Method of Hydraulic bulging and shaft pressing profile element pipe to make hydraulically bulged product

Abstract

A profile element pipe for hydraulic bulging of the present invention has a peripheral length with an outer diameter gradually increasing or decreasing from one axial side toward the other thereof and has a parallel part formed on at least one end thereof. According to a bulging device and a bulging method using this profile element pipe, for example, even when a profile steel pipe having a cross sectional shape varying in the axial direction as in a tapered pipe is hydraulically bulged, a bulging in which an internal pressure loading and an shaft pressing are combined with each other can be performed to provide a larger expansion ratio than a conventional case and a joining and socket connection thereof to the other part can also be easily performed.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a profile element pipe for hydraulic bulging, a hydraulic bulging device using the profile element pipe, a hydraulic bulging method using the profile element pipe, and a hydraulically bulged product subjected to the hydraulic bulging. [0003] 2. Description of the Related Art [0004] A hydraulic bulging has more merits as compared with other forming or forming methods. For example, since a profile element pipe can be hydraulically bulged to such an intricate configuration part having different cross-sections in the longitudinal direction of the product, machine parts, which require welding and joining in a conventional method, can be formed in one-piece. Further, since the hydraulic bulging generates work hardening over the entire hydraulically bulged portions, even if a soft element pipe is used, a product having high strength can be obtained. [0005] Further, in the hydraulic bulging,...

AI Technical Summary

Benefits of technology

"The present invention provides a profile element pipe for hydraulic bulging that has a varied peripheral length over the axial length with an outer diameter gradually increasing or decreasing from one axial side toward the other, and a parallel part formed on at least one pipe end thereof. The length of the parallel part is preferably not less than the total of an amount of shaft pressing performed in the hydulic bulbing and a length necessary for sealing during bulging. The radius R of curvature of a corner part in the parallel part is varied in accordance with a change of a peripheral length. The profile element pipe can be used in a hydraulic bulging device by providing parallel parts on at least one of end portion inner surfaces of both an upper die and a lower die and on an outer surface of a shaft pressing tool which matches with pipe-end inner surfaces. The present invention allows for a larger pipe expansion ratio and easy joining with other parts."

Problems solved by technology

Further, the hydraulic bulging has a problem attributable to a shape of the element pipe.

As described above, even if an intricate configuration having different axial cross-sectional shapes can be obtained as one of the merits of the hydraulic bulging, the configuration of a worked product which can be obtained is limited.

However, when hydraulic bulging is performed by using a tapered element pipe whose cross-sectional shape varies in the axial direction, in case of using a shaft pressing tool for the straight element pipe shown in FIG. 1, it is found difficult to apply the shaft pressing on the tapered element pipe.

However, as a shaft pressing tool 4 advances into forms 1 and 2 with the shaft pressing, insufficient restriction of inner and outer surfaces of the tapered element pipe TP1 by the shaft pressing tool 4 side take places, thus likely leading up to seal leakage occurs.

However, since shaft pressing cannot be performed, hydraulic bulging is generally completed only by loading internal pressure without shaft pressing.

Therefore, in the hydraulic bulging, a merit of using the tapered element pipe is not in fact fully utilized.

When hydraulic bulging is performed in a conventional tapered element pipe, there is a problem which arises when a hydraulically bulged product is joined with another member, other than the problem that shaft pressing is difficult.

Thus, since accuracy cannot be ensured in welding and joining with another member, the joining with another member or the like is not easy.

Further, when an end of the pipe is socketed into another part and connected thereto, that is a socket connection, the accuracy cannot be ensured as well.

Thus positioning of the tapered element pipe becomes difficult.

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