Bent pipe and manufacturing method thereof

In a hose having a bent portion, a poor appearance part is prevented from being created in an inner round portion of the bent portion. A bent pipe has a bent portion located in an intermediate part in a longitudinal direction in which a cross section in a radial direction of a round of the bent portion is formed in a flat shape, and non-bent portions being continuous with the bent portion. The flat shape of the bent portion is a vertically long flat shape. With this configuration, when an unvulcanized hose is put on a mandrel and vulcanized, an inner round portion of the unvulcanized hose comes into tight contact with a bent portion of the mandrel and is not separated from the bent portion, so that the poor appearance part is hardly created in an inner round portion of the bent portion.

CROSS-REFERENCE TO RELATED APPLICATION AND TECHNICAL FIELD

The present application claims priority from Japanese Application No. 2014-102891, filed on May 16, 2014, the contents of which are hereby incorporated in full by reference.

The present invention relates to a bent pipe such as a radiator hose which has a bent portion in an intermediate portion in a longitudinal direction thereof and a manufacturing method of the bent pipe.

BACKGROUND ART

As a general model of a conventional bent pipe and a manufacturing method of the bent pipe, a rubber radiator hose which is formed in the shape of a bent pipe by a mandrel will be explained with reference toFIGS. 14 to 16.FIG. 14is a plan view of a hose110having an intermediate portion bent approximately 90°. This hose110is provided with a bent portion120in a middle portion thereof and straight portions130and132connected to each side of the bent portion120in the longitudinal direction thereof.

In this example, the bent portion120and the straight portions130,132are formed in a perfect circle shape in rotational cross section having an inner diameter D respectively as indicated by (a) and (b) in the drawing, and the bent portion120is formed in a curved round shape bent approximately 90°. In addition, a cross section indicated by (c) in the drawing corresponds to a cross section of a bent portion having a horizontally long elliptical shape (horizontally long flat shape), which is disclosed in a Patent Reference 1, discussed below.

Herein, various terminology used in this application will be explained. A circle having a curvature of a circular arc forming a round shape portion is a round circle C, a center of this round circle C is a round center CO, and a radius of the round circle C is a round radius CR. A numerical value of the round radius is a value of a round indicating a size of the round shape portion. For example, in the case where the round radius is 40 mm, a round of the round shape portion is 40 and is expressed as R40. It is noted that when the round radius CR is small, the curvature of the round shape portion is large, and the curvature of the round shape portion increases with decrease in the round radius CR.

Moreover, a center axis of the hose is HC, and a point on the center axis HC is a hose center HO. A cross section of the hose taken in an orthogonal direction of the center axis HC is a transverse cross section, in which a cross section of the bent portion taken in the radial direction of the round is a cross section in the radial direction of the round (the round radius direction).

Further, a condition of the hose shown from a direction orthogonal to the round circle C is a plan view. In this plan view, a side of the round center CO of the bent portion is an inside and an opposite side is an outside. An outer circumferential surface of the hole located between the inside and the outside is a lateral surface.

Furthermore, in the cross section in the radial direction of the round, the direction of the round radius is a vertical direction, and the direction orthogonal to the vertical direction is a horizontal direction. In a cross sectional shape in the radial direction of the round, a shape having different lengths in the vertical direction and in the horizontal direction passing the hose center HO is a flat shape. In particular, the shape of which the length in the horizontal direction is larger than that in the vertical direction is a horizontally long flat shape, while the shape of which the length in the vertical direction is larger than that in the horizontal direction is a vertically long flat shape.

Still further, a straight line passing the round center CO and the hose center HC is a center line L1in the vertical direction, and a straight line which is orthogonal to the center line L1in the vertical direction and passes the hose center HO is a center line L2in the horizontal direction (seeFIG. 2).

Like reference characters shall be commonly used in embodiments to referred to later.

In addition, in the description with reference to the drawings, the orientation such as upward, downward, left, right and the like shall be designated based on each direction such as upward, downward, left, right and the like in the drawings referred to in the description.

FIG. 15shows a cross section of the bent portion120at the time of finishing a vulcanizing molding. The hose110is formed in the same bent shape as a mandrel140by putting an unvulcanized hose on the mandrel140which has the same bent shape as the hose110, and vulcanizing it by heating it at a predetermined temperature.

At that time, a bent portion142of the mandrel140has substantially the same curvature as an inner circumferential portion of the bent portion120. In the case where a round of an inner round portion144of the bent portion142is sharp to some extent, an inner round portion124of the bent portion120is separated from the inner round portion144of the mandrel140when the unvulcanized hose is put on the mandrel140, and a space180is formed between the inner round portion124and the inner round portion144.

Then, since the inner round portion124is compressed toward the center in the longitudinal direction as indicated by an arrow f1, the inner round portion124is subjected to buckling deformation toward an inside of the space180by compression force in the direction of arrow f1. Due to this buckling deformation, a poor appearance part190formed in an irregular shape, such as wrinkles or the like, is easily produced.

The reason why the space180is formed is because the inner round portion124is subjected to a restoring force in the direction of arrow f3which is separated from the inner round portion144of the mandrel and directed to the round center CO, due to its own restoration elasticity by bending, and by this restoring force, the inner round portion124has a tendency to be separated apart from the inner round portion144of the mandrel. At that time, since the restoring force increases with a decrease in round of the inner round portion124, the space180is easy to be formed.

In addition, an outer round portion126of the bent portion120is pulled in the directions indicated by arrows f2and comes into tight contact with an outer round portion of the mandrel. Therefore, the poor appearance part190may not be formed, or only minimally formed, on the outside.

Further, there is another example in which, in order to suppress the creation of the poor appearance part190on the inside of the bent portion, the bent portion is formed in a horizontally long flat shape (seeFIG. 14(c)) and a circumferential length of an inner circumference of the hose is gradually increased (see the Patent Reference 1) in the longitudinal direction of the hose.

RELATED ART REFERENCE

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

As disclosed in Patent Reference 1, when the bent portion is formed in a horizontally long flat shape and the circumferential length is gradually increased, the inner round portion124is pulled in the circumferential direction and comes into tight contact with the inner round portion144of the mandrel, so that the creation of wrinkles or the like can be suppressed to some extent. However, even if the bent portion is formed in such horizontally long flat shape, there may be cases where the creation of the wrinkles or the like cannot be suppressed depending upon the size of the round in the inner round portion124.

FIG. 16shows diagrams explaining the fundamentals of molding for forming the bent portion into a horizontally long flat shape, in which (A) is a diagram placing an inner circumferential configuration170of the bent portion142of the mandrel corresponding to an outer circumference of a cross section of the bent portion142(FIG. 15) of the mandrel taken in the radial direction of the round on a reference inner circumferential circle160corresponding to the inner circumference of the unvulcanized hose of a perfect circle. The inner circumferential configuration170is a horizontally long flat shape.

When putting the unvulcanized hose on the bent portion142of the mandrel, each of end portions170ain the left and right direction of the inner circumferential configuration170of the bent portion expands the reference inner circumferential circle160in the left and right directions since the inner circumferential configuration170is of horizontally long flat shape. Therefore, left and right portions160aof the reference inner circumferential circle160are pulled toward the end portions170ain the left and right direction, and an upper portion160band a lower portion160care pressed against an upper portion170band a lower portion170cof the inner circumferential configuration170of the bent portion.

FIG. 16(B)shows a fitted condition of the unvulcanized hose. The reference inner circumferential circle160ofFIG. 16(A)is compressed as shown in a phantom line160A in the direction in which the upper portion160band the lower portion160capproach, so that it is formed into a horizontally long flat shape similar to the inner circumferential configuration170of the bent portion thereby to come into contact with the circumference of the inner circumferential configuration170, and the upper portion160band the lower portion160cof the reference inner circumferential circle160make tight contact with the upper portion170band the lower portion170cof the inner circumferential configuration170of the bent portion (the reference inner circumferential circle160A shown in the drawing is not placed on but slightly separated from the inner circumferential configuration170of the bent portion for the sake of explanation).

At that time, the upper portion160band the lower portion160care pulled toward the end portions170ain the left and right directions and pressed firmly against the upper portion170band the lower portion170cof the inner circumferential configuration170of the bent portion.

Since the lower portion160cof the reference inner circumferential circle160is merely pulled toward the left and right portions160ain the directions of arrows f4and pressed against the lower portion170cof the inner circumferential configuration170of the bent portion, it moves downwardly in the drawing as shown by arrow f3when some other force acts, and is deformed into such a shape as shown in a phantom line160B so as to be separated from the lower portion170cof the inner circumferential configuration170of the bent portion, so that the space180is formed between the lower portion160cand the lower portion170c. This force in the direction of arrow f3is the restoring force of the inner round portion124referred to above.

Then, when the inner round portion144of the mandrel is decreased in size so as to make the inner round portion124of the hose smaller than the predetermine limits, the restoring force of the inner round portion124of the hose is increased. This force acts in the direction of arrow f3ofFIG. 16(B)and prevails over the pulling force which presses the lower portion160cagainst the lower portion170c, so that the lower portion160cis separated from the lower portion170c.

Herein, the lower portion170cof the inner circumferential configuration170of the bent portion corresponds to the inner round portion144of the bent portion142of the mandrel. Moreover, the lower portion160cof the reference inner circumferential circle160corresponds to the inner round portion124of the bent portion120of the hose.

Accordingly, the inner round portion124of the hose is separated from the inner round portion144of the mandrel thereby to form the space180, so that the poor appearance part190is created. In addition, even if the cross section of the bent portion of the hose is formed in a horizontally long flat shape, the space180is inevitably formed when the round of the inner round portion124is decreased smaller than the predetermined limits.

Hitherto, the round of the predetermined limits in which the space180is created is about twice as large as an inner diameter D. When the round is less than twice of the inner diameter D, the space180is formed, and as a result, there is a possibility that the poor appearance part190is created. Therefore, the round must be increased more than twice of the inner diameter D.

However, if the round of the bent portion is larger, an arrangement space must become larger. Accordingly, it has been required that the round is decreased in size in order to realize a compact arrangement. Moreover, such requirement of the decrease in size of the round is increasing. For example, in the case of a radiator hose of a motor vehicle, it is required in order to have a radiator and surrounding component members of an engine arranged compactly within an engine room without interference between the radiator and the surrounding component members to realize a compactification of a vehicle body. Therefore, it is desired to provide the bent pipe such as a hose and the like having a small round bent portion of less than twice of an inner diameter which has not been realized so far without impairing an external appearance, and a manufacturing method thereof.

Further, in the case where the circumferential length of the inner circumference is gradually increased in the longitudinal direction, as disclosed in the Patent Reference 1, it is conceivable that the unvulcanized hose comes into tight contact with the mandrel to be able to decrease the size of the round to some extent. However, when changing the circumferential length in such a way, as described above, the diameter of the unvulcanized hose is gradually increased in the longitudinal direction, so that the thickness varies in the longitudinal direction. Therefore, since a change of strength in the longitudinal direction is increased, the durability may be deteriorated. Accordingly, it is also desired to realize the decrease in size of the round without changing the circumferential length in the longitudinal direction.

It is an object of the resent invention to realize the above discussed improvements.

Means for Solving the Problem

In order to achieve the above described object, according to a first feature of the present application, there is provided a bent pipe comprising a bent portion (20) located in an intermediate part in a longitudinal direction in which a cross section in a radial direction of a round of the bent portion (20) is formed in a flat shape, and non-bent portions (30,32) continuous with the bent portion (20), wherein the flat shape is a vertically long flat shape.

According to a second feature of the present application, in addition to the first feature, in a transverse cross section of the bent pipe, a circumferential length of the bent portion (20) is the same as each of circumferential lengths of the non-bent portions (30,32).

According to a third feature of the present application, in addition to the second feature, transverse cross sections of the non-bent portions (30,32) are formed in a perfect circle shape, and the pipe varies continuously in order of the non-bent portion (30), the bent portion (20) and the non-bent portion (32) in the longitudinal direction.

According to a fourth feature of the present application, in addition to any one of the first to third features, the bent portion (20) has a cross section of a vertically long elliptical shape or vertically long non-circular shape.

According to a fifth feature of the present application, in addition to any one of the first to fourth features, a cross sectional shape in the radial direction of the round of the bent portion (20) is asymmetric in a vertical direction.

According to a sixth feature of the present application, in addition to any one of the first to fifth features, the cross sectional shape in the radial direction of the round of the bent portion (20) is asymmetric in a horizontal direction.

According to a seventh feature of the present application, in addition to any one of the first to sixth features, each of the non-bent portions (30,32) has a cross sectional part of perfect circle shape, and an inner round (24) of the bent portion (20) is less than twice of an inner diameter D of the cross sectional part of perfect circle shape.

According to an eighth feature of the present application, there is provided a manufacturing method of a bent pipe in which an unvulcanized pipe (50) is put on a mandrel (40) having a mandrel bent portion (42) in an intermediate part in a longitudinal direction and vulcanized so as to be molded in a bent pipe shape similar to a shape of the mandrel, wherein the mandrel bent portion (42) has a vertically long shape in cross section in the radial direction of a round thereof.

Effects of the Invention

According to the first feature of the present application, since the cross sectional shape in the radial direction of the round of the bent portion is the vertically long flat shape, creation of a poor appearance part, such as wrinkles or the like, is in an inside of the bent portion is minimized or eliminated, even if the round on the inside of the bent portion is smaller than predetermined limits.

According to the second feature of the present application, since in a transverse cross section of the bent pipe, the circumferential length of the bent portion is the same as each of the circumferential lengths of the non-bent portions, a thickness in the longitudinal direction is made uniform so as to be able to make strength in the longitudinal direction constant.

According to the third feature of the present application, the transverse cross sections of the non-bent portions are formed in a perfect circle shape, and the pipe varies continuously in order of the non-bent portion (30), the bent portion (20) and the non-bent portion (32) in the longitudinal direction, so that only the bent portion has the transverse cross section of vertically long flat shape and other portions have the cross section of perfect circle shape. Therefore, it is possible to prevent the creation of the poor appearance part, such as the wrinkles or the like.

According to the fourth feature of the present application, since the bent portion has a cross section of vertically long elliptical shape or vertically long non-circular shape, the degree of freedom in designing the cross sectional shape of the bent portion is increased.

According to the fifth feature of the present application, since an inside or outside of the bent portion is partially deformed so as to make the cross sectional shape asymmetric in the vertical direction, a clearance relative to surrounding component members may be provided, and the degree of freedom in designing the cross sectional shape of the bent portion is increased.

According to the sixth feature of the present application, since a lateral surface of the bent portion is deformed so as to make the cross sectional shape asymmetric in the horizontal direction, the clearance relative to surrounding component members may be provided, and the degree of freedom in designing the cross sectional shape of the bent portion is increased.

According to the seventh feature of the present application, even if the inner round of the bent portion is less than twice the inner diameter D of the non-bent portion of the bent pipe, the creation of the poor appearance part on the inside of the bent portion can be prevented. Therefore, it is possible to realize the small round of less than twice of the non-bent portion of the bent pipe, which has not been realized so far.

According to the eighth feature of the present application, the mandrel bent portion has a vertically long shape in cross section in the radial direction of the round thereof. Therefore, when the unvulcanized pipe is put on the mandrel and is bent, it is possible to bend the unvulcanized pipe without buckling deformation. Thus, the hose having the smaller round on the inside of the bent portion than the predetermined limits can be molded while suppressing the creation of the poor appearance part on the inside of the bent portion.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention embodied in a radiator hose for a motor vehicle will be explained with reference to the drawings.

FIGS. 1 through 9are views in accordance with the first embodiment, in whichFIG. 1is a plan view of a hose10,FIG. 2is a cross sectional view taken on line2-2ofFIG. 1, andFIG. 3is a cross sectional view taken on line3-3ofFIG. 1.

In these drawings, the hose10is a rubber hose which is vulcanized and molded of a proper rubber material, and has a bent portion20bent approximately 90° in an intermediate portion thereof. A first straight portion30and a second straight portion32of a straight pipe shape forming non-bent portions are formed on both sides in the longitudinal direction of the bent portion20. For convenience′ sake, an end in the longitudinal direction on the side of the second straight portion32is designated as a starting end34, and an end in the longitudinal direction on the first straight portion30is designated as a terminal end36.

The hose10is integrally molded with a reinforcing fabric12in an interior of a thickness thereof (seeFIGS. 2 and 3). The reinforcing fabric12is provided continuously over the whole length of the hose10. The reinforcing fabric12may be omitted while remaining within the scope of the instant disclosure.

The hose10is formed continuously from the first straight portion30through the bent portion20to the second straight portion32. Shapes in transverse cross section of the first straight portion30, the bent portion20and the second straight portion32are indicated as (a), (b) and (c) in the drawing. The shapes in transverse cross section vary at each position of round stops14.

A bent portion inside22and a bent portion outside23of the bent portion20are of round shape, respectively. An inner round portion24in an outer circumferential surface of the bent portion inside22is of circular arc of a round circle C, and a round radius of this round circle C is CR. Namely, the round of the inner round portion24is CR (a numerical value). Herein, the round is set to a value less than twice of an inner diameter D. For example, D=30 mm, CR=40 mm, and the round of the inner round portion24is R40. This round corresponds to about 4/3D, so that it is remarkably small in the hose of this size. In addition, an inner circumferential round25of the bent portion inside22is larger by an amount equal to its thickness.

An outer round portion26which is a round portion of an outer circumference of the bent portion outside23of the bent portion20is larger than the round of the inner round portion24substantially by an amount equal to an outer diameter (long diameter) in a vertically long direction of the bent portion. An inner circumferential round27of the bent portion outside23is smaller than the outer round portion26by an amount equal to its thickness.

A cross section (transverse cross section) in the radial direction of the round of the bent portion20, as shown inFIG. 2, is formed in a vertically long elliptical shape in the radial direction of the round circle C. An elliptical shape on an inner circumferential side of the vertically long elliptical shape is a vertically long flat shape which projects in the vertical direction and has a long radius a in the vertical direction and a short radius b in the horizontal direction.

The long radius a extends in a superposed relation with a vertically extending center line L1which connects a hose center HO and a round center CO. The short radius b extends in a superposed relation with a horizontally extending center line L2which intersects at right angles with the vertically extending center line L1and passes through the hose center HO. Letting the inner diameter of the first straight portion30(the second straight portion32) be D, and the radius be r, a>r>b. Letting an amount of vertical projection be d, d=a−r.

In addition, since the thickness is constant, an outer circumferential side of the vertically elliptical shape has a vertically long elliptical shape similar to the inner circumferential side thereof.

A cross section of the first straight portion30is of perfect circular shape as shown inFIG. 3, and an inner diameter thereof is D. The second straight portion32on an opposite side of the bent portion20has the same inner diameter as the first straight portion30. Namely, the hose10is of perfect circular cross section of the same inner diameter over the whole length thereof excluding the bent portion20.

Straight lines L3and L4are two orthogonal axes passing through the center HO and each corresponding to L1and L2ofFIG. 2. L3is a vertically extending center line in the upward and downward direction of the drawing, and the L4is a horizontally extending center line in the left and right direction of the drawing.

A circumferential length of an inner circumference of each of the bent portion20, the first straight portion30and the second straight portion32is L, and it is the same including portions of the round stops14. Namely, each of the inner circumferential lengths of the cross section (FIG. 2) in the radial direction of the round (hereinafter, to be referred also to the round radius direction) of the bent portion20and the transverse cross section (FIG. 3) of the first straight portion30(the second straight portion32) is the inner circumferential length L. Herein, although inFIGS. 2 and 3, the reference character L points to an inner circumferential surface of the hose, L references the circumferential length. The expression with respect to the circumferential length L in cross section is the same in other drawings. In addition, in this embodiment, since the thickness of the hose10is substantially constant over its whole length, the circumferential length of each of the portions is the same in outer circumferential length.

Further, although the shape in transverse cross section of the hose10varies at the round stops14from a perfect circle to an ellipse or an ellipse to a perfect circle, this variation in cross sectional shape is made gradually in such a manner that the bent portion20is smoothly connected to each of the first straight portion30and the second straight portion32located on both side thereof. The circumferential length L is also kept identical in this variation part. Accordingly, a passage cross sectional area of the hose10is constant over the whole length thereof.

Next, a manufacturing method of this hose10will be explained.

As shown inFIG. 4, an unvulcanized hose50(corresponding to an unvulcanized pipe in this application) of perfect circular cross section which is unvulcanized is put on a mandrel40of bent pipe shape, and then the unvulcanized hose50is heated at a predetermined temperature in a condition where the unvulcanized hose50is bent along the bent shape of the mandrel40, so that the unvulcanized hose50is vulcanized and molded into the hose of bent pipe shape which is fixed in the same shape as the mandrel40.

The mandrel40is made of a metallic round bar and formed with a mandrel bent portion42of which an intermediate portion in the longitudinal direction is bent approximately 90°. Reference characters43designate round stops. The mandrel40varies in cross section in order of a perfect circle, a vertically long ellipse and a perfect circle in the longitudinal direction, with the round stops43serving as a boundaries.

A mandrel inner round portion44of the mandrel bent portion42has a round shape substantially the same as the inner circumferential round25(FIG. 1) of the bent portion inside22of the bent portion20of the hose10. Moreover, a mandrel outer round portion46of the mandrel bent portion42also has a round shape substantially the same as the inner circumferential round27(FIG. 1) of the bent portion outside23of the bent portion20of the hose10.

Since the mandrel40molds the hose10in a condition where the hose10is fitted coaxially to the mandrel40from outside, as described below, like elements of the mandrel40are given like reference characters of the hose10, such as HC, HO, a, b, r, CO, L1, L2, L3and L4. In addition, since a round circle of the mandrel corresponds to the inner circumferential round25, it is designated Ca in distinction from the round circle of the inner round portion24, and a radius of the round of the round circle of the mandrel is designated CRa.

On one end side in the longitudinal direction of the mandrel bent portion42there is formed a mandrel first straight portion47an end47aof which is formed in a curved surface shape in order to make it easy to insert the unvulcanized hose50. A mandrel second straight portion48is formed on the opposite side of the mandrel first straight portion47. A mounting portion49is provided on an end portion of the mandrel second straight portion48in a projecting fashion. When the mounting portion49is mounted on a frame member (not shown), the mandrel40is carried on the frame member.

As shown inFIG. 5, a transverse cross section of the mandrel bent portion42is of vertically long elliptical shape, and an outer circumference of the mandrel bent portion42corresponds with the inner circumference of the bent portion20. Namely, a circumferential length of a cross section in the round radius direction of the mandrel bent portion42is L.

The mandrel inner round portion44and the mandrel outer round portion46protrude inwardly and outwardly as much as d with respect to a concentric circle of a radius r, respectively. The circle of the radius r is a circle of an outer circumference in transverse cross section of each of the mandrel first straight portion47and the mandrel second straight portion48. This radius r is also an inner diameter of each of the first straight portion30and the second straight portion32.

The cross sections of the mandrel first straight portion47and the mandrel second straight portion48are formed in the shape of a perfect circle, respectively, as shown inFIG. 6, of which an outer circumference corresponds to an inner circumference of each of the first straight portion30and the second straight portion32. Namely, the outer diameter is D, and the radius is r. In addition, althoughFIG. 6shows a cross section of the mandrel first straight portion47, the mandrel second straight portion48also has the same cross section.

Moreover, circumferential lengths of the outer circumferences of each of the mandrel bent portion42, the mandrel first straight portion47and the mandrel second straight portion48are identical with each other and correspond with the circumferential length L of the inner circumference of the hose10.

FIG. 7shows a condition where the unvulcanized hose50is put on the mandrel40. As shown inFIG. 7, one end portion59aof the unvulcanized hose50is put on a tip47aand forced forward, so that the mandrel40is inserted into the inside of the unvulcanized hose40. Then, the unvulcanized hose50is bent along the mandrel bent portion42, and an unvulcanized hose bent portion52is formed in an intermediate portion in the longitudinal direction of the unvulcanized hose50. Both sides in the longitudinal direction of the unvulcanized hose bent portion52extend along the mandrel first straight portion47and the mandrel second straight portion48so as to form an unvulcanized hose first straight portion57and an unvulcanized hose second straight portion58. The other end portion59bwhich is an end portion of the unvulcanized hose first straight portion57is located in the vicinity of the tip47a.

A transverse cross section of the unvulcanized hose bent portion52, as shown in a rotational cross section (a), is formed in a vertically long elliptical shape. An unvulcanized hose inner round portion54and an unvulcanized hose outer round portion56each make tight contact with the mandrel inner round portion44and the mandrel outer round portion46.

In particular, since the mandrel inner round portion44of the mandrel bent portion42protrudes in the direction of the round center CO, the unvulcanized hose inner round portion54is tightened by pressing the mandrel inner round portion44to come into tight contact with the mandrel inner round portion44firmly, and this tight contact is maintained.

A transverse cross section of the unvulcanized hose first straight portion57, as shown in a rotational cross section (b), is formed in a perfect circular shape and comes into tight contact with an outer circumference of the mandrel first straight portion47. Similarly, the unvulcanized hose second straight portion58is formed in a perfect circular shape and comes into tight contact with an outer circumference of the mandrel second straight portion48.

In this condition, when the unvulcanized hose50is heated, the unvulcanized hose bent portion52, the unvulcanized hose first straight portion57and the unvulcanized hose second straight portion58are vulcanized in a condition where they are in tight contact with the mandrel bent portion4, the mandrel first straight portion47and the mandrel second straight portion48, respectively. Thus, the unvulcanized hose bent portion52is molded into the bent portion20of the hose10. The unvulcanized hose first straight portion57is molded into the first straight portion30, and the unvulcanized hose second straight portion58is molded into the second straight portion32.

Further, the unvulcanized hose inner round portion54and the unvulcanized hose outer round portion56are molded into the inner round portion24and the outer round portion26, respectively. Moreover, a part of the unvulcanized hose50which contacts the mandrel inner round portion44is molded into the inner round25, and a part of the unvulcanized hose50which contacts the mandrel outer round portion46is molded into the inner round27. In addition, the one end portion59ais molded into the starting end34and the other end portion59bis molded into the terminal end36. In the drawing, the reference characters of each part of the hose20corresponding to each part of the unvulcanized hose50are given in parentheses.

After being vulcanized, the inner circumferential round25of the bent portion inside22of the hose20is formed in a tight contact condition along the mandrel inner round portion44, and the inner round portion24is formed with a predetermined small round (less than 2D, for example R40 or so). As a result, it is possible to obtain the hose10which does not have a poor appearance part, such as wrinkles or the like in the bent portion inside22.

In addition, the inner circumferential round27of the bent portion outside23is formed along the mandrel round portion46of the mandrel bent portion42, and the outer round portion26is formed with a predetermined round.

Further, since the circumferential length of the outer circumference of the mandrel40over the whole length in the longitudinal direction of the mandrel is identical with L, the circumferential length of the inner circumference of the hose10is identical with L, so that the inner circumferential length of each of the bent portion20, the first straight portion30and the second straight portion32is L.

Next, the fundamentals of molding for forming the bent portion will be explained with reference toFIG. 8. In this diagram, similarly toFIG. 16(A), a bent portion inner circumferential configuration70is placed on a reference inner circumferential circle60.

The reference inner circumferential circle60shows the outer circumference of perfect circular shape in cross section of each of the mandrel first straight portion47and the mandrel second straight portion48and has a radius r.

The bent portion inner circumferential configuration70schematically shows the outer circumference in cross section in the round radius direction of the mandrel bent portion42which has a vertically long non-circular shape consisting of an elliptical shape, and is formed in a vertically long elliptical shape which has a long radius a extending along the center line L1in the vertical direction and a short radius b extending along the center line L2in the horizontal direction. The circumferential lengths of the reference inner circumferential circle60and the bent portion inner circumferential configuration70are shown as (L) and are identical with each other.

When intersecting points between the bent portion inner circumferential configuration70and the vertical center line L1are designated as an inward projection72and an outward projection74, and intersecting points between the reference inner circumferential circle60and the vertical center line L1are designated as an inner end portion44aand an outer end portion46a, the inward projection72projects inwardly from the inner end portion44aof the reference inner circumferential circle60(a projecting amount=d). Moreover, the outward projection74project outwardly from the outer end portion46aof the reference inner circumferential circle60by d.

Each of the inward projection72and the outward projection74has a length corresponding to the long radius a from the hose center HO. Since the inward projection72is a point located on the mandrel inner round portion44and overlaps with the unvulcanized hose inner round portion54, a reference character (54) is given in the drawing. Similarly, since the outward projection74is a point located on the mandrel outer round portion46and overlaps with the unvulcanized hose outer round portion56, a reference character (54) is given in the drawing.

When putting the unvulcanized hose50on the mandrel40, the unvulcanized hose bent portion52is deformed so as to become the same shape as the bent portion inner circumferential configuration70. At that time, due to the inward projection72and the outward projection74, the unvulcanized hose inner round portion54and the unvulcanized hose outer round portion56are extruded inwardly and outwardly by the length d from the inner end portion44aand the outer end portion46aof the reference inner circumferential circle60, respectively. Therefore, the unvulcanized hose inner round portion54and the unvulcanized hose outer round portion56each are brought into tight contact with the mandrel inner round portion44and the mandrel outer round portion46firmly.

In this condition, since the unvulcanized hose inner round portion54is extruded inwardly (In the direction of the round center CO) and pulled actively by the mandrel round portion44which projects inwardly of the mandrel, it is pressed firmly against the mandrel inner round portion44due to its elasticity so as to maintain the tight contact state, so that it is not separated from the mandrel inner round portion44even by the restoring force of the unvulcanized hose inner round portion54.

Accordingly, since a space (see the reference character180ofFIG. 15) is not formed between the unvulcanized hose round portion54and the mandrel inner round portion44, buckling deformation or the like does not occur in the unvulcanized hose round portion54. In addition, since the unvulcanized hose is vulcanized in this tight contact state, the poor appearance part is not created.

In addition, since this tight contact state is maintained even if the round of the mandrel inner round portion44is small, a small round (less than twice of the inner diameter D) which is smaller than 2D of the limits in the past, that is, such a small round as R40 in the case of D=30 mm can be realized.

Further, since the unvulcanized hose outer round portion56is brought into tight contact with the mandrel outer round portion46in substance by tension of a material itself at the time of fitting even if there is not provided a protruding portion such as the outward projection74, it is a part in which the wrinkles or the like is hardly created. However, when the mandrel outer round portion46is protruded outwardly as much as the length d, the unvulcanized hose outer round portion56makes tight contact with the mandrel outer round portion46more firmly, whereby the creation of the wrinkles or the like is prevented more accurately.

Further, since the reference inner circumferential circle60and the bent portion inner circumferential configuration70are the same in circumferential length, left and right parts of the bent portion inner circumferential configuration70located on intersecting points with the horizontal center line L2are pulled in the direction of the center HO when the unvulcanized hose inner round portion54and the unvulcanized hose outer round portion56are extruded inwardly and outwardly and extended in the vertical direction. Therefore, since lateral surfaces of the unvulcanized hose bent portion52come into tight contact with the intersecting points between the bent portion inner circumferential configuration70and the horizontal center line L2and with lateral surfaces of the mandrel bent portion42located in the vicinity of the intersecting points, the creation of the wrinkles or the like is prevented also in the lateral surfaces of the hose bent portion20.

According to the hose and the manufacturing method thereof in this embodiment, it is possible to realize the small round (less than twice of the inner diameter D, which was the past limit) while suppressing the creation of the poor appearance part. Therefore, the hose can be arranged compactly within the engine room, and the engine room can be compactified while making it possible to simplify a layout of the radiator and surrounding component members. In particular, when such small round as R40 in the case of D-30 mm is realized, the engine room can be compactified as much as possible.

Further, since the cross sectional shape in the round radius direction of the bent portion20is the vertically long elliptical shape or other vertically long non circular shape, the bent portion20can be formed in various vertically long non-circular shapes while taking the surrounding component members or the like into consideration, whereby the degree of freedom in designing the cross sectional shape of the bent portion20is increased.

Further, with respect to the cross sectional shape of the hose10, the first straight portion30and the second straight portion32forming non-circular portions are formed in a perfect circular shape. The first straight portion30of perfect circular shape in cross section, the bent portion20of vertically long elliptical shape in cross section and the second straight portion32of perfect circular shape in cross section are continuously connected in that order in the longitudinal direction while varying in shape. Therefore, since only the transverse cross section of the bent portion20is formed in a vertically long flat shape, and other portions are formed in a simple perfect circular shape, the whole can be formed in a simple shape.

Further, since each of the inner circumferential lengths of the bent portion20, the first straight portion30and the second straight portion32is identical with L, they do not become partially thin even if the bent portion20is pulled inwardly and outwardly, so that the thickness is maintained uniform over the whole length in the longitudinal direction. Therefore, the bent portion20does not decrease in strength, thereby increasing the durability thereof.

Further, since the cross section in the round radius direction of the bent portion20is formed in a vertically long elliptical shape as a vertically long flat shape, the circumferential length can be maintained uniform without increase in circumferential length in the longitudinal direction. Therefore, the creation of the poor appearance part can be suppressed, and the durability can be improved. Moreover, since the circumferential length including that of the bent portion20is constant in the longitudinal direction, the insertion and fitting between the mandrel and the hose each having a bent shape can be easily done, whereby it is possible to improve workability. In addition, the variation in passage cross section area in the bent portion20is suppressed, thereby obtaining the hose which is suitable for use as the hose for high pressure fluid and the like.

Referring to the hose disclosed in the Patent Reference 1, in the case where the bent portion is formed in a horizontally long flat shape and the circumferential length of the inner circumference is gradually increased in the longitudinal direction, the diameter of the unvulcanized hose is gradually increased in the longitudinal direction, so that the thickness varies in the longitudinal direction and durability is easily deteriorated. Therefore, even if the bent portion is formed with a small round to some extent while suppressing the creation of the poor appearance part, the durability may be deteriorated. In addition, since the passage cross section area varies in the longitudinal direction, the changes in fluid speed and pressure are developed, thereby the hose may not be suitable for use as a fluid hose.

FIG. 9is a view showing a modified example in a manner similar to that ofFIG. 8, in which a flattening rate is slightly changed. The flattening rate is increased by making the long radius a larger and the short radius b smaller. With this configuration, it is possible to obtain the similar effects of the vertically long elliptical shape. The extrusion by the mandrel inner round portion44is increased at the time of vulcanization, so that the inner round portion24is brought into tight contact with the mandrel inner round portion44more firmly. Therefore, it is possible to make the inner round portion24smaller in round size.

As the circumferential length is identical, the flattening rate can be set freely. When the flattening rate is large, the thickness in the left and right direction can be thinned. Therefore, an arrangement space in the left and right direction can be easily ensured in mutual relationship with the surrounding component members, whereby it is possible to increase the degree of freedom in layout.

Further,FIGS. 9 and 10show examples which are formed symmetric both in the left and right direction of the vertical center line L1(the left and right direction of the drawing) and in the inward and outward direction of the horizontal center line L2(the upward and downward direction of the drawing). This configuration also applies toFIG. 12.

In addition, it is possible to employ various vertically long flat shapes of non-circle in the cross section in the round radius direction of the bent portion20. Hereunder, this will be explained by an inner circumferential shape of the bent portion. In the following examples, the reference inner circumferential circle60, the vertical center line L1and the horizontal center line L2are identical with those ofFIGS. 8 and 9.

FIG. 10is a second embodiment showing an example in which the bent portion inner circumferential configuration replaces the bent portion inner circumferential configuration70with a vertically long oblong configuration70A. A reference character a designates a length between the center HO and each of an inward projection72A and an outward projection74A on the vertical center line L1, and b designates a length from the center HO to each of left and right sides on the horizontal center line L2. These lengths correspond to the long radius a and the short radius b of the bent portion inner circumferential configuration70, with the length a>the length b.

With this configuration, as the length a is larger than the radius r of the reference inner circumferential circle60, similar effects (such as suppression of creation of wrinkles or the like) can be expected. In addition, by employing the vertically long oblong configuration, the length a can be easily made longer. Moreover, since the bent portion outer circumference of the mandrel corresponds to the vertically long oblong configuration70A, and the inner circumference of the unvulcanized hose corresponds to the reference inner circumferential circle60, a contact region is decreased when the unvulcanized hose is fitted onto the mandrel, so that the resistance is decreased, thereby making it possible to improve workability.

The bent portion20and portions other than the bent portion have the same circumferential length (this applies to each example to be referred to below). The condition of a>r is sufficient if it is satisfied at least on the inward projection72side.

FIG. 11is a third embodiment showing an example in which the bent portion inner circumferential configuration is a triangle.FIG. 11(A)is an example in which a bent portion inner circumferential configuration70B is formed in an inverted triangle consisting of an isosceles triangle which has three sides (71a,71b,71c) and three apexes (73a,73b,73c). One apex73aprojects inwardly (downwardly in the drawing) from the center HO on the vertical center line L1, and other two apexes73b,73care spaced apart from the vertical center line L1in the left right directions and arranged above the center HO on the outside of the reference inner circumferential circle60. Each of the apexes is located on the outside of the reference inner circumferential circle60. The apex73aforms an inward projection72B. Outer projections74B are formed of the apexes73b,73cwhich form both ends of a horizontal base71a. With this configuration, the contact with the unvulcanized hose50is made at three points consisting of the three apexes (73a,73b,73c), whereby the fitting operation can be performed easily.

FIG. 11(B)shows an example in which a bent portion inner circumferential configuration70B is formed in an inverted triangle similar toFIG. 11(A), and a base71ais formed in a round shape. In this example, since an outward projection74B is located in a middle portion of the base71a, the whole base71ais able to make contact with a part corresponding to the unvulcanized hose outer round portion56(seeFIG. 7), so that it is possible to suppress the local deformation of the unvulcanized hose outer round portion56which is subjected to strong pulling force.

The examples inFIG. 11are formed asymmetric in the inward and outward directions (the vertical direction) with respect to the horizontal center line L2and symmetric in the left and right directions of the vertical center line L1.

When a cross section in the round radius direction of the bent portion is formed asymmetric in the vertical direction, the deformation region such as a clearance with respect to the surrounding component members or the like can be provided, whereby the degree of freedom in designing the cross sectional shape of the bent portion is improved.

FIG. 12is a fourth embodiment showing examples in which the bent portion inner circumferential configuration is formed in a polygon equal to or more than a tetragon.FIG. 12(A) shows an example having a bent portion inner circumferential configuration70C of vertically long substantially rectangular shape. The bent portion inner circumferential configuration70C has four sides (75a,75b,75c,75d) and four apexes (75e,75f,75g,75h). The upper side75aand the lower side75cextend horizontally, and the left and right sides75band75dare arranged in the upward and downward direction of the drawing respectively and extend in parallel with each other.

Inner projections72C are formed as the left and right apexes75f,75gon the lower side75a, and outer projections74C are formed as the left and right apexes75e,75hon the upper side75a.

With this configuration, the contact with the unvulcanized hose50can be made at four points, whereby a contacting region with the unvulcanized hose can be reduced. Herein, in the case where the bent portion inner circumferential configuration70C is formed in a tetragon, it is not limited to a rectangle and it may be formed in an inverted trapezoid which has the shorter lower side75cthan the upper side75a.

FIG. 12(B) is an example having a bent portion inner circumferential configuration70D of hexagon which has six sides (77a,77b,77c,77d,77e,77f) and six apexes (78a,78b,78c,78d,78e,78f). Short upper side77aand lower side77dare arranged horizontally. A pair of opposed left and right long sides77b, and77fextends downwardly and is inclined in an outwardly opening fashion on the upper side of the center HO. A pair of opposed left and right long sides77cand77eextends upwardly and is inclined in an outwardly opening fashion on the lower side of the center HO. The apex78bat which the sides77band77care connected to each other and the apex78eat which the sides77fand77eare connected to each other are arranged on the left and right sides of the vertical center line L1on the horizontal center line L1, respectively.

With this configuration, the contact with the unvulcanized hose50can be made at six points. Moreover, an essential part for molding the bent portion can be supported at four points on an inward projection72D comprised of relatively adjacent two apexes78cand78dand on an outward projection74D comprised of relatively adjacent two apexes78aand78fin a similar way.

FIG. 12(C)is an example having a bent portion inner circumferential configuration70E of hexagon similar to the bent portion inner circumferential configuration70D. However, all of the apexes are located outwardly of the reference inner circumferential circle60. An inward projection72E is comprised of one apex78d, and an outward projection74E is comprised of opposed one apex78a. In addition, upper sides77a,77fand lower sides77c,77dare inclined, respectively.

With this configuration, the contact with the unvulcanized hose50is made at six points by each of the six apexes. However, since an essential part for molding the bent portion are formed with the inward projection72E comprised of one apex78dand the outward projection74E comprised of similar one apex78a, the projection in the round radius direction is increased, thereby reducing the creation of the wrinkles or the like.

The bent portion inner circumferential configuration of polygon is not limited to the above referred examples. A pentagon, a heptagon or more polygonal shape may be employed.

FIG. 13is a fifth embodiment showing an example in which a bent portion inner circumferential configuration70F has a vertically long non-circular shape which is asymmetric and indeterminate both in the upward and downward direction and in the left and right direction of the drawing.

In this example, an inward projection72F extends downwardly of the reference inner circumferential circle60. An outward projection74F is an apex portion of a circular arc-shaped part79a. A left side portion which connects the circular arc-shaped part and the inward projection72F is comprised of a straight line part79band a round part79c, and a right side portion is comprised of a straight line part79d.

The inward projection72F and the outward projection74F are arranged asymmetric in the upward and downward direction of the drawing and are shifted from each other in the left and right directions.

With this configuration, the creation of the wrinkles or the like can be prevented by the inward projection72F. However, it is preferable that the inward projection72F approaches as close to the vertical center line L1in the radial direction of the round circle as possible. In addition, although the bent portion inner circumferential configuration70F is able to be formed in any indeterminate shape, it is preferable that a shape of each of the left side (79b,79c), the right side (79d) and the circular arc-shaped part79ais a straight line shape or a curved shape which is convexed outwardly in the radial direction of the reference inner circumferential circle60so as not to be concaved inwardly in the radial direction.

Further, since a cross sectional shape in the round radius direction is asymmetric in the horizontal direction, lateral surfaces of the bent portion are changed in shape so as to make it possible to provide a clearance or the like with respect to the surrounding component members, so that the degree of freedom in designing the cross sectional shape of the bent portion is improved. If it is asymmetric in each of vertical direction and the horizontal direction, the degree of freedom is increased further.

The cross sectional shape of the bent portion in the present application is sufficient if it is formed in a vertically long non-circular shape. As the vertically long non-circular shape, an elliptical circle (FIGS. 8 and 9), an oblong circle (FIG. 10), a polygonal shape (FIGS. 11 and 12) and an indeterminate shape as shown inFIG. 13may be employed. In addition, the bent portion is sufficient if at least an inside part projects in the round radius direction like the inward projection72ofFIG. 8, a length from the center HO is longer than the radius r of the reference inner circumferential circle60and there is a part which protrudes inwardly by d from the reference inner circumferential circle60. Therefore, various shapes may be employed other than the above described embodiments. The outward projection74(74A,74B,74C,74D,74E,74F) may be located in the reference inner circumferential circle60.

In addition, the cross sectional shapes in the first straight portion30and the second straight portion32are not limited to a perfect circle, and various non-circular shapes may be employed.

Further, the bent pipe includes a hose and tubular members such as a thinner tube or the like, and the range of its use is not limited to the radiator hose, but is applicable to various fluid pipes or tubes.

DESCRIPTION OF REFERENCE CHARACTERS