55 and 65 can be fitted. That is, the arms 55 and 65 are arranged between the two anti-rotation protrusions 23 along the outer surface of the one shielding part 14 of the hollow body 12, and further bent in the longitudinal direction to pass through the through hole 16. And the front-end | tip of the arms 55 and 65 which penetrated the through-hole 16 is caulked on the outer side of the other shielding part 14, and is supported. Thereby, the hollow body 12 is connected to the arms 55 and 65 so as not to move in the longitudinal direction with respect to the arms 55 and 65 and so as not to rotate in the circumferential direction. Thus, by preventing the hollow body 12 from rotating and moving, the hollow body 12 can be prevented from sliding relative to the arms 55 and 65. Therefore, it can suppress that the hollow body 12 and the arms 55 and 65 wear, and can prevent the durability fall by this wear. Therefore, the hollow body 12 can exhibit desired durability.

  Such a hollow body 12 is molded from a PPS resin or a synthetic resin containing the same as a main component based on the result of the immersion test described above. As a result, the hollow body 12 has an excellent barrier property against DME fuel, and even if the hollow body 12 is immersed in the DME fuel, the DME fuel never enters the hermetic cavity 18.

Next, one means for forming the hollow body 12 having the above-described configuration will be described.
In the present embodiment, the hollow body 12 is formed by injection molding a PPS resin or a synthetic resin. By this injection molding, a bottomed outer shell cylinder 25 having an opening 26 at one end and a disk-like lid 27 that shields the opening 26 are formed (see FIG. 4). And the hollow body 12 is formed by joining the cover body 27 to the opening part 26 of this bottomed outer shell cylinder 25. As shown in FIG.

  As shown in FIG. 4, the bottomed outer shell cylinder 25 includes a cylindrical outer shell body portion 13 and a shielding portion 14 that shields the other end of the outer shell body portion 13. Inside the shell body portion 13, a center tube portion 15, four rib portions 21, and four projecting portions 22 are provided. Further, as shown in FIG. 4B, the above-described rotation preventing projections 23 and 23 are also formed on the shielding portion 14 of the bottomed outer shell cylinder 25. In addition, the bottomed outer shell cylinder 25 provided with such each component is integrally molded by injection molding. On the other hand, the lid body 27 is formed with an opening portion 28 penetrating in the thickness direction at the center thereof. When the lid 27 is joined to the opening 26 of the bottomed outer shell cylinder 25, the opening 28 is joined to the end of the central cylinder portion 15 of the bottomed outer shell cylinder 25, It communicates with the through hole 16 of the central cylinder portion 15.

  The above-described hollow body 12 (see FIG. 3) is formed by joining the above-described bottomed outer shell cylinder 25 and the lid body 27 by ultrasonic fusion. For this joining, the outer peripheral end of the lid 27 is bonded to the peripheral end of the opening 26 of the bottomed outer shell cylinder 25, and the hole peripheral end of the opening portion 28 of the lid 27 is connected to the bottomed outer shell. It adheres to the end of the central cylinder 15 of the cylinder 25. Thereby, the air space between the outer shell body portion 13 and the center tube portion 15 of the bottomed outer shell cylindrical body 25 is sealed, and four airtight void portions 18 partitioned by the four rib portions 21 are formed. . Thus, the hollow body 12 of the above-described embodiment is formed. Here, the lid body 27 shields the opening 26 of the bottomed outer shell cylinder 25 and becomes a component of the hollow body 12, and is a hollow formed by joining to the bottomed outer shell cylinder 25. It is in the body 12 and constitutes one of the shielding portions 14 (see FIG. 3).

  Further, in the present embodiment, the protruding portion 22 formed on the bottomed outer shell cylinder 25 is formed with a relief portion 24 having an inwardly inclined shape at the end on the opening side. The escape portion 24 is provided so that the end portion of the protruding portion 22 does not come into contact with the lid body 27. The purpose of this is to avoid stress concentration, because if the end portion of the protruding portion 22 and the lid 27 are formed so as to be in contact with each other, stress is concentrated on the contacted portion. And by avoiding stress concentration in this way, the strength and rigidity of the hollow body 12 can be sufficiently exhibited.

  The method of forming the hollow body 12 in this way is a method in which the bottomed outer shell cylinder 25 and the lid body 27 are injection-molded and joined to each other. However, it has the advantage that it can be molded easily and stably.

  As described above, the hollow body 12 formed in this way is connected to the arms 55 and 65, thereby being disposed in the overfill prevention device 2 and the liquid level display device 3 for the DME fuel tank according to the present invention. Used as float 10. The DME fuel tank float 10 and the overfill prevention device 2 and the liquid level display device 3 are disposed in the fuel tank 1 for storing the DME fuel. According to the liquid level, the DME fuel tank float 10 floats, and the liquid level of the DME fuel can be measured accurately and stably.

Next, the hollow body 12 constituting the DME fuel tank float 10 of this embodiment will be described in more detail.
The hollow body 12 is formed with an outer diameter of 40 mm, a length of 100 mm, and a plate thickness of 1.5 mm. Furthermore, the hole diameter of the through-hole 16 of the center cylinder part 15 is 3.5 mm, and the plate thickness of each rib part 21 is 1.5 mm. Moreover, the thickness of the protrusion part 22 is 1.5 mm, and the protrusion length is 2 mm. Further, the projection length of the anti-rotation projection 23 is 3 mm, and the distance between the two anti-rotation projections 23 is 3.5 mm.

As described above, the hollow body 12 is molded by ultrasonically welding the bottomed outer shell cylinder 25 and the lid 27 obtained by injection molding of the PPS resin. Here, the PPS resin has a density of 1.35 g / cm ³ and a tensile yield strength of 90 MPa. And when the specific gravity of this hollow body 12 is measured, it is 0.37, and since it is lower than the density of DME fuel 0.67 g / cm ^3, it is clear that it floats on the liquid surface of DME fuel. In addition, if it connects with each arm 55,65 of the overfill prevention apparatus 2 mentioned above or the liquid level display apparatus 3, the weight of this arm 55,65 will also act, However, The specific gravity of this hollow body 12 is DME fuel. Since it is sufficiently lower than the density of the liquid, it can float stably on the liquid surface.

  Moreover, when the compressive strength of said hollow body 12 was measured, it was 3 Mpa or more, and it has confirmed that the said hollow body 12 had sufficient compressive strength. Here, the fuel tank 1 for storing the DME fuel is recognized as a product mounted on the vehicle by following the high-pressure gas safety regulations. According to this high-pressure gas safety regulation, it is specified that the pressure resistance test pressure of the fuel tank storing DME fuel is 1.8 MPa or more. Therefore, even when the hollow body 12 of the present embodiment is used as a float of the overfill prevention device 2 or the liquid level display device 3, it can sufficiently withstand the internal pressure generated in the fuel tank of DME fuel. The pressure strength of the hollow body 12 was determined by a pressure test. In this pressure resistance test, a predetermined sealed container is filled with water, and after the hollow body 12 is placed, nitrogen gas is blown into the sealed container to improve the internal pressure and apply an external pressure to the hollow body 12. Then, the pressure when the hollow body 12 is broken is measured, and the pressure is obtained as the pressure resistance of the hollow body 12.

  As described above, the hollow body 12 of the present embodiment is formed by the PPS resin into the above-described configuration, so that it floats on the liquid surface of the DME fuel and can sufficiently withstand the internal pressure of the fuel tank 1. That is, the hollow body 12 has a hollow cylindrical shape and includes a plurality of rib portions 21, thereby achieving a desired specific gravity (0.5 or less) and pressure strength (1.8 MPa or more). .

  Moreover, the above-mentioned hollow body 12 was immersed in the predetermined container filled with DME fuel, and the immersion test which measures the weight increase was implemented. In this immersion test, an internal pressure of 1 MPa is applied to the container, the specimen is taken out after being immersed for 500 hours, and a change in weight relative to that before immersion is measured. For comparison, an immersion test was also performed on a float made of the above-described conventional foamed nitrile rubber. As a result of this immersion test, the hollow body 12 of this example hardly increased in weight relative to the weight before immersion. On the other hand, the foamed nitrile rubber float of the comparative example increased by about 1.6 times the weight before immersion. From this immersion test, it is clear that the hollow body 12 of this example has an extremely high barrier property that hardly penetrates DME fuel.

  From the above, the hollow body 12 of the present embodiment has a relatively long period of time when used as the DME fuel tank float 10 provided in the above-described overfill prevention device 2 or liquid level display device 3. Thus, the liquid level of the DME fuel in the fuel tank 1 can be floated accurately and stably. In the case of the overfill prevention device 2, the liquid level height that has reached the maximum filling amount by the DME fuel tank float 1 can be measured stably and accurately, so that the maximum filling amount is exceeded over a long period of time. Thus, it is possible to reliably prevent the DME fuel from being filled. In the case of the liquid level display device 3, the DME fuel tank float 10 can measure and display the liquid level height of the DME fuel in the fuel tank 1 stably and accurately.

In the above-described embodiment, the hollow body 12 constituting the DME fuel tank float 10 is molded from PPS resin, but the hollow body is molded from a synthetic resin mainly composed of PPS resin. You can also. For example, a hollow body is formed using a synthetic resin containing glass fibers in a PPS resin. The synthetic resin in this case has a glass fiber content of 30 to 50% by weight and a density of 1.57 to 1.75 g / cm ³ . And when a hollow body having the same shape as described above is molded with this synthetic resin, the specific gravity is 0.43 to 0.48. Even in a hollow body molded with such a synthetic resin, the density of the DME fuel is lower than that of the DME fuel, so that it can float on the surface of the DME fuel. Further, since the synthetic resin is mainly composed of PPS resin, it has a high barrier property against DME fuel. Furthermore, by containing glass fiber, the tensile yield strength is higher than that of the PPS resin, and the pressure resistance of the hollow body is also improved. From the above, even in the DME fuel tank float made of a hollow body formed of a synthetic resin containing glass fibers, the same effects as those of the above-described embodiment can be exhibited.

  In addition, as a synthetic resin which has PPS resin as a main component, it is also possible to contain a carbon fiber other than the above-mentioned glass fiber, for example. Even with such a synthetic resin, it is possible to obtain a DME fuel tank float that exhibits the same effects as described above.

  In the above-described embodiment, the hollow body 12 constituting the DME fuel tank float 10 has a hollow cylindrical shape and includes the four rib portions 21 therein. It is good also as a structure changed suitably. For example, it can be set as the structure provided with five rib parts at equal intervals in the circumferential direction.

  In the above-described embodiment, the hollow body 12 disposed in the overfill prevention device 2 and the liquid level display device 3 has the same configuration, but the configuration of the hollow body is different for each device. It can also be. That is, the structure of the DME fuel tank float may be different between the overfill prevention device 2 and the liquid level display device 3.

  In the above-described embodiments, the fuel tank 1 for DME fuel mounted on a truck has been described. However, the present invention can also be applied to fuel tanks mounted on various vehicles such as passenger cars and buses. . Even in various vehicles equipped with a fuel tank for storing DME fuel, the same effects as those of the above-described embodiment can be obtained.

  The present invention is not limited to the above-described embodiments, and can be appropriately used within the scope of the gist of the present invention. For example, assuming a fuel tank with the same shape as an LPG fuel tank for automobiles, the hollow body can be configured to have a maximum outer diameter of 45 mm and a maximum length of 200 mm in the manufacturing process. It is. And when the plate | board thickness of a hollow body is the same as the said dimension (1.5mm), since the specific gravity of a hollow body falls by enlarging an outer diameter or length, especially from the synthetic resin containing glass fiber. It works favorably in the molded one, and the stability of floating at the liquid level is further increased. Further, if the plate thickness is increased in consideration of the decrease in specific gravity, a higher pressure strength can be obtained.

It is sectional drawing of the fuel tank 1 mounted in a truck. It is explanatory drawing showing the (A) filling possible state of the mechanical overfilling prevention apparatus 2 provided in the fuel tank 1, and the (B) filling completion state. It is (A) longitudinal cross-sectional view of the hollow body 12 which comprises the float 10 for DME fuel tanks, (B) Side sectional view, (C) Side view. It is (A) perspective view and (B) longitudinal cross-sectional view of the bottomed outer shell cylinder 25 and the cover body 27 for shape | molding the hollow body 12. FIG.

Explanation of symbols

1 Fuel tank 2 Overfill prevention device
DESCRIPTION OF SYMBOLS 3 Liquid level display apparatus 10 DME fuel tank float 12 Hollow body 13 Outer shell body part 14 Shielding part 15 Central cylinder part 16 Through-hole 18 Airtight empty part 21 Rib part 22 Projection part 24 Escape part 25 Bottomed outer shell cylinder body 26 Opening 27 Lid

Claims (6)

In a DME fuel tank float that floats according to the liquid level of the DME fuel, which is disposed in a liquid level display device and / or an overfill prevention device provided in the fuel tank that stores the DME fuel,
It is formed of a hollow body having an airtight void formed by a PPS resin or a synthetic resin material containing the same as a main component, the specific gravity of the hollow body is 0.5 or less, and the pressure strength is 1.8 MPa or more. There is a float for a DME fuel tank. The PPS resin or a synthetic resin material containing the PPS resin as a main component has a density of 1.35 to 1.75 g / cm ³ and a tensile yield strength of 90 MPa or more. DME fuel tank float. The hollow body has a hollow cylindrical shape having a cylindrical outer shell body,
A central cylindrical portion that forms a through-hole penetrating along the cylindrical central axis, and a plurality of rib portions that extend from the outer surface of the central cylindrical portion along the radial direction to reach the inner surface of the outer shell barrel portion. The float for a DME fuel tank according to claim 1 or 2, wherein the DME fuel tank float is provided.   The hollow body includes a cylindrical outer shell body and shielding portions that shield both ends thereof, and two anti-rotation protrusions that protrude outwardly are arranged in parallel on one shielding portion. The float for a DME fuel tank according to claim 3, wherein the float is provided.   The hollow body is formed by joining a bottomed outer shell cylinder having an opening at one end and a lid for shielding the opening of the bottomed outer shell cylinder. Or the float for DME fuel tanks of Claim 4.   The bottomed outer shell cylinder includes a plurality of projecting portions projecting inwardly from the inner surface of the outer shell body portion between the rib portions, and the projecting portions are provided with lids on the end portions on the opening side. 6. The float for a DME fuel tank according to claim 5, wherein an escape portion that does not contact the body is formed.

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