This application is a divisional of patent Ser. No. 09/630,417 filed Aug. 1, 2000, U.S. Pat. No. 6,390,124.

FIELD OF THE INVENTION

The present invention relates to a fuel inlet for pouring fuel into a fuel tank of a car and the like, and a manufacturing method thereof.

BACKGROUND OF THE INVENTION

Generally, when pouring fuel such as gasoline into a fuel tank of a car and the like, a fuel inlet 701 as shown in FIG. 31 is used. A connecting pipe J is fixed to the end of the fuel inlet 701 on the fuel tank side, and a breather tube 703 communicating with the fuel tank T is provided in the vicinity of a fuel port 701a of the fuel inlet 701. At the time of fueling, a not shown fuel feeding nozzle is inserted into the fuel inlet 701 through the fuel port 701a and fuel is fed into the fuel tank T through the fuel inlet 701 and the connecting pipe J. When fuel feed into the fuel tank T starts, the air in the fuel tank T is pushed toward the fuel port 701a of the fuel inlet 701 through the breather tube 703. When fuel feed continues and a certain amount of the fuel is stored in the fuel tank T, the internal pressure of the fuel tank T increases and causes the fuel feed nozzle to automatically stop, and further automatic feeding is impossible. A person who feeds fuel notices it and shifts the feeding into manual operation, and additionally pours a small amount of gasoline two to three times before finishing the feeding.

The above process involves a problem that since the air pushed toward the fuel port while the feeding contains a high density of fuel vapor, careless emission thereof into the atmosphere leads to an increase of fuel density around and thus unfavorable effects on the environment.

To solve this problem, it is proposed to employ a fuel inlet 801 shown in FIG. 32. The fuel inlet 801 is provided with a relatively small diameter portion 806 within its fuel passage. Since a space 807 shown in cross section of the passage, when fuel fed at a specific rate passes the relatively small diameter portion 806, is made smaller than in a conventional fuel inlet, venturi vacuum is generated and negative pressure in the space 807 is increased. As a result, the air returning toward the fuel port from the fuel tank through the breather tube 803 is effectively prevented from being emitted into the atmosphere. This is called a liquid seal, which is one of the means in Onboard Refueling Vapor Recovery systems, or ORVRs.

However, if the fuel inlet 801 having a relatively small diameter portion 806 of 25.4 mm, for example, is produced as a solid one by pressing a blank pipe instead of connecting a plurality of members, one end of the blank pipe of 25.4 mm, i.e. the fuel port should be expanded to 48 mm to 60 mm, and such a large expansion often causes cracking. Also it is required that the breather tube 803 and the inlet pipe 802 be connected easily and securely and that a spiral groove be easily formed around the expanded end of the inlet pipe to allow a cap to be screwed thereon.

A fuel inlet, having a double structure in the vicinity of the fuel port formed by folding one end of the pipe inward, is known as disclosed in the Publication of Japanese Unexamined Patent Application No. 9-39591(Cf. FIG. 33B). This type of fuel inlet 901 obtains enough strength because of the double structure in the vicinity of the fuel port and has a great durability against abrasion due to opening/closing operation of the fuel port cap.

The above fuel inlet 901 is formed as follows: Firstly, as shown in FIG. 33A, a first taper portion 901a and a second taper portion 901b are formed. Secondly, the first taper portion 901a and the second taper portion 901b are folded back to the inside of the pipe (See dotted lines in FIG. 33A) by applying pressure P in the axial direction onto the open end of the second taper portion 901b. Then, the folded end is expanded and a groove 901c is formed. By forming the first taper portion 901a and the second taper portion 901b having different cone angles, respectively, and folding these taper portions, the bending region can be prevented from being applied an excessive load thereto.

Although the fuel inlet 901, wherein a double structure is provided in the vicinity of the fuel port by folding back the end of the pipe, is quite useful, it involves a problem that the manufacturing process thereof is complicated. These days a fuel inlet is sometimes provided with a retainer having an interference portion, but it makes the manufacturing process further complicated to produce such an inlet according to the method disclosed in the Publication of Japanese Unexamined Patent Application No. 9-39591. Attaching a separate retainer to the folded end is practical, and a synthetic resin retainer which is usually more expensive than a metal one is fixed in because it is difficult to attach a metal retainer to the folded end by crimping or welding.

Also known is a structure, as shown in FIG. 34, wherein a fuel inlet 1001 is forced and fixed into a fuel inlet supporting hole 1015 provided in a car body B (See Publication of Japanese Examined Utility Model Application No. 6-259, for example). Specifically, the fuel inlet 1001 having a synthetic resin cylindrical cover 1005 fitted on the outer circumference in the vicinity of the fuel port is forced into the fuel inlet supporting hole 1015 from the side of a fuel tank T, thereby the cylindrical cover 1005 is pressed against the fuel inlet supporting hole 1015. Since this structure enables relative movement between the car body B and the fuel inlet 1001, even if a heavy load is applied to the car body B, for example, the car body B yields or bulges independently of the fuel inlet 1001, and therefore the heavy load does not directly affect the fuel inlet 1001. Furthermore, even if the car body B is deformed to bulge toward the fuel inlet 1001, the bulging region does not cause the fuel port cap C to be pushed up and removed because the outer diameter of the fuel port cap C is designed to be smaller than the outer diameter of the cylindrical cover 1005.

The structure in FIG. 34, however, has a problem that the cylindrical cover 1005 made of synthetic resin leads to the higher cost of materials, which makes the cost for fixing the fuel inlet 1001 increased. Also, the cylindrical cover 1005 used as a separate member needs to be produced separately as well as requires another process step of attaching the same to the fuel inlet 1001, and as a result the cost for fixing the fuel inlet 1001 is further increased.

Moreover, this structure requires a retaining mechanism for preventing the cylindrical cover 1005 from being displaced axially relative to the fuel inlet 1001 when the fuel inlet 1001 with the cylindrical cover 1005 wrapped therearound is forced into the fuel inlet supporting hole 1015. Specifically, as shown in FIG. 34, the retaining mechanism is constituted by a bead 1001a provided on the outer circumference of the fuel inlet 1001 and a groove 1005a provided on the internal circumference of the cylindrical cover 1005 for catching the bead 1001a. This type of retaining mechanism complicates the structure of the fuel inlet 1001 and impedes production thereof.

SUMMARY OF THE INVENTION

Wherefore, a principal object of the present invention is to provide a fuel inlet which has a liquid seal function and whose production requires only a small number of parts and also is easy.

Another object of the present invention is to provide a fuel inlet which has a double structure in the vicinity of its fuel port and is easy to make.

Further object of the present invention is to provide a fuel inlet having a simple structure and not requiring high cost of fixing the same to a car body such that relative movement is allowed therebetween.

According to the first phase of the present invention, the fuel inlet comprises: an inlet pipe for guiding fuel into a fuel tank and a breather tube for letting the air out of the fuel tank toward the forward end portion of the inlet pipe while feeding fuel, one end of the inlet pipe being expanded to have a diameter one and a half to three times as large as the diameter of the body of the inlet pipe, and also being provided with a spiral groove directly formed therein, for engaging with a cap, an open end of the breather tube joined to the forward end portion of the inlet pipe being provided with a flange, which is projection welded on the area around a hole provided in the forward end portion of the inlet pipe.

The fuel inlet of the present invention is preferably made of a material selected from SUS304, SUS304L, SUS436 according to JIS, and their equivalents.

According to another phase of the present invention, the fuel inlet comprises: an inlet pipe for guiding fuel into a fuel tank; a cylindrical reinforcement overlapping the inner circumference of the inlet pipe in the vicinity of the fuel port thereof; and a screw portion for screwing a fuel port cap thereon formed by crimping the inlet pipe and the cylindrical reinforcement.

According to a further phase of the present invention, the fuel inlet is forced and fixed in a fuel inlet supporting hole provided in a car body such that relative movement between said fuel inlet and the car body is allowed. The fuel inlet comprises: an extending portion extending radially outward from the edge of an inlet pipe on the side where a fuel port cap is screwed; and an outer-cylinder-like flange adjoining the extending portion and having a configuration formed by being folded back in the axial direction of the inlet pipe, the outer-cylinder-like flange being fixed tight in the fuel inlet supporting hole when forced thereinto.

According to a still further phase of the present invention, the fuel inlet having liquid seal function comprises: a relatively large diameter portion formed on the side of a fuel port; and a relatively small diameter portion formed integrally with the relatively large diameter portion on the side of a fuel tank, the relatively small diameter portion having a diameter smaller than the relatively large diameter portion by being provided with a plurality of elongate protrusions having a configuration of being pinched from the outside.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a front view showing the expanded portion of a fuel inlet according to a first preferred embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line II of FIG. 1;

FIG. 3 is a front view of a pipe before forming a spiral groove therein;

FIG. 4 is an explanatory view showing how to form the spiral groove;

FIG. 5 is an explanatory view showing how to form the spiral groove in another way;

FIG. 6 is a cross-sectional view showing the connecting portion of a breather tube with an inlet pipe in the present invention;

FIG. 7 is a cross-sectional view showing how to form the connecting structure of FIG. 6;

FIG. 8 is a cross-sectional view taken along line 88 of FIG. 7;

FIG. 9 is a longitudinal cross-sectional view of the fuel inlet of the first embodiment with the expanded portion having a partial double structure;

FIG. 10 is an explanatory view showing how to produce the fuel inlet of FIG. 9;

FIG. 11 is a longitudinal cross-sectional view of the fuel inlet of the first embodiment having the expanded portion provided with an integral outer-cylinder-like flange;

FIG. 12 is a longitudinal cross-sectional view of the fuel inlet having the expanded portion provided with another integral outer-cylinder-like flange;

FIG. 13 is a perspective view of another outer-cylinder-like flange;

FIG. 14 is a longitudinal cross-sectional view of a further outer-cylinder-like flange;

FIG. 15 is a cross-sectional view of the fuel inlet having a characteristic structure of the first embodiment;

FIG. 16 is a perspective view of a fuel inlet according to a second embodiment of the present invention with a relatively small diameter portion formed by narrowing a pipe;

FIG. 17A is a cross-sectional view of the fuel inlet taken along line 17A17A of FIG. 16;

FIG. 17B is a cross-sectional view of the fuel inlet taken along line 17B17B of FIG. 16;

FIG. 18 is a schematic explanatory view showing a press used for producing the fuel inlet of FIG. 16;

FIG. 19 is a perspective view of a core material used for producing the fuel inlet of FIG. 16;

FIGS. 20-23 are explanatory views showing the state of the fuel inlet of FIG. 16 during production;

FIG. 24A is a longitudinal cross-sectional view of a modified narrowed fuel inlet;

FIG. 24B is a transverse cross-sectional view of the relatively small diameter portion;

FIG. 25 is a perspective view of a modification of the fuel inlet of the second embodiment;

FIGS. 26A-26C and FIGS. 27A-27D are schematic explanatory views showing how to produce the fuel inlet of FIG. 25 using plates having different thicknesses;

FIG. 28 is a perspective view of an inner die used for producing the fuel inlet of FIG. 25;

FIGS. 29A and 29B are explanatory views showing the state of the fuel inlet of FIG. 25 during production;

FIG. 30 is a detailed explanatory view showing the cross section of a mouthpiece portion of the fuel inlet of FIG. 25; and

FIGS. 31, 32, 33A, 33B and 34 are explanatory views showing fuel inlets related to prior art of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

In this embodiment, a fuel inlet is produced by expanding part of a pipe.

A fuel inlet 1 according to the present embodiment shown in FIGS. 1 and 2 is provided with a spiral groove 2a formed in a expanded portion 2 thereof. The expanded portion 2 is formed by increasing the diameter of an end by bulging.

The fuel inlet 1 is used for pouring fuel such as gasoline into a fuel tank of a car and the like. Except when fuel is being poured, the opening of the fuel inlet 1 is closed by screwing a cap 4 (see FIG. 2) having a screw portion 4a engageable with the spiral groove 2a.

It will be described how the fuel inlet 1 such as the above is produced with reference to FIGS. 3 and 4.

Firstly required is a blank pipe 10 shown in FIG. 3, which has an expanded portion 12 formed by increasing the diameter of one end thereof by bulging, the end of the expanded portion 12 being flared. The material of the pipe 10 is, for example, SUS304, SUS304L or SUS436 according to Japanese Industrial Standards or JIS. The diameter of the pipe 10 is 25.4 mm to 35 mm, and the diameter of the expanded portion 12 is 48 mm to 60 mm. In the present embodiment, very malleable SUS304, SUS304L or SUS436 is employed to prevent cracks during bulging by which the diameter of the pipe is increased about two and a half times. Another reason for employing a stainless pipe such as the above is to prevent rust.

Then, the outer circumference of the pipe 10 is securely held by a hydraulic clamp 30 as shown in FIG. 4. A core bar 32, which is fixed to a pipe end pressurizing die 31, is inserted into the expanded part 12 of the pipe 10. The core bar 32 is provided with an uneven portion 32a to form the spiral groove 2a. Specifically, the uneven portion 32a has approximately the same configuration as the outer circumference of the cap 4, i.e. the screw portion 4a.

In the above state, the roller surface of a roller 20 is pressed on the outer circumference of the expanded portion 12 of the pipe 10 while the roller 20 is rotated around the pipe axis C and at the same time gradually moved downward.

The roller 20 is rotatably held by a roller shaft 22 (approximately parallel to the pipe axis C) provided in a roller support 21. The roller support 21 is attached to a rotary body 5 rotatable around the pipe axis C such that the roller support 21 is movable by means of a hydraulic cylinder 23 in the radial direction of the rotary body 5.

When the roller support 21 is moved radially inward by the hydraulic cylinder 23, the roller 20 is moved in the same direction, with the result that the roller surface of the roller 20 is pressed on the outer circumference of the pipe 10. And when the rotary body 5 is gradually moved downward while rotating around the pipe axis C, the roller 20 is also gradually moved downward while pressing on the outer circumference of the expanded portion 12 of the pipe 10 and rotating around the pipe axis C.

As a result, the expanded portion 12 of the pipe 10 has been transformed to have a configuration corresponding to the uneven portion 32a of the core bar 32 when the roller 20 approaches the open end of the pipe 10 after moving gradually from the end of the core bar 32 downward.

Then the rotation of the rotary body 5 is stopped, the roller support 21 is moved radially outward by the hydraulic cylinder 23, and holding by the hydraulic clamp 30 is cancelled. Thus, the fuel inlet 1 of the present embodiment shown in FIGS. 1 and 2 is obtained.

In the present embodiment, the number of parts can be reduced because it is not necessary to prepare the expanded portion as a separate part. When a fuel inlet having an expanded portion with a different diameter is to be produced, it is only necessary to replace the core bar with another corresponding to the different diameter. Since the same roller can be used, such a fuel inlet can be produced efficiently. Also, an appropriate thickness of the plate can be obtained in the region where the spiral groove 2a is formed.

For producing the above fuel inlet 1, both a roughing roller 41 having a large roller width and a finishing roller 42 having a small roller width may be attached onto the rotary body 5. The roughing roller 41 and the finishing roller 42 are radially movable with respect to the rotary body 5 by the hydraulic cylinder, and the roughing roller 41 and the finishing roller 42 are interchangeable in their position.

The roughing roller 41 is for roughly forming the shape of the expanded portion 12 of the pipe 10, while the finishing roller 42 is for adjusting the shape of the expanded portion 12 of the pipe 10 to the configuration of the core bar 32 in detail. By using both of the roughing roller 41 and the finishing roller 42, the above described operation can be obtained more efficiently, compared with the case where only one roller is used.

Connection between the breather tube 110 and the inlet pipe 102 will now be described with reference to FIGS. 6-8.

The fuel inlet 101 according to the present embodiment comprises an inlet pipe 102, a feeding portion 104 and a breather tube 110.

The inlet pipe 102 is a cylindrical pipe introducing fuel into the fuel tank (hereinafter referred to as tank), and is provided with a flat attachment portion 102a to attach the breather tube 110 thereon and flat support portion 102b to enable easy support of the breather tube 110 during projection welding. Furthermore, the flat attachment portion 102a is provided with a hole 102c communicating with the breather tube 110.

Feeding portion 104 is formed by expanding an end of the inlet pipe 102, and is provided with a spiral groove 104b for engaging with a not-shown cap. The breather tube 110 is provided, at the open end 110c thereof, with a flange 110a, which is welded to the flat attachment portion 102a of the inlet pipe 102 by projection welding. The material for the inlet pipe 102 is also used for the breather tube 110 to avoid galvanic corrosion.

With the above fuel inlet 101 attached to a tank of a car, when gasoline is poured through a feeding nozzle inserted into the feeding port 104a of the feeding portion 104, the air in the tank is discharged through the breather tube 110, so that the gasoline supply is performed smoothly and air bubbles are prevented from being mixed with the gasoline in the tank.

The connecting method is shown in FIGS. 7 and 8.

The inlet pipe 102 provided with the flat attachment portion 102a, the flat support portion 102b and a hole 102c, the breather tube 110 (indicated by two-dotted chain lines in FIGS. 7 and 8) provided with a flared expanded portion 110b (flare angle 45) at the open end 110c, an approximately rectangular parallelepiped electrode 106, a ring electrode 107, and a support base 108 are prepared. One of the electrodes 106 and 107 is the anode and the other is the cathode.

Firstly, the approximately rectangular parallelepiped electrode 106 is inserted into the inlet pipe 102 from the side of the feeding portion 104. The electrode 106 is disposed so as to contact the whole inner surface of the flat attachment portion 102a. The flat support portion 102b of the inlet pipe 102 is disposed to abut the support base 108 in order to prevent the inlet pipe 102 from turning (around the axis). Then the ring electrode 107 is fitted around the breather tube 110 in the region adjacent to the expanded portion 110b. The inner diameter of the electrode 107 is approximately the same as the outer diameter of the breather tube 110.

Subsequently, the ring electrode 107 is arranged to face the electrode 106 within the inlet pipe 102 and moved downward (indicated by an outlined arrow in FIGS. 7 and 8) until the open end of the expanded portion 110b of the breather tube 110 contacts the flat attachment portion 102a of the inlet pipe 102. Then, while pressing the ring electrode 107 toward the electrode 106, an electric current is passed through both of the electrodes 106 and 107. As a result, while the end of the expanded portion 110b is welded to the flat attachment portion 102a by the resistance heat, the expanded portion is gradually spread by the pressure, and the spread portion is also welded. Thus, the expanded portion 110b finally becomes a flange 110a, the whole circumference of which is welded to the flat attachment portion 102a.

This producing method achieves the following results:

(1) The production costs can be reduced because a high temperature furnace as in a conventional method is no longer necessary.

(2) Forming the flared expanded portion 110b (flare angle 45) at the open end 110c of the breather tube 110 is easier than forming a flange 110a at the open end 110c of the breather tube 110 because the required rate of expansion is lower.

(3) During projection welding, pressure is imposed while the resistance heat is generated, and therefore the flared expanded portion 110b is easily spread to form a flange 110a while being projection welded.

(4) Since a flat surface is provided around the hole 102c, projection welding is easier compared with the case where welding is performed on a curved surface such as a cylindrical surface.

(5) Projection welding brings a smaller oxidized region compared with brazing because a thermally affected region is smaller. Additionally, since the material for the breather tube 110 and the inlet pipe 102 is SUS304, SUS304L or SUS436 according to JIS, oxidization is further suppressed and a high strength of connection can be maintained during a long-term use.

Next, a fuel inlet having a double structure in the vicinity of the fuel port is described.

A fuel inlet 201 shown in FIG. 9 comprises an inlet pipe 211, a retainer 213, a spiral groove 215, and the like.

The inlet pipe 211, which is formed by processing a metal pipe, is provided with an expanded portion 211a, a taper portion 211b and a main body 211c in the order from the fuel port side. The open end 211d of the inlet pipe 211 in the direction of the fuel port is flared and its edge plays the role of sealing the inside of the fuel inlet 201 by keeping close contact with a fuel cap 216. The not-shown rearward end of the inlet pipe 211 is connected to the connecting pipe J shown in FIG. 31, through which it is connected to a fuel tank T. In short, the inlet pipe 211 introduces fuel into the fuel tank T.

The retainer 213, which is formed by processing a metal pipe, has an outer circumference overlapping the inner circumference of the pipe 211. That is, the fuel inlet 201 in the vicinity of the fuel port has a double structure. One open end of the retainer 213 is positioned slightly backward from the flared open end 211d of the inlet pipe 211, and the other open end is narrowed to form an interference portion 213a. The interference portion 213a employed for a car running solely on lead-free gasoline is designed to allow the insertion of a fuel feeding nozzle for lead-free gasoline while rejecting the insertion of a fuel feeding nozzle for leaded gasoline. The retainer 213 also carries out the function of holding the fuel feeding nozzle for lead-free gasoline when it is inserted.

The spiral groove 215, a screw groove to which the fuel port cap 216 can be screwed, is formed when the inlet pipe 211 and the retainer 213 are crimped together. In other words, the inlet pipe 211 and the retainer 213 are crimped to be united when the spiral groove 215 is formed. The inlet pipe 211 and the retainer 213 may be further fixed with each other by welding or soldering in addition to the crimping, although fixing merely by the crimping is usually enough.

The method of producing the fuel inlet 201 is described with reference to FIG. 10.

Firstly, an inlet pipe 221 (a different number is given to differentiate this from a finished inlet pipe 211) is prepared. The inlet pipe 221 is provided with an expanded portion 221a, a taper portion 221b and a main body 221c formed by increasing the diameter of one end thereof by bulging, and the end of the expanded portion 221a is flared. Also prepared is a retainer 223 (a different number is given to differentiate this from a finished retainer 213). The retainer 223 is made of a metal pipe having an outer circumference fitting the inner circumference of the expanded portion 221a of the inlet pipe 221 when inserted into the expanded portion 221a. One end of the retainer 223 is narrowed to form an interference portion 223a.

After the retainer 223 is inserted into the expanded portion 221a of the inlet pipe 221, a core bar 232 fixed to a pipe end pressure die 231 is inserted into the retainer 223. The core bar 232 is provided with a recess 232a used to form the spiral groove 215. The other end of the retainer 223 is slightly separated from the open end of the inlet pipe 221 due to a step portion of the core bar 232. Then, while the expanded portion 221a, the taper portion 221b and the main body 221c of the inlet pipe 221 are securely held by a hydraulic clamp 230, the pipe end pressure die 231 and the hydraulic clamp 230 are pressured in the approaching directions with each other.

In the above state, a roller 240 is pressed on the outer circumference of the expanded portion 221a of the inlet pipe 221 while the roller 240 is rotated around the pipe axis C and at the same time gradually moved axially.

The roller 240 is rotatably held by a roller shaft 242 provided (approximately parallel to the pipe axis C) in a roller support 241. The roller support 241 is attached to an annular rotary body 245 rotatable around the pipe axis C such that the support 241 is movable by means of a hydraulic cylinder 243 in the radial direction of the rotary body 245 (in the direction indicated by the arrow in FIG. 10).

When the roller support 241 is moved radially inward by the hydraulic cylinder 243, the roller 240 is moved in the same direction, with the result that the roller 240 is pressed on the outer circumference of the inlet pipe 221. And when the rotary body 245 is gradually moved axially while rotating around the pipe axis C such that the roller 240 traces the recess 232a of the core bar 232, the roller 240 is also gradually moved axially rotating around the pipe axis C, while pressing on the overlapping portion of the inlet pipe 221 and the retainer 223.

Then the rotation of the rotary body 245 is stopped, the roller support 241 is moved radially outward by the hydraulic cylinder 243, and the core bar 232 is removed after the holding by the hydraulic clamp 230 is cancelled. Thus, the fuel inlet 201 shown in FIG. 9 is obtained.

According to the fuel inlet 201 described above, since a double structure in the vicinity of its fuel port is given by the retainer 213 and the spiral groove 215 to screw the fuel port cap 216 therein is provided within the double structure portion, durability against repeated opening/closing operations of the fuel port cap 216 as well as resistance to impact caused by an accident is good.

Additionally, since crimping the inlet pipe 211 and the retainer 213 together leads to their unity and simultaneous formation of the spiral groove 215, either welding and the like to unite the inlet pipe 211 and the retainer 213 or conventional complicated folding operation is not required. Thus, production of the present fuel inlet is remarkably easy.

Furthermore, since crimping and simultaneous formation of the spiral groove 215 in the fuel inlet 201 are carried out using the roller 240, a fuel inlet having the expanded portion 211a of a different diameter can be produced by simply replacing the core bar with another core bar corresponding to the diameter and using the same roller 240. Fuel inlets of various sizes thus can be produced easily.

Alternatively, crimping and simultaneous formation of the spiral groove 215 are carried out by a common pressing using, instead of the roller 240, a pair of metal die halves formed to have a configuration approximately corresponding to the core bar 232.

Also, a straight pipe without an interference portion may be used as the reinforcement housing.

Next, a fuel inlet provided with an integrated outer-cylinder-like flange in the expanded portion will be described.

As shown in FIG. 11, a fuel inlet 301 comprises an inlet pipe 311 and a retainer 313.

The inlet pipe 311 formed by processing a metal pipe is provided with a spiral groove 311a into which a screw-type fuel port cap C can be screwed in the vicinity of one open end, and an integral outer-cylinder-like flange 312 around the outer circumference in the vicinity of the open end. The flange 312 is formed by expanding, radially outward, the edge 311b on the side of the inlet pipe 311 where the fuel port cap C is screwed then by folding back in the axial direction. The free end 312a of the flange 312 extends beyond the position of the spiral groove 311a, and is separated from the outer circumference 311c of the inlet pipe 311. The flange 312 with an outer-cylinder-like configuration has an outer diameter larger than the outer diameter of the fuel port cap C. The fuel inlet 310 has a space 314 enclosed by the flange 312.

The retainer 313 formed by processing a metal pipe is fixed on the inner surface of the pipe 311 more backward than the spiral groove 311a by brazing or the like. The open end of the retainer 313 on the fuel tank T side is narrowed to form an interference portion 313a.

The process of fixing the fuel inlet 301 is described below. A car body B is provided with a fuel inlet supporting hole 315, which has a synthetic resin seal 315a attached along the inner circumference thereof. The edge 311b of the fuel inlet 301 is forced into the inside of the seal 315a of the fuel inlet supporting hole 315 until the edge 311b reaches a predetermined position. As a result, the fuel inlet 301 is fixed to the car body B with the flange 312 pressed by the fuel inlet supporting hole 315.

In this fixing structure, relative movement between the fuel inlet 301 and the car body B is possible. Therefore, even if a load in the direction indicated by the outlined arrow in FIG. 11 is imposed on the car body B in an accident, for example, the car body B becomes dented independently of the fuel inlet 301, which is therefore not directly affected by the load. If a load in the direction indicated by the black arrow in FIG. 11 is imposed on the car body B in an accident, the car body B bulges independently of the fuel inlet 301, which also is not directly affected by the load. In this case, there is no fear that the fuel port cap C comes off because of the bulging of the car body B since the outer diameter of the fuel port cap C is smaller than the outer diameter of the flange 312.

In the above described fuel inlet 301