Patent Description:
For example, a forming device described in PTL <NUM> has been known as a forming device that forms a metal pipe having a pipe part and a flange part. The forming device described in PTL <NUM> includes: a pair of an upper die and a lower die and a gas supply part that supplies a high-pressure gas that is a gas into a metal pipe material held between the upper die and the lower die. By combining the upper die and the lower die together, a main cavity part for forming a pipe part and a sub-cavity part that communicates with the main cavity part to form a flange part are configured between the upper die and the lower die. In this forming device, a metal pipe material is expanded with the supply of a gas into the metal pipe material in a case where the upper die and the lower die are closed. Accordingly, the pipe part and the flange part can be simultaneously formed.

Specifically, parting surfaces (matching surfaces) of the upper die and the lower die are formed in steps toward the center from the outside. When the upper die and the lower die are closed, a main cavity part as a forming space is formed between the parting surfaces at the center of the upper die and the lower die, and a sub-cavity part is formed as a forming space communicating with the main cavity part on a side of the main cavity part between the parting surfaces of the upper die and the lower die. The sub-cavity part is closed by the stepped parting surfaces of the upper die and the lower die and becomes a closed space in the die.

Here, in the forming device, as described above, a sub-cavity part corresponding to a shape (thickness and length) of a flange part becomes a closed space in the die. Accordingly, in a case where the flange part is formed with the supply of a high-pressure gas, there is a concern that the flange part may deform, and a flange part having a desired shape may not be formed.

Accordingly, in order to prevent the deformation of the flange part, it is considered that the sub-cavity part that is a forming space is expanded to the outside of the die to make it open to the outside. However, in a case where the sub-cavity part is made open to the outside, there is a concern that foreign matter such as fragments may fly to the outside of the die and scatter to the surroundings in a case where it is assumed that a material itself has a low strength, and thus a metal pipe bursts due to a high-pressure gas in the die.

The invention is contrived to solve the problem, and an object of an aspect of the invention is to provide a forming device that can prevent foreign matter such as fragments generated in a die from scattering to the surroundings of the die.

According to an aspect of the invention, there is provided a forming device that expands a metal pipe material to form a metal pipe, the device including: an upper die and a lower die that form a main cavity part forming a main body part of the metal pipe and a sub-cavity part forming a flange part of the metal pipe by surfaces thereof opposed to each other; a shielding member that prevents foreign matter discharged from the main cavity part or the sub-cavity part from scattering; a heating mechanism that energizes the metal pipe material to heat the metal pipe material; and a gas supply part for supplying a gas for expanding the metal pipe material into the metal pipe material held between the lower die and the upper die and heated by the heating mechanism, in which the sub-cavity part is extended to be opened to the outside of the die in a direction crossing an extending direction of the metal pipe material, and the shielding member is provided on a line in which the sub-cavity part extends in the expanding of the metal pipe material.

According to the forming device, in the expanding and forming of the metal pipe material between the upper die and the lower die, foreign matter such as fragments may be generated in the main cavity part or the sub-cavity part. In this case, the foreign matter moves outward in the extending direction of the sub-cavity part, crossing the extending direction of the metal pipe material. The foreign matter is prevented from advancing by the shielding member provided on the extending line of the sub-cavity part in the expanding of the metal pipe material. Accordingly, the foreign matter discharged from the main cavity part or the sub-cavity part can be prevented from scattering to the surroundings of the die.

Here, the shielding member may block the sub-cavity part from a direction in which the sub-cavity part is extended. In a case where such a configuration is employed, the sub-cavity part is blocked from the extending direction of the sub-cavity part, and thus the foreign matter can be securely prevented from scattering to the surroundings of the die without being discharged to the outside of the die.

In addition, the shielding member may be provided to be brought into contact with a side surface of the upper die or the lower die and may be moved with the movement of the upper die or the lower die to block the sub-cavity part from the direction in which the sub-cavity part is extended in a case where the die is closed. In a case where such a configuration is employed, a die holder holding the die can be used as the shielding member and there is no need to provide a separate shielding member. In addition, in a case where the shielding member is provided to be brought into contact with a side surface of the upper die, in a state in which the shielding member is released from the die, the shielding member is separated upward from the lower die together with the upper die. Accordingly, for example, in a case where the metal pipe material is inserted into the lower die or in a case where the formed metal pipe is detached from the lower die, the shielding member does not become a hindrance.

According to an aspect of the invention, it is possible to suppress the scattering of foreign matter such as fragments generated in a die to the surroundings of the die.

Hereinafter, preferable embodiments of a forming device according to an aspect of the invention will be described with reference to the drawings. In the drawings, the same or similar parts will be denoted by the same reference signs, and overlapping description will be omitted.

<FIG> is a schematic diagram of a configuration of a forming device. <FIG> is a transverse sectional view of a blow forming die, an upper die holding part, and a lower die holding part, taken along the line II-II of <FIG>. As shown in <FIG>, a forming device <NUM> that forms a metal pipe <NUM> (see <FIG>) is provided with a blow forming die <NUM> composed of a pair of a lower die <NUM> and an upper die <NUM>, a lower die holding part <NUM> for holding the lower die <NUM>, an upper die holding part <NUM> for holding the upper die <NUM>, a driving mechanism <NUM> that moves at least one of the lower die holding part <NUM> holding the lower die <NUM> and the upper die holding part <NUM> holding the upper die <NUM> (here, upper die holding part <NUM>), a pipe holding mechanism <NUM> that holds a metal pipe material <NUM> shown by the virtual line between the lower die <NUM> and the upper die <NUM>, a heating mechanism <NUM> that energizes the metal pipe material <NUM> held by the pipe holding mechanism <NUM> to heat the metal pipe material, a gas supply part <NUM> for supplying a high-pressure gas (gas) into the metal pipe material <NUM> held and heated between the lower die <NUM> and the upper die <NUM>, a pair of gas supply mechanisms <NUM> for supplying a gas into the metal pipe material <NUM> held by the pipe holding mechanism <NUM> from the gas supply part <NUM>, and a water circulation mechanism <NUM> that forcibly cools the blow forming die <NUM> with water. In addition, the forming device <NUM> is provided with a controller <NUM> that controls driving of the driving mechanism <NUM>, driving of the pipe holding mechanism <NUM>, driving of the heating mechanism <NUM>, and gas supply of the gas supply part <NUM>.

The lower die <NUM> is fixed to a large base <NUM> via the lower die holding part <NUM>. The lower die <NUM> is composed of a large steel block and is provided with a recessed part <NUM> in an upper surface thereof (a parting surface from the upper die <NUM>). As shown in <FIG> and <FIG>, the lower die holding part <NUM> holding the lower die <NUM> is provided with a lower die holder <NUM> holding the lower die <NUM>, a lower die holder <NUM> holding the lower die holder <NUM>, and a lower die base plate <NUM> holding the lower die holder <NUM>, that are laminated in order from the top. The lower die base plate <NUM> is fixed to the base <NUM>. As shown in <FIG>, lengths of the lower die holder <NUM> and the lower die holder <NUM> in an axial direction (lengths in the horizontal direction in <FIG>) are almost the same as that of the lower die <NUM> in the axial direction.

An electrode storage space 11a is provided near each of right and left ends (right and left ends in <FIG>) of the lower die <NUM>, and a first electrode <NUM> and a second electrode <NUM> that are configured to advance or retreat in a vertical direction by an actuator (not shown) are provided in the electrode storage spaces 11a. Recessed grooves 17a and 18a having a semi-arc shape corresponding to an outer peripheral surface on the lower side of the metal pipe material <NUM> are formed in upper surfaces of the first electrode <NUM> and the second electrode <NUM>, respectively (see <FIG>). The metal pipe material <NUM> can be placed to be well fitted in the recessed grooves 17a and 18a. In addition, in front surfaces of the first and second electrodes <NUM> and <NUM> (surfaces of the die in an outward direction), tapered recessed surfaces 17b and 18b are formed such that the vicinities thereof are recessed at an angle into a tapered shape toward the recessed grooves 17a and 18a, respectively. In addition, the lower die <NUM> has a cooling water passage <NUM> formed therein and is provided with a thermocouple <NUM> inserted from the bottom at a substantially center thereof. This thermocouple <NUM> is supported movably up and down by a spring <NUM>.

The pair of first and second electrodes <NUM> and <NUM> positioned in the lower die <NUM> constitute the pipe holding mechanism <NUM>, and can elevatably support the metal pipe material <NUM> between the upper die <NUM> and the lower die <NUM>. The thermocouple <NUM> is just an example of the temperature measuring unit, and a non-contact temperature sensor such as a radiation thermometer or an optical thermometer may be provided. A configuration without the temperature measuring unit may also be employed if the correlation between the energization time and the temperature can be obtained.

The upper die <NUM> is a large steel block that is provided with a recessed part <NUM> in a lower surface thereof (a parting surface from the lower die <NUM>) and a cooling water passage <NUM> built therein. As shown in <FIG> and <FIG>, the upper die holding part <NUM> holding the upper die <NUM> is provided with an upper die holder <NUM> holding the upper die <NUM>, an upper die holder <NUM> holding the upper die holder <NUM>, and an upper die base plate <NUM> holding the upper die holder <NUM>, that are laminated in order from the bottom. The upper die base plate <NUM> is fixed to a slide <NUM>. As shown in <FIG>, lengths of the upper die holder <NUM> and the upper die holder <NUM> in an axial direction (lengths in the horizontal direction in <FIG>) are almost the same as that of the upper die <NUM> in the axial direction. The slide <NUM> to which the upper die holding part <NUM> is fixed is suspended by a pressing cylinder <NUM>, and is guided by a guide cylinder <NUM> so as not to laterally vibrate.

Similarly to the case of the lower die <NUM>, an electrode storage space 12a is provided near each of right and left ends (right and left ends in <FIG>) of the upper die <NUM>, and a first electrode <NUM> and a second electrode <NUM> that are configured to advance or retreat in the vertical direction by an actuator (not shown) are provided in the electrode storage spaces 12a. Recessed grooves 17a and 18a having a semi-arc shape corresponding to an outer peripheral surface on the upper side of the metal pipe material <NUM> are formed in lower surfaces of the first and second electrodes <NUM> and <NUM>, respectively (see <FIG>), and the metal pipe material <NUM> can be well fitted in the recessed grooves 17a and 18a. In addition, in front surfaces of the first and second electrodes <NUM> and <NUM> (surfaces of the die in an outward direction), tapered recessed surfaces 17b and 18b are formed such that the vicinities thereof are recessed at an angle into a tapered shape toward the recessed grooves 17a and 18a, respectively. Accordingly, in a case where the pair of first and second electrodes <NUM> and <NUM> positioned in the upper die <NUM> also constitute the pipe holding mechanism <NUM> and the metal pipe material <NUM> is sandwiched between the upper and lower pairs of first and second electrodes <NUM> and <NUM> from the vertical direction, the metal pipe material <NUM> can be surrounded such that the outer periphery thereof firmly adheres well over the whole periphery. The fixing parts of the respective actuators moving the first electrode <NUM> and the second electrode <NUM> corresponding to a moving part up and down are held and fixed to the lower die holding part <NUM> and the upper die holding part <NUM>, respectively.

The driving mechanism <NUM> is provided with a slide <NUM> that moves the upper die <NUM> and the upper die holding part <NUM> so as to combine the upper die <NUM> and the lower die <NUM> together, a driving part <NUM> that generates a driving force for moving the slide <NUM>, and a servo motor <NUM> that controls a fluid amount with respect to the driving part <NUM>. The driving part <NUM> is composed of a fluid supply part that supplies a fluid (an operating oil in a case where a hydraulic cylinder is employed as the pressing cylinder <NUM>) for driving the pressing cylinder <NUM> to the pressing cylinder <NUM>.

The controller <NUM> can control the movement of the slide <NUM> by controlling the amount of the fluid to be supplied to the pressing cylinder <NUM> by controlling the servo motor <NUM> of the driving part <NUM>. The driving part <NUM> is not limited to a part that applies a driving force to the slide <NUM> via the pressing cylinder <NUM> as described above. For example, the driving part may be mechanically connected to the slide <NUM> to directly or indirectly apply a driving force generated by the servo motor <NUM> to the slide <NUM>. For example, a driving mechanism having an eccentric shaft, a driving source (for example, a servo motor and a reducer) that applies a rotating force for rotating the eccentric shaft, and a converter (for example, a connecting rod or an eccentric sleeve) that converts the rotational movement of the eccentric shaft into the linear movement to move the slide may be employed. In this embodiment, the driving part <NUM> may not have the servo motor <NUM>.

As shown in <FIG>, an upper end surface of the lower die <NUM> and a lower end surface of the upper die <NUM> are uneven. Specifically, the recessed part <NUM> with a rectangular cross-sectional shape is formed at the center of the upper end surface of the lower die <NUM>, and the recessed part <NUM> with a rectangular cross-sectional shape is formed at the center of the lower end surface of the upper die <NUM> to be opposed to the recessed part <NUM> of the lower die <NUM>.

The lower die holder <NUM> that constitutes the lower die holding part <NUM> and holds the lower die <NUM> is provided with a recessed part 93a with a rectangular cross-sectional shape at a center of an upper end surface 93e of the rectangular parallelepiped. The lower die <NUM> is held such that the substantially lower half thereof is fitted into a recessed part 93c with a rectangular cross-sectional shape provided at the center of a bottom surface 93d of the recessed part 93a. Spaces S1 and S2 are respectively provided between protrusions 93b at both sides that form the recessed part 93a of the lower die holder <NUM> and side surfaces of the substantially upper half of the lower die <NUM> that protrude higher than the bottom surface 93d of the lower die holder <NUM>. Protrusions 96b of the upper die holder <NUM> to be described later proceed into the spaces S1 and S2 in a case where the blow forming die <NUM> is closed.

The upper die holder <NUM> that constitutes the upper die holding part <NUM> and holds the upper die <NUM> is formed into a stepped block shape, in which the rectangular parallelepiped becomes smaller downward in a stepwise manner, by forming two steps toward the lower side from the upper side at both sides of the rectangular parallelepiped. A recessed part 96a with a rectangular cross-sectional shape is formed at a center of a lower end surface 96d of the upper die holder <NUM>, and the upper die <NUM> is held to be housed in the recessed part 96a. Accordingly, inner surfaces of the protrusions 96b at both sides that form the recessed part 96a of the upper die holder <NUM> are brought into contact with the side surfaces of the upper die <NUM>. In addition, the protrusions 96b protrude downward from the lower end surface of the upper die <NUM> by a predetermined length, and respectively proceed into the spaces S1 and S2 of the lower die holder <NUM> in a case where the blow forming die <NUM> is closed. In addition, in a case where the blow forming die <NUM> is closed, the lower end surface (tip end surface) 96d of the protrusion 96b of the upper die holder <NUM> is brought into contact with the bottom surface 93d of the recessed part 93a of the lower die holder <NUM>, and step surfaces 96e that form the protrusions 96b at both sides of the protrusions 96b of the upper die holder <NUM> and are positioned above the protrusions 96b are brought into contact with the upper end surfaces 93e of the protrusions 93b of the lower die holder <NUM>.

As shown in <FIG>, the heating mechanism <NUM> has a power supply <NUM>, conductive wires <NUM> that extend from the power supply <NUM> and are connected to the first electrodes <NUM> and the second electrodes <NUM>, and a switch <NUM> that is provided in the conductive wire <NUM>. The controller <NUM> controls the heating mechanism <NUM>, and thus the metal pipe material <NUM> can be heated to a quenching temperature (equal to or higher than an AC3 transformation temperature).

Each of the pair of gas supply mechanisms <NUM> has a cylinder unit <NUM>, a cylinder rod <NUM> that advances or retreats in accordance with the operation of the cylinder unit <NUM>, and a sealing member <NUM> that is connected to a tip end of the cylinder rod <NUM> on the side of the pipe holding mechanism <NUM>. The cylinder unit <NUM> is placed and fixed on the base <NUM> via a block <NUM>. A tapered surface <NUM> is formed at a tip end of the sealing member <NUM> so as to be tapered. The tapered surfaces are formed into such a shape as to be well fitted in and brought into contact with the tapered recessed surfaces 17b and 18b of the first and second electrodes <NUM> and <NUM> (see <FIG>). The sealing member <NUM> is provided with a gas passage <NUM> that extends from the cylinder unit <NUM> toward the tip end, specifically, through which a high-pressure gas supplied from the gas supply part <NUM> flows as shown in <FIG>.

As shown in <FIG>, the gas supply part <NUM> includes a high-pressure gas supply <NUM>, an accumulator <NUM> that stores a gas supplied by the high-pressure gas supply <NUM>, a first tube <NUM> that extends from the accumulator <NUM> to the cylinder unit <NUM> of the gas supply mechanism <NUM>, a pressure control valve <NUM> and a switching valve <NUM> that are provided in the first tube <NUM>, a second tube <NUM> that extends from the accumulator <NUM> to the gas passage <NUM> formed in the sealing member <NUM>, and a pressure control valve <NUM> and a check valve <NUM> that are provided in the second tube <NUM>. The pressure control valve <NUM> functions to supply, to the cylinder unit <NUM>, a gas having an operation pressure adapted for the pressing force of the sealing member <NUM> with respect to the metal pipe material <NUM>. The check valve <NUM> functions to prevent the high-pressure gas from flowing backward in the second tube <NUM>.

The controller <NUM> controls the pressure control valve <NUM> of the gas supply part <NUM>, and thus a gas having a desired operation pressure can be supplied into the metal pipe material <NUM>. In addition, the controller <NUM> acquires temperature information from the thermocouple <NUM> by the transmission of the information from (A) shown in <FIG>, and controls the pressing cylinder <NUM> and the switch <NUM>.

The water circulation mechanism <NUM> includes a water tank <NUM> that stores water, a water pump <NUM> that draws up and pressurizes the water stored in the water tank <NUM> to send the water to the cooling water passage <NUM> of the lower die <NUM> and the cooling water passage <NUM> of the upper die <NUM>, and a pipe <NUM>. Although omitted, a cooling tower that lowers the water temperature or a filter that purifies the water may be provided in the pipe <NUM>.

Next, a method of forming a metal pipe using the forming device <NUM> will be described. <FIG> show steps from a pipe injection step for injecting the metal pipe material <NUM> as a material to an energization and heating step for heating the metal pipe material <NUM> by energization. More specifically, <FIG> is a diagram showing a state in which the metal pipe material is set in the die. <FIG> is a diagram showing a state in which the metal pipe material is held by the electrodes. <FIG> is a diagram showing a manufacturing step following the steps in <FIG>.

First, a metal pipe material <NUM> that is a quenchable steel type is prepared. As shown in <FIG>, the metal pipe material <NUM> is placed (injected) on the first and second electrodes <NUM> and <NUM> provided in the lower die <NUM> using, for example, a robot arm or the like. Since the first and second electrodes <NUM> and <NUM> have the recessed grooves 17a and 18a, respectively, the metal pipe material <NUM> is positioned by the recessed grooves 17a and 18a. Next, the controller <NUM> (see <FIG>) controls the pipe holding mechanism <NUM> to hold the metal pipe material <NUM> by the pipe holding mechanism <NUM>. Specifically, as in <FIG>, an actuator that allows the first and second electrodes <NUM> and <NUM> to advance or retreat is operated such that the first and second electrodes <NUM> and <NUM> positioned on the upper and lower sides, respectively, are brought closer to and into contact with each other. Due to this contact, both of the end parts of the metal pipe material <NUM> are sandwiched between the first and second electrodes <NUM> and <NUM> from the upper and lower sides. In addition, due to the presence of the recessed grooves 17a and 18a formed in the first and second electrodes <NUM> and <NUM>, the metal pipe material <NUM> is sandwiched so as to firmly adhere over the whole periphery thereof.

Next, as shown in <FIG>, the controller <NUM> controls the heating mechanism <NUM> to heat the metal pipe material <NUM>. Specifically, the controller <NUM> turns on the switch <NUM> of the heating mechanism <NUM>. In that case, electric power is supplied from the power supply <NUM> to the metal pipe material <NUM>, and the metal pipe material <NUM> produces heat (Joule heat) due to the resistance present in the metal pipe material <NUM>. In this case, the measurement value of the thermocouple <NUM> is monitored always, and based on the results thereof, the energization is controlled and the cylinder unit <NUM> of the gas supply mechanism <NUM> is operated. Accordingly, both ends of the metal pipe material <NUM> are sealed by the sealing member <NUM>.

<FIG> is a diagram showing operations of the blow forming die and the upper die holder and a change in shape of the metal pipe material. <FIG> is a diagram following <FIG>. <FIG> is a diagram following <FIG>.

As shown in <FIG>, the blow forming die <NUM> is closed with respect to the metal pipe material <NUM> after heating. In this case, the protrusions 96b of the upper die holder <NUM> proceed into the spaces S1 and S2 of the lower die holder <NUM>, and between the recessed part <NUM> of the lower die <NUM> and the recessed part <NUM> of the upper die <NUM>, a main cavity part MC with a substantially rectangular cross-sectional shape is formed that is a gap for forming a pipe part (main body part) 100a. With this, sub-cavity parts SC1 and SC2 that communicate with the main cavity part MC and are gaps for forming flange parts 100b and 100c are respectively formed at both sides of the main cavity part MC between the upper end surface of the lower die <NUM> and the lower end surface of the upper die <NUM>.

Here, the sub-cavity parts SC1 and SC2 between the upper end surface of the lower die <NUM> and the lower end surface of the upper die <NUM> extend to be opened to the outside of the die. The sub-cavity parts SC1 and SC2 are blocked from the outside by inner surfaces 96f of the protrusions 96b of the upper die holder <NUM>. The protrusions 96b of the upper die holder <NUM>, blocking the sub-cavity parts SC1 and SC2 from the outside of the die, are operated such that foreign matter such as fragments generated when, for example, the metal pipe bursts in the die is prevented from advancing out of the die through the sub-cavity parts SC1 and SC2 and from being discharged. Accordingly, the upper die holder <NUM> having the protrusions 96b also functions as a shielding member.

In this state, that is, in a state before the blow forming die is completely closed, the metal pipe material <NUM> is fitted in the main cavity part MC. In a state in which the metal pipe material is in contact with the bottom surface of the recessed part <NUM> of the lower die <NUM> and the bottom surface of the recessed part <NUM> of the upper die <NUM>, a high-pressure gas is supplied into the metal pipe material <NUM> by the gas supply part <NUM> to start blow forming.

Here, since the metal pipe material <NUM> is softened by being heated at a high temperature (about <NUM>), the gas supplied into the metal pipe material <NUM> is thermally expanded. Therefore, for example, with the use of compressed air as a gas to be supplied, the metal pipe material <NUM> at <NUM> can be easily expanded by thermally expanded compressed air.

In parallel with this, the blow forming die <NUM> is further closed, and as shown in <FIG>, the main cavity part MC and the sub-cavity parts SC1 and SC2 are further narrowed between the lower die <NUM> and the upper die <NUM>.

Accordingly, the metal pipe material <NUM> is expanded in the main cavity part so as to follow the recessed parts <NUM> and <NUM>, and parts (both side parts) 14a and 14b of the metal pipe material <NUM> are expanded so as to enter into the sub-cavity parts SC1 and SC2, respectively.

As shown in <FIG>, the blow forming die <NUM> is further closed, and thus the lower end surface 96d of the protrusion 96b of the upper die holder <NUM> is brought into contact with the bottom surface 93d of the recessed part 93a of the lower die holder <NUM>, the step surface 96e of the upper die holder <NUM> is brought into contact with the upper end surface 93e of the protrusion 93b of the lower die holder <NUM>, and the inner surface of the protrusion 93b of the lower die holder <NUM> and the outer surface of the protrusion 96b of the upper die holder <NUM> are brought into contact with each other. In a state in which the lower die holder <NUM> and the upper die holder <NUM> are firmly adhered to each other, the closing of the blow forming die <NUM> is completed.

In this case, the main cavity part MC and the sub-cavity parts SC1 and SC2 are further narrowed than in the state shown in <FIG>, and in this state, the sub-cavity parts SC1 and SC2 are blocked from the outside by the inner surfaces 96f of the protrusions 96b of the upper die holder <NUM> as described above.

Accordingly, the metal pipe material <NUM> softened by heating and supplied with the high-pressure gas is formed as the pipe part 100a with a rectangular cross-sectional shape following the rectangular cross-sectional shape of the main cavity part MC in the main cavity part MC, and formed as the flange parts 100b and 100c with a rectangular cross-sectional shape in which a part of the metal pipe material <NUM> is folded in the sub-cavity parts SC1 and SC2.

In this blow forming, quenching is performed in such a way that the outer peripheral surface of the metal pipe material <NUM> expanded by being subjected to the blow forming is brought into contact with the recessed part <NUM> of the lower die <NUM> so as to be rapidly cooled, and simultaneously, brought into contact with the recessed part <NUM> of the upper die <NUM> so as to be rapidly cooled (since the upper die <NUM> and the lower die <NUM> have a large heat capacity and are managed at a low temperature, the heat of the pipe surface is taken to the dies at once in a case where the metal pipe material <NUM> is brought into contact with the dies. Such a cooling method is referred to as die contact cooling or die cooling. Immediately after the rapid cooling, the austenite is transformed to martensite (hereinafter, transformation of austenite to martensite will be referred to as martensite transformation). Since the cooling rate is reduced in the second half of the cooling, the martensite is transformed to another structure (troostite, sorbate, or the like) owing to recuperation. Therefore, there is no need to perform a separate tempering treatment. In this embodiment, in place of or in addition to the die cooling, a cooling medium may be supplied to the metal pipe <NUM> to perform cooling. For example, the metal pipe material <NUM> may be brought into contact with the die (upper die <NUM> and lower die <NUM>) to be cooled until the temperature is lowered to a temperature at which the martensite transformation starts, and then, the die may be opened and a cooling medium (gas for cooling) may be allowed to flow to the metal pipe material <NUM> to cause the martensite transformation.

By the above-described forming method, the metal pipe <NUM> having the pipe part 100a and the flange parts 100b and 100c can be obtained as a formed product as shown in <FIG>. In this embodiment, since the main cavity part MC is configured to have a rectangular cross-sectional shape, the metal pipe material <NUM> is subjected to the blow forming in accordance with the shape, and thus the pipe part 100a is formed into a rectangular cylindrical shape. The shape of the main cavity part MC is not particularly limited. In accordance with a desired shape, any shape may be employed such as a circular cross-sectional shape, an elliptical cross-sectional shape, or a polygonal cross-sectional shape.

According to this embodiment, in the expanding and forming of the metal pipe material <NUM> in the main cavity part MC and the sub-cavity parts SC1 and SC2 communicating with the main cavity part MC in the blow forming die <NUM>, in a case where the material itself has a low strength, and thus the metal pipe bursts due to the high-pressure gas and foreign matter such as fragments is generated in the blow forming die <NUM> (main cavity part SC or sub-cavity parts SC1 and SC2), foreign matter moving outward in the extending direction (horizontal direction in <FIG>) of the sub-cavity parts SC1 and SC2 crossing the extending direction of the metal pipe material <NUM> is prevented from advancing by the protrusions 96b of the upper die holder <NUM> that is a shielding member provided on the extending line of the sub-cavity parts SC1 and SC2 in the expanding of the metal pipe material <NUM> and brought into contact with the side surfaces of the upper die <NUM>. Accordingly, the foreign matter discharged from the main cavity part MC or the sub-cavity parts SC1 and SC2 can be securely prevented from scattering to the surroundings of the die without being discharged to the outside of the die.

In addition, the protrusion 96b of the upper die holder <NUM> is provided to be brought into contact with the side surface of the upper die <NUM>, and blocks the sub-cavity parts SC1 and SC2 formed between the lower die <NUM> and the upper die <NUM> from the extending direction of the sub-cavity parts SC1 and SC2 when being moved with the movement of the upper die <NUM> to close the blow forming die <NUM>. Accordingly, the upper die holder <NUM> functions as a shielding member and there is no need to provide a separate shielding member. In addition, in a state in which the upper die holder <NUM> serves as a shielding member and is released from the die, the upper die holder <NUM> is separated upward from the lower die <NUM> together with the upper die <NUM>. Accordingly, there is an advantage in that for example, in a case where the metal pipe material <NUM> is inserted into the lower die <NUM> or in a case where the formed metal pipe <NUM> is detached from the lower die <NUM>, the protrusion 96b of the upper die holder <NUM> does not become a hindrance. The upper die holder <NUM> having the protrusion 96b is used as a shielding member since it is used particularly effectively as described above. However, the upper die holder <NUM> may have no protrusion 96b and the lower die holder <NUM> may be provided with a protrusion that is brought into contact with the side surface of the lower die <NUM> and protrudes upward to function as a shielding member that blocks the sub-cavity parts SC1 and SC2 formed between the lower die <NUM> and the upper die <NUM> from the extending direction of the sub-cavity parts SC1 and SC2 in a case where the die is closed.

<FIG> is a schematic diagram showing a configuration of a main part of a forming device according to a second embodiment of the invention. The second embodiment is different from the first embodiment in that by using an upper die holder <NUM> having no protrusion 96b in place of the upper die holder <NUM> and using a lower die holder <NUM> having no protrusion 93b in place of the lower die holder <NUM>, the sub-cavity parts SC1 and SC2 are not blocked by the die holders <NUM> and <NUM> from the extending direction of the sub-cavity parts SC1 and SC2 in a case where the blow forming die <NUM> is closed, and shielding plates <NUM>, each constituting a shielding member, are provided at positions separated from the side surfaces of the die on the extending line of the sub-cavity parts SC1 and SC2, respectively.

The shielding plate <NUM> is provided with a lower shielding plate <NUM>, the length in an axial direction (length in a direction perpendicular to the plane of <FIG>) of which is almost the same as the length of the blow forming die <NUM> in the axial direction, that is erected on the lower die holder <NUM> and extends upward, and an upper shielding plate <NUM> that is erected on the upper die holder <NUM> and extends downward.

In a state before the blow forming is started, the upper die <NUM> is largely separated upward from the lower die <NUM> (see <FIG>). In this case, an upper part of the lower shielding plate <NUM> and a lower part of the upper shielding plate <NUM> does not overlap each other in a horizontal direction shown in the drawing, crossing the metal pipe material <NUM>. In a state shown in the drawing in which the upper die <NUM> is moved downward to start the blow forming, the upper part of the lower shielding plate <NUM> and the lower part of the upper shielding plate <NUM> overlap each other in the horizontal direction shown in the drawing, crossing the metal pipe material <NUM>, and the side surfaces thereof are brought into contact with each other. In this state in which the side surfaces are brought into contact with each other, in a case where the upper die <NUM> is further moved downward, the lower part of the upper shielding plate <NUM> is further moved downward while overlapping with the upper part of the lower shielding plate <NUM>.

According to the second embodiment, in the expanding and forming of the metal pipe material <NUM> in the main cavity part MC and the sub-cavity parts SC1 and SC2 communicating with the main cavity part MC in the blow forming die <NUM>, foreign matter such as fragments may be generated. In this case, the foreign matter moves outward in the extending direction of the sub-cavity parts SC1 and SC2 (horizontal direction in <FIG>). In addition, the foreign matter is prevented from advancing by the shielding plates <NUM> provided on the extending line of the sub-cavity parts SC1 and SC2 in the expanding of the metal pipe material <NUM> and separated from the side surfaces of the die. Accordingly, the foreign matter discharged from the main cavity part MC or the sub-cavity parts SC1 and SC2 can be prevented from scattering to the surroundings of the die, specifically, to a region outside the shielding plates <NUM>, and can be allowed to scatter only in a region inside the shielding plates <NUM> (region where no worker approaches during the operation).

<FIG> is a schematic diagram showing a configuration of a main part of a forming device according to a third embodiment of the invention. The third embodiment is different from the second embodiment in that shielding plates (shielding members) <NUM> having a lower shielding plate <NUM> and an upper shielding plate <NUM>, end parts of which are brought into contact with each other, are used in place of the shielding plates <NUM> having the lower shielding plate <NUM> and the upper shielding plate <NUM> overlapping each other.

The lower shielding plate <NUM> is biased upward by a compression coil spring <NUM> and supported movably up and down by the lower die holder <NUM>. The upper shielding plate <NUM> is biased downward by a compression coil spring <NUM> and supported movably up and down by the upper die holder <NUM>.

In a state before the blow forming is started, the upper die <NUM> is largely separated upward from the lower die <NUM> (see <FIG>) and an upper end part of the lower shielding plate <NUM> and a lower end part of the upper shielding plate <NUM> are separated from each other. However, in a state shown in the drawing in which the upper die <NUM> is moved downward to start the blow forming, a protrusion <NUM> of the upper end part of the lower shielding plate <NUM> proceeds into and firmly adheres to a recessed part <NUM> of the lower end part of the upper shielding plate <NUM>. Accordingly, even in a case where the upper die <NUM> and the upper shielding plate <NUM> are moved downward from the state shown in the drawing to close the blow forming die <NUM>, the compression coil springs <NUM> and <NUM> are compressed in the axial direction, and the state in which the protrusion <NUM> of the upper end part of the lower shielding plate <NUM> proceeds into and firmly adheres to the recessed part <NUM> of the lower end part of the upper shielding plate <NUM> is maintained.

According to the third embodiment, in the expanding and forming of the metal pipe material <NUM> in the main cavity part MC and the sub-cavity parts SC1 and SC2 communicating with the main cavity part MC in the blow forming die <NUM>, foreign matter such as fragments may be generated. In this case, the foreign matter moves outward in the extending direction of the sub-cavity parts SC1 and SC2 (horizontal direction in <FIG>). The foreign matter is prevented from advancing by the shielding plates <NUM> provided on the extending line of the sub-cavity parts SC1 and SC2 in the expanding of the metal pipe material <NUM> and separated from the side surfaces of the die. Accordingly, the foreign matter discharged from the main cavity part MC or the sub-cavity parts SC1 and SC2 can be prevented from scattering to the surroundings of the die, specifically, to a region outside the shielding plates <NUM>, and can be allowed to scatter only in a region inside the shielding plates <NUM> (region where no worker approaches during the operation).

In place of the shielding plates <NUM> and <NUM> of the second and third embodiments, a shielding member such as a shielding block may be disposed to block the sub-cavity parts SC1 and SC2 from the outside of the die (in a direction crossing the extending direction of the metal pipe material <NUM>) in a case where the block forming die <NUM> is closed. The shielding member such as a shielding block is provided at a position separated from the dies <NUM> and <NUM> so as not to block the sub-cavity parts SC1 and SC2 before closing of the die, and is moved to a position to block the sub-cavity parts SC1 and SC2 in a case where the die is closed. In addition, a part or the whole part of the shielding member such as a shielding block may proceed into the sub-cavity parts SC1 and SC2 to block the sub-cavity parts.

Claim 1:
A forming device (<NUM>) that expands a metal pipe material (<NUM>) to form a metal pipe (<NUM>), the device comprising:
an upper die (<NUM>) and a lower die (<NUM>) that form a main cavity part (MC) forming a main body part (100a) of the metal pipe (<NUM>) and a sub-cavity part (SC1, SC2) forming a flange part (100b, 100c) of the metal pipe (<NUM>) by surfaces thereof opposed to each other;
a shielding member (<NUM>, <NUM>) configured to prevent foreign matter discharged from the main cavity part (MC) or the sub-cavity part (SC1, SC2) from scattering;
a heating mechanism (<NUM>) configured to energize the metal pipe material (<NUM>) to heat the metal pipe material (<NUM>); and
a gas supply part (<NUM>) configured to supply a gas for expanding the metal pipe material (<NUM>) into the metal pipe material (<NUM>) held between the lower die (<NUM>) and the upper die (<NUM>) and heated by the heating mechanism (<NUM>),
characterized in that
the sub-cavity part (SC1, SC2) is extended to be opened to the outside of the die in a direction crossing an extending direction of the metal pipe material (<NUM>), and
the shielding member (<NUM>, <NUM>) is provided on a line in which the sub-cavity part (SC1, SC2) extends in the expanding of the metal pipe material (<NUM>).