The present invention relates to a tube clamping structure in which a tube and a tubular opposing member such as a rigid pipe made, for instance, of resin, metal, etc. are connected in a fluid-tight condition. Such a structure is favorably used for clamping structures between tubes and metallic pipes for use in automobiles calling for resistance to gasoline.
A conventionally known clamping structure of this type is disclosed in Japanese Patent Unexamined Publication No. 4-171391 (1992). More particularly, this is a clamping structure as illustrated in FIG. 10 between a thin wall tube 7 and a metallic tube 5 arranged in the following manner: a connecting portion of the thin wall tube 7 is fitted to an outer periphery portion of a connecting portion of the metallic tube 5; a protecting sleeve 6, which is made of the same material as the thin wall tube 7, is fitted to an outer periphery portion of the connecting portion of the thin wall tube 7; and the outer periphery portion of the connecting portion of the protecting sleeve 6 is swaged by a metallic sleeve 8 at least at two spots that are located remote from each other. The structure is further arranged in that at least one groove 5a is provided on the outer periphery portion of the metallic tube 5, the groove 5a being located on either one of the at least two swaging portions and assuming a dimension such that its depth dimension is smaller than half a thickness of the thin wall tube and its width dimension is smaller than a width dimension of the swaging portion located at one spot of the metallic sleeve 8.
However, since relatively hard resin was employed for the thin wall tube 7, drawbacks were presented in that sealing properties between an inner peripheral surface of the tube and an outer peripheral surface of the metallic tubes 5 were inferior. While structures are accordingly employed for strongly swaging the sleeve from the outer periphery in order to improve sealing properties, it is difficult to employ such structures in assembly worksites for automobiles or the like, since such swaging operations need to be performed by using a swaging device. Problems of leakage of fluid were also presented that were due to creases generated in the course of swaging.
The present invention has been made in view of these circumstances, and it is a first object of the present invention to provide a tube connecting structure capable of easily improving sealing properties between tubes and tubular opposing members in addition to enabling easy connection at any spot, e.g. assembly worksites for automobiles. It is another object of the present invention to provide a tube connecting structure for preventing leakage of fluid owing to creases generated in the course of swaging.
For achieving the above objects, the present invention provides a tube clamping structure for connecting an opposing member to one end of a tube comprising:
a tube extending from one end to another end; an engaging end portion being formed at one end of the tube and extending in an axial direction, and including an annular concave portion that is formed at an inner peripheral surface thereof and that is located to be remote from an one end surface in the axial direction; a tubular elastic sealing member inserted and attached to the engaging end potion of the tube; a tubular opposing member comprised with an inserting end portion that can be inserted into an inner periphery of the elastic sealing member and including an annular protrusion projecting outward from its outer peripheral surface in a radial direction and being located remote from a tip end thereof; and a clamping member annularly disposed on the outer periphery of the tube, wherein the elastic sealing member is comprised of an inner tube portion with an outer peripheral surface that is fitted to an inner peripheral surface of the engaging end portion of the tube and an outer tube portion provided at one end side of the inner tube portion, being bent outwardly over as to cover the one end surface of the engaging end portion while covering the outer peripheral surface of the engaging end portion, wherein the outer peripheral surface of the inner tube portion is comprised with an annular fitting convex portion matching the annular concave portion of the tube, and the inner peripheral surface thereof with an annular fitting concave portion for fitting the annular protrusion of the opposing member, and wherein the clamping member is clamped on the outer periphery of the outer tube portion with the inserting end portion of the opposing member being inserted and attached to the inner peripheral surface of the tubular elastic sealing member.
In the present invention, the opposing member is held against the tubular elastic sealing member so as to be immovable in the axial direction owing to the above-described arrangement in which the tube is comprised with the engaging end portion with an annular concave portion being formed at a position being remote from one end surface thereof in the axial direction, in which the tubular elastic sealing member is comprised of an inner tube portion with an outer peripheral surface and fitted to an inner peripheral surface of the engaging end portion of the tube, and an outer tube portion provided at one end side of the inner tube portion, being bent outwardly over as to cover one end surface of the engaging end portion while covering the outer peripheral surface of the engaging end portion, and in which the outer peripheral surface of the inner tube portion is comprised with an annular protrusion matching the annular concave portion of the tube and the inner peripheral surface thereof with a fitting concave portion for fitting the annular protrusion of the opposing member. The tubular elastic sealing member is further held against the tube so as to be immovable in the axial direction.
One end of the tube is pinched and held between the inner tube portion and the outer tube portion of the elastic sealing member and is clamped by a clamping member from the outer periphery of the outer tube portion. Thus, it is possible to prevent the opposing member from slipping off the tube.
It is also possible to provide an annular convex portion at an intermediate portion of the engaging end portion as to project outward from the outer peripheral surface of the engaging end portion in the radial direction. The annular convex portion serving to secure creases that are generated at the engaging end portion in the course of clamping, it is enabled to improve sealing properties between the engaging end portion of the tube, the inner tube portion of the elastic sealing member, and the inserting end portion of the opposing member.
It is alternatively possible that employ an arrangement in which the annular concave portion formed on the inner peripheral surface of the engaging end portion is formed at an intermediate portion of the engaging end portion, in which the clamping member is disposed on a location closer to the one end than the annular convex portion, and in which the inner tube portion of the elastic sealing member is provided with an extension extending inward from the annular fitting convex portion of the inner tube portion in the axial direction. By the provision of the extension at the inner tube portion of the elastic sealing member, sealing between both end of the engaging end portion can be reliably performed without being affected through clamping with the extension being located remote from the portion at which clamping through the clamping member is performed.
A portion of the engaging end portion of the tube ranging from the annular concave portion to the one end surface may be formed to assume a wave-shaped tubular portion with waveforms being formed in a peripheral direction. With this arrangement, it is possible to secure sealing properties at the clamping portion and to reliably prevent leakage of fluid because generation of creases can be smoothed out through the wave-shaped tubular portions at portion where clamping of the clamping member is performed.
At least one slit extending from the one end surface in the direction of the annular concave portion may be provided at the engaging end portion of the tube in the peripheral direction thereof. With this arrangement, it is possible to secure sealing properties at the clamping portion and to reliably prevent leakage of fluid because generation of creases can be smoothed out through the slits where clamping of the clamping member is performed. Note that it is easier to form slits rather than wave-shaped tubular portions.
An inner end portion of the inner tube portion in the axial direction may be branched at an intermediate position in a thickness direction to comprise an annular outer branch portion and an inner branch portion that respectively extend outward and inward with respect to the radial direction in an inclined manner. With this arrangement, sealing properties can be favorably secured with the inner tube portion closely contacting the engaging end portion at the outer branch portion, while the inner branch portion closely contacts the opposing member for favorably securing sealing properties.
The inner tube portion may be alternatively comprised of a base portion extending outward in the axial direction from the annular fitting concave portion and an extension extending inward in the axial direction from the fitting concave portion, wherein the base portion assumes an inner diameter that is slightly larger than an outer diameter of the inserting end portion of the opposing member while the extension assumes an inner diameter that is slightly smaller than the outer diameter of the inserting end portion of the opposing member. With this arrangement, it is possible to readily insert the inserting end portion to the base portion while improving sealing properties between the elastic sealing member and the inserting end portion in the extension.
It is also possible to provide annular projecting sealing portions that coaxially project outward and inward in radial directions on a plurality of spots on the outer peripheral surface and the inner peripheral surface of the extension of the inner tube portion in the axial direction. With this arrangement, sealing properties can be favorably secured with the projecting sealing portion projecting outward of the inner tube portion closely contacting the engaging end portion, and further favorably securing sealing properties with the projecting sealing portion projecting inward of the inner tube portion closely contacting the opposing member.
The tube may be arranged either as a single-layered structure of resin, a double-layered structure with an inner layer of resin, conductive resin or metallic film and an outer layer of resin, or a triple-layered structure with an adhesive layer being formed intermediate of the inner layer and outer layer. With this arrangement, it is enabled to select tube structures in accordance with various purposes.
The elastic sealing member of the present invention may be alternatively arranged to comprise an enveloping portion covering only the one end surface of the engaging end portion of the tube and an inner tube portion including an outer peripheral surface that is fitted to the inner peripheral surface of the engaging end portion, an annular fitting convex portion formed on the outer peripheral surface of the inner tube portion that matches the annular concave portion of the tube, and an annular fitting concave portion formed on the inner peripheral surface of the inner tube portion that fits the annular protrusion of the opposing member, wherein the clamping member is clamped on the outer periphery of the engaging end portion when employing such a structure. By omitting the outer tube portion of the elastic sealing member in this manner, it is possible to readily insert the elastic sealing member to the tube while still exhibiting the above effects.