Warm hydro-forming device

A warm hydro-forming device comprises: an upper mold and a lower mold respectively mounted to an upper mold die and a lower mold die; a lifting die installed to the lower mold die through a guide unit, an upper portion of the lifting die being connected to the upper mold die through a lifting unit to cooperatively operate in an upward and downward direction with the upper mold die; a pair of hydraulic pressure cylinders for providing an axial compression force to the tube component and supplying a forming hydraulic fluid into the tube component; an ascending and descending unit for ascending or descending the upper mold die; and a heating unit associated with the lifting die such that the heating unit can move toward or away from the tube component. The heating unit heats the tube component and a forming hydraulic fluid through a high frequency induction heating.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority of Korean Application No. 10-2004-0012218, filed on Feb. 24, 2004, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a warm hydro-forming device, and more particularly, to a warm hydro-forming device in which a tube component and a forming hydraulic fluid is heated through a high frequency induction heating to a predetermined temperature at which the tube component can be easily formed.

BACKGROUND OF THE INVENTION

Generally, a hydro-forming method is performed at room temperature, e.g., in a temperature range of 10 to 30 degrees Celsius, and is one of the types of forming methods which perform expansion forming of a tube member using a hydraulic pressure. Through such a hydro-forming method, a weight of press-manufactured product that is formed as a combination of unit panels such as a front side member of a vehicle can be decreased and a manufacturing cost for the same can be reduced.

Recently, tube components that are formed through hydro-forming are generally made of high strength aluminum alloy instead of steel material to decrease weight. Such an aluminum alloy has poorer forming characteristics at room temperature than the steel material, but forming characteristics of such an aluminum alloy can be improved through a softening process. The softening process means a process to decrease a strength of the aluminum alloy as well as increase an elongation ratio of the aluminum alloy, and an annealing process is generally used as the softening process.

In order to obtain sufficient forming characteristics of the tube component that is made of a metal alloy such as an aluminum alloy, a sufficient elongation ratio must be obtained in consideration of a portion that has a maximum amount of deformation according to a shape of a formed component. The softening process is inevitable to obtain such an elongation ratio.

Referring toFIGS. 8 to 12, in a conventional hydro-forming method for an aluminum alloy, a softening process for an aluminum alloy tube component100to obtain a sufficient elongation ratio is performed at step S110.

Subsequently, as shown inFIG. 9, at step S120, the tube component100is loaded on a lower mold101. Then, as shown inFIG. 10, at step S130, an upper mold103has been descended so that the upper and lower molds are joined together, and hydraulic pressure cylinders105and107, which are disposed on both sides of the tube component100, are operated to compress the tube component100in an axial direction thereby forming a sealing within the tube component100.

Then, as shown inFIG. 11, at step S140, a forming hydraulic fluid is supplied into the tube component100from the hydraulic pressure cylinders105and107. Consequently, the tube component100is expanded to forming surfaces109and111that are formed on the upper mold103and the lower mold101.

After the tube component100is formed, the tube component is extracted from the lower and upper molds101and103at step S150. In addition, a hardening process for the tube component100is performed to increase a strength of the tube member that is weakened by the softening process. Such a hardening process may deteriorate a quality of the formed tube component and a productivity of the forming process.

Meanwhile, a warm hydro-forming method has been introduced, in which a tube component is heated in order to increase the forming characteristics of the tube component. A warm hydro-forming device for performing a warm hydro-forming method generally comprises heating means such as heating coils that are disposed within an upper mold and a lower mold.

However, conventional heating means were not effective for heating the tube member. In particular, if the tube component is heated by heat of the heating coils that are disposed within the upper and lower molds, the heating efficiency is not good. That is, only a portion of heat of the heating coil is transmitted to the tube component, and a majority portion of the heat is dissipated through the molds. In addition, because the heating coils are disposed within the upper and lower molds, it becomes difficult to manufacture such molds.

SUMMARY OF THE INVENTION

The motivation for the present invention is to provide a warm hydro-forming device that effectively heats a tube component with a high frequency induction heating.

An exemplary warm hydro-forming device according to an embodiment of the present invention comprises: first and second molds, such as an upper mold and a lower mold, being respectively provided with a forming surface for an expansion forming of a tube component and respectively mounted to first and second mold dies, such as an upper mold die and a lower mold die, to respectively compress first and second portions of the tube component, such as an upper portion and a lower portion of the tube component; a lifting die installed to the second mold die through a guide unit to be disposed around the second mold, a first portion of the lifting die, such as an upper portion of the lifting die, being connected to the first mold die through a lifting unit to cooperatively operate in a predetermined direction, such as an upward and downward direction, with the first mold die; a pair of hydraulic pressure cylinders for providing an axial compression force to the tube component by compressing both ends thereof in an axial direction, the hydraulic pressure cylinders supplying a forming hydraulic fluid into the tube component to generate a forming hydraulic pressure for forming the tube component; a positioning unit, such as an ascending and descending unit, fixed to an external fixture for positioning the first mold die, such as by ascending or descending the first mold die; and a heating unit associated with the lifting die such that the heating unit can move toward or away from the tube component, the heating unit heating the tube component and a forming hydraulic fluid within the tube component through a high frequency induction heating at a predetermined temperature.

A forming steel may be respectively disposed on the forming surface of the first and second molds.

The guide unit may comprise: a guide pin mounted, such as vertically, to the second mold die; and a guide hole formed in a portion, such as a lower portion, of the lifting die to receive the guide pin and thereby guiding the guide pin.

The lifting unit may comprise: pin holes formed in the first mold die and in the lifting die; and a lifting pin that is inserted into the pin holes and provided with a stopper at both ends thereof, to move the lifting die in response to movement of the first mold die.

The pair of hydraulic pressure cylinders may be mounted to the lifting die on both sides of a longitudinal direction of the tube component.

The positioning unit may comprise a hydraulic cylinder that is actuated by a hydraulic pressure, and a rod of the hydraulic cylinder is connected to the first mold die, such as at a first end of the rod.

The heating unit may comprise: an outer housing slidably disposed on a rail of a guide frame that is disposed on an opposite side of the lifting die, a front surface of the outer housing being opened and the outer housing defining a space portion therein; a guide housing slidably disposed within the space portion of the outer housing, a front surface of the guide housing being opened and the guide housing defining a space portion therein, two guide rails being respectively provided on both inner side surfaces of the guide housing, the two guide rails gradually widening toward an opened surface of the guide housing, and a plurality of slots being formed in a rear surface of the guide housing; first and second heating heads, such as upper and lower heating heads, both sides of which are slidably connected to the guide rails of the guide housing, and first and second heating heads being connected to an external high frequency induction heater; a forward and rearward movement plate disposed in a rear portion of the guide housing within the space portion of the outer housing, the forward and rearward movement plate being connected to the first and second heating heads through a plurality of guide beams that are inserted into the slots formed in the rear surface of the guide housing; first and second coil holders, such as upper and lower coil holders, connected respectively to the first and second heating heads through operating coils, and high frequency coils being respectively wound in inner portions thereof; a holding cylinder fixed to the forward and rearward movement plate and urging the guide housing to move in a forward or rearward direction with respect to the forward and rearward movement plate; a first forward and rearward movement cylinder fixed to the guide frame and urging the outer housing to move with respect to the guide frame; and a pair of second forward and rearward movement cylinders fixed to the outer housing and urging the forward and rearward movement plate to move in a front or rear direction with respect to the outer housing.

The outer housing may be formed as a rectangular shape, and a supporting stopper is provided at a corner of a rear surface of the outer housing.

The holding cylinder may be a pneumatic cylinder. In addition, each of the first forward and rearward movement cylinders and the second forward and rearward movement cylinders may be a pneumatic cylinder.

The guide beams may be connected through the guide slot to the forward and rearward movement plate such that the guide beams can move in a predefined direction, such as upwardly and downwardly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A warm hydro-forming device according to an embodiment of the present invention can heat a tube component at a predetermined temperature (for example, a temperature within a temperature range of 50 to 300 degrees Celsius), and then forms the tube component by supplying a forming hydraulic fluid into the tube component.

FIG. 1is a schematic sectional view of a warm hydro-forming device according to an embodiment of the present invention, andFIG. 2is a sectional view along a line A—A inFIG. 1.

With reference toFIG. 1, an upper mold die1is provided and a lower mold die3is provided below the upper mold die1.

An upper mold7and a lower mold9are respectively mounted to the upper mold die1and the lower mold die3to respectively compress an upper portion and a lower portion of the tube component5, and the upper and lower molds7and9are respectively provided with a forming surface for a tube component5that will be formed.

Forming steels11are respectively disposed on the forming surface of the upper and lower molds7and9.

A lifting die13is disposed around the lower mold9. The lifting die13is installed to the lower mold die3through a guide unit, and an upper portion of the lifting die13is connected to the upper mold die1through a lifting unit17to cooperatively operate in an upward and downward direction with the upper mold die1.

The guide unit15may comprise a guide pin19and a guide hole21. The guide pin19is vertically mounted to the lower mold die3, and the guide hole21is formed in a lower portion of the lifting die13to receive the guide pin19and thereby guiding the guide pin19.

The lifting unit17may comprise pin holes23and a lifting pin25. The pin holes23are formed respectively in the upper mold die1and the lifting die17, and the lifting pin25is inserted into the pin holes23and provided with stoppers27at both ends thereof so that the lifting pin25ascends the lifting die13after a specific time in response to an upward movement of the upper mold die1.

As shown inFIG. 2, a pair of hydraulic pressure cylinders29and31are installed on both sides of the lifting die13. The hydraulic pressure cylinders29and31provide an axial compression force by compressing both ends of the tube component5in an axial direction through punches33and35, and supply a forming hydraulic fluid into the tube component5to generate a forming hydraulic pressure for forming the tube component5.

The pair of hydraulic pressure cylinders29and31are mounted to the lifting die13through mounting brackets37at a specific level, on both sides of a longitudinal direction of the tube component5, so that the hydraulic pressure cylinders29and31ascend and descend with the lifting die13.

As shown inFIG. 1, an ascending and descending unit41is fixed to an external fixture39, and ascends or descends the upper mold die1. The ascending and descending unit41may include a hydraulic cylinder that is actuated by a hydraulic pressure and a front end of an operating rod which is connected to the upper mold die1to ascend or descend the upper mold die1.

A guide frame47is provided on one side of the lifting die13along a direction perpendicular to the longitudinal direction of the tube component5, and a rail49is formed on the guide frame47along a longitudinal direction of the guide frame47.

A heating unit51is associated with the lifting die13such that the heating unit51can move toward or away from the tube component5that is fixed by punches33and35of the hydraulic pressure cylinders29and31. That is, the heating unit51is slidably connected to the rail49to move toward of away from the tube component5. The heating unit51may be configured to surround the tube component5and transmit heat to the tube component5through a high frequency induction heating, thereby heating the tube component and the forming hydraulic fluid within the tube component5.

As shown inFIG. 3, an outer housing53is slidably disposed on the rail49of the guide frame49that is disposed on an opposite side of the lifting die13, and a front surface of the outer housing53is opened. The outer housing53defines a space portion therein, and is formed as a rectangular shape.

A guide housing55is slidably disposed within the space portion of the outer housing53. A front surface of the guide housing55is opened, and the guide housing55defines a space portion therein.

Two guide rails57and59are respectively provided on both inner side surfaces of the guide housing55. The two guide rails57and59gradually widen toward an opened surface of the guide housing55, and a plurality of slots61are formed in a rear surface of the guide housing55.

Upper and lower heating heads63and65are disposed within an inner space portion of the guide housing55. Both sides of the upper and lower heating heads63and65are slidably connected to the guide rails57and59of the guide housing55, so that the upper and lower heating heads63and65can move on the guide rails57and59while approaching to each other or departing from each other. The upper and lower heating heads63and65are connected to an external high frequency induction heater67, as shown inFIG. 1.

A forward and rearward movement plate69is disposed in a rear portion of the guide housing55within the inner space portion of the outer housing53. The forward and rearward movement plate69is connected to the upper and lower heating heads63and65through a plurality of guide beams71that are inserted into the slots61formed in the rear surface of the guide housing55. The guide beams71move up and down within the slots61while the upper and lower heating heads63and65move. That is, the guide beams71are connected through the guide slots61to the forward and rearward movement plate69such that the guide beams71can move upwardly or downwardly.

Supporting stoppers73are provided at corners of a rear surface of the outer housing to support the rear surface of the guide housing55.

Upper and lower coil holders79and81are connected respectively to the upper and lower heating heads63and65through operating coils83, and high frequency coils77, which are connected to the operating coils83, are respectively wound in inner portions of the upper and lower coil holders79and81as shown inFIGS. 2 and 3.

A holding cylinder85is fixed to a center portion of the forward and rearward movement plate69. The holding cylinder85urges the guide housing55to move in a forward or rearward direction with respect to the forward and rearward movement plate69. The holding cylinder85may include an operating rod87that is fixedly connected to the rear surface of the guide housing55.

A first forward and rearward movement cylinder89is fixed to an outer portion of the guide frame47, the first forward and rearward movement cylinder89urges the outer housing53to move with respect to the guide frame. The first forward and rearward movement cylinder89may include an operating rod91that is fixedly connected to the rear surface of the outer housing53.

A pair of second forward and rearward movement cylinders93are fixed to the outer housing53. The second forward and rearward movement cylinders93urge the forward and rearward movement plate69to move in a front or rear direction with respect to the outer housing53. The second forward and rearward movement cylinders93may include an operating rod95that is fixedly connected to the rear surface of the forward and rearward movement plate69.

The holding cylinder85may be a pneumatic cylinder having a pneumatic pressure as an operating pressure, and the first and second forward and rearward movement cylinders91and93may also be a pneumatic cylinder.

According to the warm hydro-forming device of the embodiment of the present invention, the tube component (e.g., made of aluminum alloy)5disposed between the molds7and9is expanded along the forming surface formed in the molds7and9by the axial compression of the hydraulic pressure cylinders29and31and a hydraulic pressure of the forming hydraulic pressure fluid supplied into the tube component5. At this time, the tube component5is heated to a specific temperature by the heating unit51after the forming hydraulic fluid is supplied into the tube component5, so that the tube component5and the forming hydraulic fluid within the tube component5are heated to a specific temperature. Then, the forming hydraulic fluid is finally supplied into the tube component5to expand the tube component5.

If the tube component5is made of aluminum alloy, the tube component5is preferably heated within a temperature range of 50 to 300 degrees Celsius in which the tensile strength decreases a little bit but the elongation ratio of aluminum alloy increases rapidly.

FIG. 7illustrates a correlation between the tensile strength and the elongation ratio of an aluminum alloy tube component (e.g., AL 7075 tube component). As shown inFIG. 7, the tensile strength is in a range of 570 MPa to 525 MPa and the elongation ratio is in a range of 11% to 14% in a temperature range of 25 degrees Celsius to 100 degrees Celsius, however, in a high temperature range of 150 degrees Celsius to 370 degrees Celsius the tensile strength rapidly decreases from 285 MPa to 40 MPa but the elongation ratio rapidly increases from 23% to 70%.

Because the hydro-forming is performed at the high temperature, a silicon oil, that may operate stably at a high temperature range of 150 degrees Celsius to 370 degrees Celsius, is suitable for the forming hydraulic fluid.

The warm hydro-forming device according to an embodiment of the present invention operates as follows. At first, as shown inFIGS. 1 and 2, the tube component5is fixed and sealed by the punches33and35of the hydraulic pressure cylinders29and31in a state in which the upper mold and lower molds are separated from each other, and the forming hydraulic fluid is supplied into the tube component5.

Then, by forwardly operating the first forward and rearward movement cylinder89of the heating unit51, the outer housing53is moved toward the tube component5on the rail49of the guide frame47.

Then, as shown inFIG. 3, by forwardly operating the second forward and rearward movement cylinder93, the guide housing55is forwardly moved with respect to the outer housing53, so that the upper and lower coil holders79and81are disposed at the upper and lower portions of the tube component5that is supported by the hydraulic pressure cylinders29and31.

As shown inFIG. 4, if the holding cylinder85forwardly operates in this state, i.e., if the holding cylinder85moves the guide housing55in a forward direction with respect to the forward and rearward movement plate69, the upper and lower heating heads63and65, that are maintained at a constant distance from the forward and rearward movement plate69by the guide beams71, approach together while moving on the guide rails57and59formed on the side surfaces of the guide housing55.

Then, a distance between the heating heads63and65is decreased, so that the upper and lower coil holders79and81surround upper and lower portions of the tube component5that is supported by the hydraulic pressure cylinders29and31. Under this situation, a high frequency signal is outputted from the high frequency induction heater67, and thereby the tube component5and the forming hydraulic fluid within the tube component5are heated to the specific temperature by the high frequency induction heating.

After the heating, the heating unit51is retreated in a reverse sequence. Rearward operations of the holding cylinder85, the second forward and rearward movement cylinder93, and the first forward and rearward movement cylinder89are sequentially performed, so that the upper and lower coil holders79and81are deviated from the upper and lower molds7and9as shown inFIG. 5. Finally, the heating unit51is in state shown inFIG. 6.

After the forming hydraulic fluid and the tube component5are heated to the specific temperature and the heating unit51is retreated, the hydraulic cylinder45of the ascending and descending unit41descends the upper mold die1. As shown inFIG. 5, if the upper mold die1is being descended, the lifting die13is also being descended and simultaneously the hydraulic pressure cylinders29and31and the upper mold7are also descended. Accordingly, the tube component5is pressurized between the upper and lower molds7and9.

By supplying the forming pressure into the tube component5under this condition, the tube component5is extended along the forming surface.

Finally, the formed tube component5is extracted from the upper and lower molds7and9, and is then cooled.

According to an embodiment of the present invention, because the tube component is heated by a high frequency induction heating, the tube component is effectively and easily heated. Furthermore, because the heating unit automatically moves toward and away from the tube component that is supported by the hydraulic pressure cylinders between the upper and lower molds, a process for heating the tube component becomes very simple.