JP2016113017A - Vehicular fuel tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel tank that can prevent fuel leakage even if deformed due to collision with rock fall, etc. and can be reduced in the weight without causing drastic change and increase of design and construction.SOLUTION: In a vehicular fuel tank 30 formed of a steel plate and suspended under the floor of a vehicle by a mounting frame and a fastening band, a coating material formed by adding predetermined amount of a non-halogen amino phosphoric acid flame retarder to a mixture of polyurethane resin and polyurea resin is applied to a predetermined portion of an outer surface so as to form predetermined film thickness. The predetermined portion is a portion of the outer surface excluding portions with which the mounting frame and the fastening band come contact, and is located in a range excluding the upper surface of the tank and a portion within 300 mm from the underfloor surface of the side surface of the tank.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fuel tank for a vehicle, in particular, a fuel tank for a pneumatic vehicle, and relates to a technique that is effective when applied to prevention of liquid leakage accompanying tank damage caused by the involvement of obstacles such as falling rocks or the raising of crushed stones.

  Conventionally, there has been an accident in which a fuel vehicle equipped with a fuel tank collides with a stone that has fallen on a railroad and rides on it, causing fuel to leak. However, the conventional fuel tank fuel tank structure is a structure in which steel plates are simply assembled in a box, which is easily damaged by the impact of falling rocks, etc., and in recent years, the weight of the tank has been reduced by reducing the thickness of the tank. There is a tendency to reduce the weight of fuel tanks for the purpose of reducing and improving running performance. For these reasons, it is necessary to take measures to prevent fuel leakage even when a rock falls and gets on.

  By the way, as a technique for preventing fuel leakage from the fuel tank, for example, a bag that covers and seals the tank is provided, and a nitrogen cylinder is connected to the bag to fill the inside of the bag portion with nitrogen. An invention has been proposed in which a valve of a nitrogen cylinder is opened when leakage occurs (see Patent Document 1). In addition, as a technique for improving the flame resistance of a fuel tank, for example, an invention for protecting by forming a ceramic coating film on the surface of the tank has been proposed (see Patent Document 2).

JP-A-10-258893 JP 2001-260667 A

  However, the invention described in the above-mentioned Patent Document 1 is applied to a fuel tank of a pneumatic vehicle with a height limited from the road surface as the device becomes large and the weight of the entire device increases. Have difficulty. Moreover, in order to reduce the weight of the tank, the invention described in the above-mentioned Patent Document 2 forms the ceramic coating film by applying a ceramic paint to the outer surface of the tank and forming the ceramic coating film on the outer surface of the tank. The flame resistance of the fuel tank is enhanced, and the ceramic coating is a brittle material. Therefore, as in the example described in the publication, the film thickness is thin (60 μm) and it is damaged by collision with falling rocks etc. On the other hand, when the film thickness is increased, there is a problem that the weight increases.

In addition, since diesel vehicles often travel in non-electrified sections with a relatively small number of passengers, it is difficult to make significant investments by improving the fuel tank itself in order to ensure profitability in business. .
The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a fuel tank capable of preventing fuel leakage even when deformed by collision with falling rocks or the like.
Another object of the present invention is to provide a fuel tank that can be reduced in weight without causing a significant change in design or construction, or an increase.

In order to achieve the above object, the invention of the present application is
In a fuel tank for a vehicle formed of a steel plate and suspended by a mounting frame and a fastening band under the floor of the vehicle,
A coating formed by adding a predetermined amount of a non-halogen aminophosphoric acid flame retardant to a mixture of polyurethane resin and polyurea resin at a predetermined site on the outer surface is applied so as to have a predetermined film thickness. is there.
According to this invention, the fuel tank is deformed by collision with falling rocks, etc., and even if a hole is made in the steel plate as the base material, the coating film applied to the surface is not broken, so that the tank causes fuel leakage. Can be prevented.

Here, when the thickness of the steel sheet is 1.6 mm, the predetermined film thickness of the paint is 4 mm or more in a dry state. Even when the thickness of the steel plate is 1.6 mm or more, a protective film having a thickness of 4 mm or more may be formed in a dry state.
It is applied even when a vehicle with a fuel tank under the floor collides with a fallen rock of the expected size while traveling at a speed of about 60 km / h by setting the coating film thickness to 4 mm or more. It is possible to prevent the tank from leaking fuel without tearing the coating film.
The upper limit of the coating film thickness is not in terms of tank strength, but the distance between adjacent underfloor equipment may be relatively narrow (for example, 1 cm) depending on the train to be applied. The upper limit value of the film thickness is preferably set to be equal to or smaller than the smallest interval among the intervals between the fuel tank and the adjacent underfloor device. Alternatively, when reducing the weight of the fuel tank by reducing the thickness, determine the film thickness so that the total weight of the paint to be applied is less than or equal to the weight reduced by reducing the thickness of the tank steel plate. May be.

Desirably, the predetermined portion is a range obtained by removing a portion of the outer surface within 300 mm from the upper surface of the tank and the floor lower surface of the side surface of the tank.
Underfloor equipment other than the fuel tank is provided in the area within 300mm from the bottom surface of the floor, so it is necessary if the paint is applied to the area of the tank surface excluding the area within 300mm from the bottom surface of the tank. Without applying the above paint, it is possible to prevent the fuel tank from leaking fuel due to a collision with falling rocks or the like.

Further preferably, the predetermined portion is a portion of the outer surface of the tank excluding a portion where the mounting frame contacts and a portion where the fastening band contacts, or a portion of the outer surface where the mounting frame contacts and tightening It is a part excluding the part in contact with the band and excluding the part within 300 mm from the upper surface of the tank and the floor lower surface of the side surface of the tank.
Since the paint is elastic with a material containing bubbles, thinning may occur over time, so when the paint is applied to a part of the surface of the fuel tank that contacts the mounting frame or band, Although the band tightening force may be reduced due to the thinness of the paint, applying the paint to the part of the outer surface excluding the part where the mounting frame and the tightening band are in contact makes the tank mounting state unstable. Can be avoided.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel tank which can prevent damaging by a collision with falling rocks etc. and causing a fuel leak is realizable. Further, there is an effect that the fuel tank can be reduced in weight without causing a significant change in design, construction, or increase.

It is the top view and front view which show the structural example of the static load test apparatus used in order to investigate the effectiveness of the fuel tank which concerns on this invention. It is the front view which shows the structural example of the falling weight impact test apparatus used in order to investigate the effectiveness of the fuel tank which concerns on this invention, and the perspective view which shows the shape of the fall sleeper used. 1 is a side view showing an embodiment of a fuel tank according to the present invention. It is a figure which shows an example of the application | coating area | region of the coating material in the fuel tank which concerns on this invention.

Hereinafter, an embodiment of a fuel tank according to the present invention will be described with reference to the drawings.
The present inventors have conducted various studies on a fuel tank that does not cause fuel leakage even when it collides with an obstacle such as rock fall. As a result, in order to prevent fuel leakage due to collision with falling rocks, etc. while reducing the weight without causing significant design or construction changes or increases, a paint film (hereinafter referred to as protection) that has a spreadability on the surface of the fuel tank. The idea was that it would be optimal to form a film). Therefore, various paints were tested to examine the relationship between film thickness, load bearing performance and impact resistance performance.

  In addition, when we examined the damage of the fuel tank of a vehicle that had caused an accident in the past, it is necessary to form a protective film on the entire surface of the fuel tank in order to prevent fuel leakage because the damage is limited. On the other hand, in order to reduce the weight of the fuel tank, the idea that it is desirable to limit the range in which the protective film is formed was obtained. Then, as a result of examining the range in which the protective film is formed, the inventors have arrived at the invention according to the present application.

Hereinafter, among the tests conducted by the present inventors, test results and discussion results related to the invention of the present application will be described. Here, first, the test results and the discussion results on the relationship between the film thickness of the paint formed on the surface of the fuel tank, the load bearing performance and the impact resistance performance will be explained, and then the scope of the formation of the protective film will be discussed. explain.
The paint applied to the surface of the fuel tank has been studied for its properties (extensibility, flame retardancy, etc.) for various paints. As a result, polyurethane resin and polyurea resin are mixed with non-halogen aminophosphate. The conclusion was reached that a paint (referred to as paint X) to which a predetermined amount of a flame retardant has been added is optimal. In the following description, when “paint” is simply described, this paint X is meant.

  The present inventors have shown in FIG. 1 a plurality of test pieces in which protective films having different thicknesses are formed on the surface of a 1.6 mm thick SECC (electrogalvanized steel plate), which is a material for a fuel tank of a Kiha 110 series train. A static load test using a static load test apparatus configured as shown in FIG. 2 and an impact test using a falling weight impact test apparatus configured as shown in FIG. FIG. 2 shows the test results performed using the static load test apparatus of FIG. 1, and FIG. 7 shows the test results performed using the falling weight impact test apparatus of FIG. The test piece subjected to the static load test is a rectangular steel plate having a thickness of 1.6 mm and a size of 297 mm × 420 mm. The drop weight impact test is performed in the range from the bottom surface to the 200mm height position of the bottom surface and outer peripheral surface of a 1.6mm-thick steel plate drum (diameter 60cm) that has almost the same material and thickness as the fuel tank. The test was performed on a protective film formed.

A static load test apparatus 10 shown in FIG. 1 is installed on a base 11 having a rectangular steel base, a load cell 12 for load measurement installed at the center of the base 11, and the load cell 12 interposed therebetween. A U-shaped support base 13 having a pair of support legs, a rectangular frame-shaped contact plate 14 placed on the support base 13, and a corresponding contact plate 14 having the same shape as the plate 14. A holding frame 15 for holding a test piece S having a protective film formed on a steel plate therebetween, a plurality of clamping bolts 16 for fixing the holding frame 15 and the contact plate 14 to the upper surface of the support base 13, and the load cell 12 And a load body 18 coupled to the tip of the jack 17 and a wire displacement meter 19 provided on the load body 18.
An opening is provided in the upper wall portion of the support base 13 so as to correspond to the rectangular frame-shaped contact plate 14, and the arrangement of each member is set so that the tip of the load body 18 is desired in the opening. The load body 18 has a shape in which a cylindrical portion is formed continuously at a lower portion of a truncated conical body having a circular surface having a diameter of 20 mm at the upper end (hereinafter referred to as a pressing surface).

In the static load test, the test piece S is sandwiched between the backing plate 14 and the presser frame 15 and fixed with the fastening bolts 16, the jack 17 is operated, and the load body 18 is moved upward to test the test piece S. A load is applied to the lower surface of the steel plate from below, the load is increased until the steel plate and the protective film are broken, and the load and the amount of displacement are measured by the load cell 12 and the displacement meter 19.
The inventors of the present invention have used the above-described static load test apparatus 10 to provide a mixed paint of 1.6 mm-base steel sheet, polyurethane resin and polyurea resin to which no flame retardant has been added to a thickness of 2 mm, 4 mm, and 6 mm. The test piece that was applied to form a protective film and the test piece that was applied to a 1.6 mm steel plate with the newly developed paint X in a dry state to a thickness of 4 mm and 6 mm and dried to form a protective film were described above. A static load test was performed with the static load test apparatus 10.

Table 1 shows the results of the static load test.

  Table 1 shows that when the base steel sheet and the steel sheet on which the protective film is formed are compared, the steel sheet on which the protective film is formed has a larger breaking load. In addition, regarding the thickness of the protective film, it can be seen that the breaking load increases and the strength increases according to the film thickness. Regarding the displacement up to the break, it can be seen that the steel plate with the protective film formed thereon also increases the displacement up to the break compared to the base steel plate. Furthermore, it can be seen from Table 1 that the breaking load does not change greatly, that is, there is no decrease in strength due to the addition of the flame retardant, whether the flame retardant is added or not.

From the above, it became clear that the strength of the steel plate against static load is improved by applying a paint mixed with polyurethane resin and polyurea resin to 1.6 mm steel plate as the fuel tank material. It was. In addition, since there was no decrease in strength due to the addition of the flame retardant, it was concluded that the protective film formed by applying the paint X to which the flame retardant was added was less likely to burn and was desirable for the fuel tank.
However, considering the situation where rock falls etc. collide with the diesel car, it is considered that the rock fall etc. will collide with the fuel tank with a stronger impact when the diesel car is running, so it should be applied to the fuel tank mounted on the diesel car. When thinking, verification by a static load test is not enough. Therefore, the present inventors performed an impact load test that reproduced a collision with speed on the test piece.

As shown in FIG. 2 (A), the drop weight impact test apparatus 20 includes a work gantry 21 having a height of 12 m constructed of a steel pipe 21a and a steel plate 21b to be used as a scaffold, and a drop having a weight of 27.8 kg. A guide tube 23 made of vinyl chloride is provided to guide the sleeper 22 and the falling sleeper 22 held free in the center of the work gantry 21. The ground below the guide tube 23 has a thickness of about 50 cm and is 2 m × 2 m. A rectangular concrete base 24 having a size of 1 mm is provided.
The falling weight impact test is performed by placing a drum 40 having a protective film formed from the bottom to the side on the concrete foundation 24 with the bottom facing up.

  As shown in FIG. 2 (B), the falling sleeper 22 has a large-diameter cylindrical portion 22b having a diameter of 136 mm continuous with a base portion of a truncated cone 22a having a pressing surface having a circular shape with a diameter of 20 mm at the tip. Furthermore, the small diameter cylindrical part 22c with a diameter of 200 mm is formed so as to be continuous. The weight is 27.8kg. Various falling weights such as a spherical weight and a U-shaped tip are known as falling weights used in the falling weight impact test. The reason for selecting such a shape and weight is that the fuel tank breakage that occurred in the past and the ease of testing were taken into consideration.

  The inventors of the present invention have used the falling weight impact test apparatus 20 to prepare a mixed can (a paint X developed this time) of a drum can made of a 1.6 mm body steel plate, a polyurethane resin and a polyurea resin to which a flame retardant is added. Drum cans with a 4mm thickness and a protective film formed from the bottom to the side (in the range of 200mm), and drums with a 1.6mm steel plate coated with the newly developed coating X to a thickness of 6mm. The drop weight impact test was performed using the above-described drop weight impact test apparatus 20 with various drop distances. In addition, about 1/4 of the volume of water was placed in the drum can to prevent overturning when applying an impact.

Table 2 shows the results of the falling weight impact test. In Table 2, a circle mark in the damage status column means that no hole has occurred, and a cross mark means that a hole has occurred.

By the way, the magnitude of the collision can be compared by impulse, but since the acting time is very short in the impact assumed this time, the momentum before and after the collision is changed, and the velocity of the falling weight is 0 m / s due to the collision. Assuming that, the following equation (1) can be obtained. In Equation (1), m is the mass of the falling weight, and ν _c is the velocity at the time of collision.
mν _c −m · 0 = mν _c ...... Equation (1)

Also, the collision velocity ν _c can be _calculated by the following formula (2) from the formula of the energy conservation law of free fall assuming that the resistance of air is negligible. The impulse I is the square root of the fall distance from the formula (3). It turns out that it is proportional to. In addition, g is a gravitational acceleration and h is a fall distance.
mgh = (1/2) mν _c ²
ν _c = √2gh …… Formula (2)
I = mν _c = √2 m ² g × √h∝√h ...... Equation (3)
Table 2 shows a value obtained by calculating the impulse I corresponding to the drop distance in the drop weight impact test using the above formula (3).

According to Table 2, the base drum can not make a hole until the drop distance is 1.00m, but the hole is opened at the drop distance of 1.25m. In addition, when the protective film is formed to a thickness of 4 mm, the steel plate does not open a hole up to a drop distance of 3.00 m, but neither the steel plate nor the protective film has a hole. However, it was found that the protective film did not open at the fall distance of 3.50m, and the hole opened at the drop distance of 4.00m. Similarly, when the protective film was formed to a thickness of 6 mm, it was found that the steel sheet can withstand a drop distance of 5.00 m and the protective film can withstand a drop distance of 7.00 m.
The present inventors examined the range of the optimum thickness of the protective film of the paint X formed on the fuel tank mounted on the diesel car from the result of the drop weight impact test. In this study, we referred to accidents involving fuel leaks that occurred in the past.

In the fuel tank damage accident of Kiha 40 type diesel car that occurred on the Banetsu West Line in October 2012, 160kg Kasaishi (from the photo etc., about 530mm × 400mm × 300mm, rail direction 530mm, height 400mm, sleeper direction 300mm ) Collided with the fuel tank and a fuel leak occurred. As for the magnitude of the force when the capstone collides with the fuel tank, it is necessary to consider the weight of the area that directly hits the tank in consideration of the volume that escapes under the floor and the escape of impact caused by rolling. The total height of the collision is 370.16mm when the height of the rail (50kg rail) is 144.46mm and the height from the rail upper surface to the bottom of the tank lower part is 225.7mm. Therefore, the weight of the area where the capstone directly hits the tank can be estimated as follows.
(400−370.16) × 1000 × 0.53 × 0.30 × 2600 = 12.3kg
From this weight, the impulse when the diesel car is traveling at 60 km / h can be estimated as follows.
60 × 1000/3600 = 16.7m / s
16.7 × 12.3 = 205.4Ns

From the results obtained in the drop weight impact test, the base drum can withstand a drop from 1.00 m (impact 122.2 Ns), but not from 1.25 m (impact 136.6 Ns). On the other hand, it was found that when a protective film of 4 mm was formed on the drum, it could withstand up to 3.00 m (improvement of 211.6 Ns). This impulse is considered to be effective because the magnitude of the impact at the time of the accident is larger than 205.4, that is, 25.4 <211.6. Therefore, it was concluded that the thickness of the protective film should be 4 mm or more.
The above conclusion was derived based on the results of the above test conducted on a fuel tank made of a steel plate having a plate thickness of 1.6 mm. Therefore, for a fuel tank made of a steel plate thicker than 1.6 mm, if a similar protective film is formed on the surface of 4 mm or more, the strength is higher than that of a fuel tank made of a steel plate with a thickness of 1.6 mm. It is clear that fuel leakage can be prevented against a large impact. Therefore, a protective film of 4 mm or more may be formed on the surface of a fuel tank made of a steel plate thicker than 1.6 mm.

In addition, the greater the thickness of the protective film, the greater the product that can be withstood. However, when the dimensions of the fuel tanks of various types of diesel vehicles were examined, many other devices besides the fuel tank were placed under the vehicle floor. Since the smallest distance between the fuel tank and other underfloor equipment is 10.0 mm, the upper limit value of the thickness of the protective film is preferably 10.0 mm.
In addition, since the paint is applied to prevent fuel leakage due to damage to the steel plate accompanying the weight reduction of the tank, for example, when it is desired to reduce the weight by reducing the thickness of the fuel tank, You may determine a film thickness so that the total weight of the coating material to apply | coat may be below the weight reduced by making the steel plate of a tank thin.

Specifically, the mass per unit area of the protective film from the measured such specimens, because it is about 14.1 kg / m ² in terms of 4 mm 56.4 kg / m ^2, i.e. 1mm thick in thickness, by the method described later If the coating area to be determined is 0.215 m ² , the mass increases by 3.03 kg per 1 mm thickness. On the other hand, the fuel tank of Kiha 40 type diesel car is made of 2.3mm thick steel plate and its weight is 82.0kg, so the weight per 0.1mm thickness is 3.565kg. Therefore, for example, when considering a case where a 2.3 mm thick steel plate is changed to a 1.6 mm thick steel plate with the same size and volume, the tank weight decrease is about 24.955 kg, so the coating area is 0.215 m ² . Assuming that the total thickness is the same as before the weight reduction even if the thickness of the protective film is increased by 8.23 mm, the upper limit value of the protective film thickness may be determined to be 8.23 mm.

  In addition, as described above, the present inventors investigated the damage of the fuel tank of the vehicle that had caused an accident in the past, and because the damaged part is limited to the bottom side of the tank, the fuel leakage was prevented. In order to prevent this, it is not necessary to form a protective film on the entire surface of the fuel tank. On the other hand, in order to reduce the weight of the fuel tank, it is desirable to limit the range in which the protective film is formed. We also studied.

Specifically, in order to make a fuel tank that has a function of preventing fuel leakage without greatly modifying the existing fuel tank,
1) Minimize additional work on the vehicle body and use the existing mounting method (mounting frame + tightening band) 2) Paint the existing diesel car as a model, with the requirement that the weight not increase significantly. The method was examined.

  Since the formation of a protective film for a fuel tank in a pneumatic vehicle is intended to prevent fuel leakage due to tank damage due to collision of falling rocks that have entered under the vehicle, it is only necessary to apply paint mainly on the bottom side of the tank. Therefore, in order to know the height at which application can be omitted, we investigated the height from below the floor of the equipment that becomes an obstacle before falling rock hits the fuel tank. As a result, the fuel tank 30 is suspended under the floor of the vehicle. From the arrangement of the underfloor equipment (for example, an air storage tank) in the rail direction around the fuel tank, as shown in FIG. Was found to be about 300 mm in height. Therefore, the range in the height direction in which coating of the paint on the fuel tank is omitted is set to be within 300 mm from below the floor.

As shown in FIG. 3, the Kiha E130 series fuel tank employs an attachment method in which the fuel tank 30 is placed on an attachment frame 31 suspended under the floor of the vehicle and fixed with a fastening band 32. On the other hand, since the paint forming the protective film examined this time is a material containing bubbles and is elastic, there is a possibility that thinning of the skin may occur over time. When this paint is also applied to the attachment frame 31 or the fastening band 32 on the surface of the fuel tank 30 and the contact area with the fastening band 32, it is considered that the tank attachment becomes unstable due to a decrease in the band fastening force due to thinning of the protective film. . Therefore, it was decided to avoid applying paint to the attachment frame and the part in contact with the band.
FIG. 4 shows the coating range determined in consideration of the above. In FIG. 4, the hatched portion is the paint application range. In addition, the part to which 30a is attached | subjected is the fueling opening of a fuel tank.

Although the invention made by the present inventor has been specifically described based on the embodiment, the present invention is not limited to the embodiment. For example, in the above embodiment, the coating area on the surface of the fuel tank for forming the protective film is within 300 mm from below the floor and the range excluding the mounting frame and the tightening band and the contact area, but is in contact with the mounting frame and the tightening band. Paint may be applied to the part, and only the area within 300 mm from the floor may be removed.
In the above-described embodiment, the present invention is applied to a fuel tank for a pneumatic vehicle. However, the present invention is not limited to a fuel tank for a pneumatic vehicle, and is widely applied to a fuel tank for a vehicle equipped with an engine such as a truck or a camper. Can be applied.

DESCRIPTION OF SYMBOLS 10 Static load test apparatus 12 Load cell 13 Support stand 14 Suspension plate 15 Holding frame 17 Jack 18 Load body 19 Wire displacement meter 20 Drop weight impact test apparatus 21 Work gantry 22 Fall sleeper 23 Guide pipe 24 Concrete foundation 30 Fuel tank 31 Mounting frame 32 Tightening band

Claims (5)

A fuel tank for a vehicle formed of a steel plate and suspended by a mounting frame and a fastening band under the floor of the vehicle,
A paint obtained by adding a predetermined amount of a non-halogen aminophosphoric acid flame retardant to a mixture of a polyurethane resin and a polyurea resin is applied to a predetermined portion of the outer surface so as to have a predetermined film thickness. Vehicle fuel tank.   2. The vehicle fuel tank according to claim 1, wherein when the thickness of the steel plate is 1.6 mm or more, the predetermined film thickness is 4 mm or more in a dry state.   3. The vehicle fuel tank according to claim 1, wherein the predetermined portion is a range excluding a portion within 300 mm from an upper surface of the tank and a floor lower surface of a side surface of the tank of the outer surface. .   3. The vehicle fuel tank according to claim 1, wherein the predetermined part is a part of the outer surface of the tank excluding a part in contact with the mounting frame and a part in contact with the tightening band.   The predetermined portion is a portion of the outer surface of the tank excluding a portion where the mounting frame contacts and a portion where the fastening band contacts, and a portion within 300 mm from the upper surface of the tank and the floor lower surface of the side surface of the tank The fuel tank for vehicles according to claim 1 or 2, wherein the fuel tank for vehicles is excluded.

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