Forming system

Abstract

This forming system for forming a metal pipe material comprises: a forming unit that supplies a fluid to the metal pipe material disposed in a forming die and performs forming; an internal pressure adjustment mechanism that adjusts the pressure inside the metal pipe material; and a mechanism that, at an emergency stop during forming, suppresses die opening of the forming die until the pressure inside the metal pipe material is reduced to a prescribed pressure by the internal pressure adjustment mechanism.

Description

Forming system

[0001] The present disclosure relates to a forming system.

[0002] Conventionally, as a forming system, the one described in Patent Document 1 is known. This forming system expands and forms a metal pipe material.

[0003] Japanese Patent Application Laid-Open No. 2009-220141

[0004] In the forming system in the above-mentioned Patent Document 1, an emergency stop may occur due to power interruption caused by an emergency stop or power interruption during a power failure. In this case, the power supply to the mechanism that applies pressure to the mold stops. On the other hand, an emergency stop may also occur when the pressure inside the metal pipe material is high. In this case, the mold may not be able to restrain the expansion based on the residual pressure in the metal pipe material. As a result, the metal pipe material may burst sometimes, so it has been required to improve safety when an emergency stop occurs.

[0005] One aspect of the present disclosure is made to solve such problems, and an object thereof is to provide a forming system capable of improving safety.

[0006] A forming system according to one aspect of the present disclosure is a forming system for forming a metal pipe material, including a forming part that performs forming by supplying a fluid to the metal pipe material arranged in a mold, an internal pressure adjustment mechanism that adjusts the pressure inside the metal pipe material, and a mechanism that suppresses the mold opening until the inside of the metal pipe material is reduced to a predetermined pressure by the internal pressure adjustment mechanism during an emergency stop during forming.

[0007] The molding system is equipped with an internal pressure adjustment mechanism that adjusts the internal pressure of the metal pipe material. Therefore, the internal pressure adjustment mechanism can reduce the residual pressure of the metal pipe material in the event of an emergency stop. Furthermore, the molding system is equipped with a mechanism that suppresses the opening of the molding die until the internal pressure of the metal pipe material is reduced to a predetermined pressure by the internal pressure adjustment mechanism in the event of an emergency stop during molding. Therefore, it is possible to suppress the opening of the molding die by being pushed by the expansion reaction force of the metal pipe material while the internal pressure adjustment mechanism is reducing the internal pressure of the metal pipe material. Therefore, it is possible to suppress the rupture of the metal pipe material due to expansion. Suppressing the rupture of the metal pipe material reduces the sound of the rupture for surrounding workers. In addition, suppressing the rupture of the metal pipe material can protect surrounding equipment such as sensors and suppress damage to the mold caused by the rupture of the metal pipe material. As a result, safety can be improved even in the event of an emergency stop.

[0008] The mechanism may be configured such that, in the event of an emergency stop, the pressure applied to the mold is greater than the upward force exerted on the mold due to expansion based on residual pressure within the metal pipe material. This allows the mold to restrain the expansion of the metal pipe material through the applied pressure. Therefore, it is possible to suppress the metal pipe material from rupturing due to expansion.

[0009] The molding system further includes a pressure reduction mechanism that reduces the pressure applied to the mold. The pressure reduction mechanism does not reduce the pressure during an emergency stop, and the rate at which the pressure reduction mechanism reduces the pressure may be greater than the rate at which the mechanism itself reduces the pressure. In this case, the pressure reduction mechanism can reduce the pressure on the mold after molding during normal molding, not during an emergency stop. Furthermore, the pressure reduction mechanism can reduce the pressure more quickly than the mechanism itself. Therefore, during normal molding, it is possible to quickly move on to the next molding stage.

[0010] In a molding system, during normal molding, the internal pressure adjustment mechanism and the pressure reduction mechanism may be electrically controlled so that the pressure applied to the mold after molding by the molding section is completed is greater than the upward force on the mold due to expansion based on the residual pressure in the metal pipe material. In this case, during normal molding, the pressure reduction mechanism can quickly reduce the pressure while maintaining the state in which the mold restrains the expansion of the metal pipe material with the applied pressure.

[0011] According to one embodiment of this disclosure, a molding system that can improve safety can be provided.

[0012] This is a schematic diagram showing a specific example of a molding apparatus included in the molding system according to this embodiment. This is a schematic diagram showing the hydraulic circuit of the molding system. This is a schematic diagram showing the internal pressure adjustment mechanism of the molding system. This is a schematic diagram showing the pressure reduction mechanism and safety mechanism. This is a schematic diagram showing the pressure reduction mechanism and safety mechanism. This is a schematic diagram showing the pressure reduction mechanism and safety mechanism. This is a graph showing the relationship between the operation of the molding system, the expansion reaction force due to high-pressure gas, the press load, and the amount of slide movement. This is a graph showing the relationship between the operation of the molding system, the expansion reaction force due to high-pressure gas, and the press load during an emergency stop. This is a schematic diagram showing the pressure relief circuit in a comparative example. This is a graph showing the relationship between the operation of the molding system, the expansion reaction force due to high-pressure gas, and the press load during an emergency stop when using the pressure relief circuit in a comparative example. This is a schematic diagram showing the pressure relief circuit in a modified example.

[0013] Preferred embodiments of this disclosure will be described below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0014] Figure 1 is a schematic diagram showing a specific example of a molding apparatus included in the molding system 100 according to this embodiment.

[0015] The molding system 100 is a system for manufacturing molded products by heating a metal pipe material and molding the heated metal pipe material with a mold. A pipe-shaped metal pipe material 40, as shown in Figure 1, is used as the base material for the molded product.

[0016] As shown in Figure 1, the molding system 100 includes a molding device 103 (molding unit). The molding device 103 is a device that forms a hollow metal pipe by supplying fluid to a metal pipe material 40 placed in a molding die 102. Here, the molding device 103 is installed on a horizontal plane. The molding device 103 includes a molding die 102, a drive mechanism 3, a holding unit 4, a heating unit 101, a fluid supply unit 6, a cooling unit 7, and a control unit 8. In this specification, the metal pipe material 40 refers to a hollow article before molding is completed in the molding device 103. The metal pipe material 40 may be a hardenable steel pipe material. In addition, the direction in which the metal pipe material 40 extends during molding is sometimes referred to as the "longitudinal direction," and the direction perpendicular to the longitudinal direction is sometimes referred to as the "width direction."

[0017] The molding die 102 is a mold for forming a metal pipe from a metal pipe material 40, and comprises a lower mold 11 and an upper mold 12 that face each other in the vertical direction. The lower mold 11 and the upper mold 12 are made of steel blocks. Each of the lower mold 11 and the upper mold 12 is provided with a recess in which the metal pipe material 40 is contained. When the lower mold 11 and the upper mold 12 are in close contact with each other (closed mold state), their respective recesses form a space of the target shape in which the metal pipe material is to be formed. Therefore, the surface of each recess becomes the molding surface of the molding die 102. The lower mold 11 is fixed to the base 13 via a die holder or the like. The upper mold 12 is fixed to the slide of the drive mechanism 3 via a die holder or the like.

[0018] The drive mechanism 3 is a mechanism for moving at least one of the lower mold 11 and the upper mold 12. In Figure 1, the drive mechanism 3 has a configuration that moves only the upper mold 12. The drive mechanism 3 includes a slide 21 that moves the upper mold 12 so that the lower mold 11 and the upper mold 12 come into contact with each other, a pull-back cylinder 22 as an actuator that generates a force to pull the slide 21 upward, a main cylinder 23 as a drive source that pressurizes the slide 21 downward, and a drive source 24 that provides driving force to the main cylinder 23.

[0019] The holding part 4 is a mechanism for holding a metal pipe material 40 positioned between the lower mold 11 and the upper mold 12. The holding part 4 comprises a lower electrode 26 and an upper electrode 27 that hold the metal pipe material 40 at one end in the longitudinal direction of the molding die 102, and a lower electrode 26 and an upper electrode 27 that hold the metal pipe material 40 at the other end in the longitudinal direction of the molding die 102. The lower electrode 26 and the upper electrode 27 on both sides in the longitudinal direction hold the metal pipe material 40 by clamping the vicinity of the end of the metal pipe material 40 from above and below. Grooves having a shape corresponding to the outer circumferential surface of the metal pipe material 40 are formed on the upper surface of the lower electrode 26 and the lower surface of the upper electrode 27. The lower electrode 26 and the upper electrode 27 are provided with a drive mechanism (not shown) that allows them to move independently in the vertical direction.

[0020] The heating unit 101 heats the metal pipe material 40. The heating unit 101 is a mechanism that heats the metal pipe material 40 by passing an electric current through it. The heating unit 101 heats the metal material by passing an electric current through it. By passing an electric current through the metal pipe material 40, the heating unit 101 causes the metal material itself to generate heat through Joule heating due to its own electrical resistance (electric heating). The molding apparatus 103 is an apparatus that molds the metal material heated by the heating unit 101 using a molding die 102. The heating unit 101 heats the metal pipe material 40 in a state where it is separated from the lower mold 11 and the upper mold 12, between the lower mold 11 and the upper mold 12. The heating unit 101 is equipped with the lower electrodes 26 and upper electrodes 27 on both sides in the longitudinal direction as described above, and a power supply 28 that supplies power to the electrodes 26. The heating unit 101 is heated by energizing it using power supplied from the power supply 28.

[0021] Here, the state in which the metal pipe material 40 is positioned inside the molding die 102 is the state in which the metal pipe material 40 is positioned in the space between the upper mold 12 and the lower mold 11, which are facing each other. In this state, the metal pipe material 40 faces the upper mold 12 with a downward separation from the upper mold 12, and faces the lower mold 11 with an upward separation from the lower mold 11.

[0022] The fluid supply unit 6 is a mechanism for supplying high-pressure fluid into the metal pipe material 40 held between the lower mold 11 and the upper mold 12. The fluid supply unit 6 supplies high-pressure fluid to the metal pipe material 40, which has become hot due to heating in the heating unit 101, causing the metal pipe material 40 to expand. The fluid supply unit 6 is provided on both ends in the longitudinal direction of the molding die 102. The fluid supply unit 6 includes a nozzle 31 that supplies fluid into the metal pipe material 40 from an opening at the end of the metal pipe material 40, a drive mechanism 32 that moves the nozzle 31 back and forth relative to the opening of the metal pipe material 40, and a supply source 33 that supplies high-pressure fluid into the metal pipe material 40 via the nozzle 31. The drive mechanism 32 ensures a tight seal when supplying and exhausting fluid by making the nozzle 31 tightly attached to the end of the metal pipe material 40, and separates the nozzle 31 from the end of the metal pipe material 40 at other times. The fluid supply unit 6 may supply gases such as high-pressure air or inert gas as the fluid. Furthermore, the fluid supply unit 6 may be part of the same device as the heating unit 101, together with the holding unit 4 which has a mechanism for moving the metal pipe material 40 vertically.

[0023] The cooling unit 7 is a mechanism for cooling the mold 102. By cooling the mold 102, the cooling unit 7 can rapidly cool the expanded metal pipe material 40 when it comes into contact with the molding surface of the mold 102. The cooling unit 7 includes a flow path 36 formed inside the lower mold 11 and the upper mold 12, and a water circulation mechanism 37 that supplies and circulates cooling water to the flow path 36.

[0024] Thus, the mold 102 is provided with a hardening mechanism 105 for hardening the molded product 140. The hardening mechanism 105 consists of the molding surface of the mold 102 and the cooling section 7.

[0025] The control unit 8 is a device that controls the entire molding apparatus 103. The control unit 8 controls the drive mechanism 3, the holding unit 4, the heating unit 101, the fluid supply unit 6, and the cooling unit 7. The control unit 8 repeatedly performs the operation of molding the metal pipe material 40 with the molding die 102.

[0026] The control unit 8 controls the drive mechanism 3 to lower the upper mold 12 and bring it close to the lower mold 11, thereby closing the mold 102. Meanwhile, the control unit 8 controls the fluid supply unit 6 to seal the openings at both ends of the metal pipe material 40 with the nozzle 31 and supply fluid. As a result, the metal pipe material 40, which has been softened by heating, expands and comes into contact with the molding surface of the mold 102. The metal pipe material 40 is then formed to conform to the shape of the molding surface of the mold 102. When forming a metal pipe with a flange, a portion of the metal pipe material 40 is inserted into the gap between the lower mold 11 and the upper mold 12, and then the mold is closed to crush the inserted portion and form the flange. When the metal pipe material 40 comes into contact with the molding surface, it is rapidly cooled by the mold 102 cooled by the cooling unit 7, thereby quenching the metal pipe material 40.

[0027] In conventional press working, moving the mold in the pressurizing direction generates a load. In contrast, in the molding system 100 according to this embodiment, expansion molding is performed, so when high-pressure fluid is supplied to the metal pipe material 40, the metal pipe material 40 inside the mold 102 expands spontaneously. Therefore, when high-pressure fluid is supplied to the inside of the metal pipe material 40, the reaction force from the metal pipe material 40 increases rapidly. For this reason, the control unit 8 controls the molding system 102 so that it is not pushed back even when it receives a reaction force from the metal pipe material 40. Furthermore, when an emergency stop state occurs during molding, power is not supplied to each component in the molding apparatus 103. Even in such a case, the molding system 100 according to this embodiment can suppress mold opening caused by the molding system 102 being pushed back, even when it receives a reaction force due to the expansion of the metal pipe material 40. The configuration for performing such control will be explained with reference to Figures 2 and 3. Note that the emergency stop includes stopping the molding apparatus 103 by cutting off the power and control power supply of the molding system 100 when an emergency stop command is issued for a predetermined reason. Furthermore, an emergency stop also includes the stopping of the molding apparatus 103 due to the forcible interruption of power and control power supply, such as a power outage, even when an emergency stop command is not actively issued. In contrast, in this specification, "normal operation" means a state in which no emergency stop as described above has occurred and the molding apparatus 103 is performing molding according to predetermined operations.

[0028] As shown in Figure 2, the molding system 100 is a configuration example that includes a hydraulic circuit 115 for operating the mold 102 of the molding apparatus 103. The hydraulic circuit 115 functions as the drive source 24 (see Figure 1) described above. The hydraulic circuit 115 includes hydraulic pumps 50 and 51, a hydraulic oil tank 52, a hydraulic circuit 56 for the return cylinder, a hydraulic circuit 57 for auxiliary equipment control, and a pressure relief circuit 60. The electrical equipment of the hydraulic circuit 115 is electrically controlled by the control unit 8.

[0029] The hydraulic pump 50 is a servo motor type pump that supplies hydraulic fluid to the main cylinder 23. The hydraulic pump 50 is installed on the line L1 that connects the hydraulic fluid tank 52 and the main cylinder 23. The hydraulic pump 50 supplies hydraulic fluid from the hydraulic fluid tank 52 to the main cylinder 23 via the line L1. When the hydraulic pump 50 supplies hydraulic fluid to the oil chamber 23a of the main cylinder 23, the main cylinder 23 applies downward pressure to the upper mold 12. As a result, the upper mold 12 is lowered and the molding die 102 is closed.

[0030] The hydraulic pump 51 is located on line L2, which connects the hydraulic oil tank 52 to the hydraulic circuit 56 for the return cylinder and the hydraulic circuit 57 for controlling auxiliary equipment. The hydraulic pump 51 supplies hydraulic oil from the hydraulic oil tank 52 to the hydraulic circuit 56 for the return cylinder and the hydraulic circuit 57 for controlling auxiliary equipment via line L2. The hydraulic circuit 56 for the return cylinder is a hydraulic circuit that supplies hydraulic oil to the return cylinder 22 at predetermined timings. The hydraulic circuit 57 for controlling auxiliary equipment is a hydraulic circuit that supplies hydraulic oil to the auxiliary equipment at predetermined timings.

[0031] The pressure relief circuit 60 releases the operating hydraulic pressure from the oil chamber 23a of the main cylinder 23, thereby releasing the pressurizing force on the mold 102 and releasing the molding energy. The pressure relief circuit 60 returns the hydraulic fluid to the hydraulic fluid tank 52 via lines L3 and L4 connected to line L1. After the pressure relief circuit 60 has relieved the pressure from the main cylinder 23, the hydraulic circuit 56 for the pull-back cylinder controls the pull-back cylinder 22 to pull back the upper mold 12. This causes the mold 102 to open. Further details of the pressure relief circuit 60 will be described later.

[0032] As shown in Figure 3, the molding system 100 includes an internal pressure adjustment mechanism 106 that adjusts the internal pressure of the metal pipe material 40. The internal pressure adjustment mechanism 106 functions as the supply source 33 described above in Figure 1. The internal pressure adjustment mechanism 106 includes a high-pressure gas generator 80, a high-pressure gas control device 81, supply valves 82A and 82B, and discharge valves 83A and 83B. The electrical equipment of the internal pressure adjustment mechanism 106 is electrically controlled by the control unit 8.

[0033] The high-pressure gas generator 80 is a device that takes in air and generates high-pressure gas. The high-pressure gas control device 81 is a device that controls the high-pressure gas generated by the high-pressure gas generator 80. The high-pressure gas control device 81 includes a control valve 81a that controls the supply of high-pressure gas and a pressure storage tank 81b that stores the high-pressure gas. The high-pressure gas control device 81 is connected to the right supply valve 82A via line L11. The high-pressure gas control device 81 is connected to the left supply valve 82B via line L12.

[0034] The supply valves 82A and 82B are valves that switch between supplying and stopping the supply of high-pressure gas to the metal pipe material 40 by opening and closing them. The right supply valve 82A is connected to the right nozzle 31 via line L13. The left supply valve 82B is connected to the left nozzle 31 via line L14. The discharge valves 83A and 83B are valves that switch between discharging and stopping the discharge of high-pressure gas from the metal pipe material 40 by opening and closing them. The right discharge valve 83A is connected to the right supply valve 82A via line L16. The left discharge valve 83B is connected to the left supply valve 82B via line L17. The left and right discharge valves 83A and 83B are connected to the discharge line L18. Separate discharge lines may be installed on the right and left sides as the discharge line L18.

[0035] The control unit 8 (see Figure 1) closes the left and right discharge valves 83A and 83B, supplies high-pressure gas from the high-pressure gas control device 81, and opens the left and right supply valves 82A and 82B to fill the inside of the metal pipe material 40 with high-pressure gas through lines L11, L12, L13, L14 and the left and right nozzles 31. By using the expansion force of this high-pressure gas in combination with the closure of the mold 102 controlled by the hydraulic circuit 115 in Figure 2, expansion molding is performed.

[0036] When molding is complete, the control unit 8 stops supplying high-pressure gas from the high-pressure gas control device 81. The control unit 8 closes the left and right supply valves 82A and 82B, opens the left and right discharge valves 83A and 83B, and discharges the high-pressure gas that has been supplied to the inside of the molded product into the atmosphere using lines L13, L14, L16, L17, and L18, thereby releasing the expansion force.

[0037] Here, normally closed valves are used as the left and right supply valves 82A and 82B, and normally open valves are used as the left and right discharge valves 83A and 83B. Normally closed means that the valve automatically closes mechanically when the power supply to the valve is stopped. Normally open means that the valve automatically opens mechanically when the power supply to the valve is stopped. In the event of an emergency stop, the supply valves 82A and 82B close and the discharge valves 83A and 83B open. As a result, the internal pressure adjustment mechanism 106 automatically stops the supply of high-pressure gas and releases the energy inside the molded product by releasing the high-pressure gas inside the molded product.

[0038] Next, the detailed configuration of the pressure relief circuit 60 will be described with reference to Figures 4 to 6. As shown in Figures 4 to 6, the pressure relief circuit 60 is an example of a circuit that includes a safety mechanism 61 (mechanism) and a pressure reduction mechanism 62. The pressure relief circuit 60 also includes the aforementioned lines L3 and L4, and lines L21, L22, L23, and L24. Lines L21, L22, and L23 branch off from line L3 at branching point P1. Lines L21 and L23 merge at merging point P3. Line L22, line L24 extending from merging point P3, and line L4 merge at merging point P2.

[0039] The safety mechanism 61 is a mechanism that suppresses the opening of the mold 102 in the event of an emergency stop during molding until the internal pressure of the metal pipe material 40 is reduced to a predetermined pressure by the internal pressure adjustment mechanism 106. Details of the pressure relationship will be described later. The safety mechanism 61 is equipped with a switching valve 61a provided on line L21. A normally open valve is used as the switching valve 61a. During normal pressurization of the mold, the switching valve 61a is in a closed state (see Figure 4). During normal pressure release after molding is complete, the switching valve 61a is in a closed state (see Figure 5). In the event of an emergency stop, the switching valve 61a opens due to the cessation of power supply (see Figure 6). The switching valve 61a is also configured as a valve that performs low-speed pressure release by keeping the flow rate of hydraulic fluid low. A safety valve 63 is provided on line L23.

[0040] The pressure reduction mechanism 62 is a mechanism that reduces the pressure applied to the mold 102 by releasing pressure. The pressure reduction mechanism 62 reduces the pressure after molding is completed under normal circumstances. The pressure reduction mechanism 62 does not reduce the pressure during an emergency stop. The pressure reduction mechanism 62 comprises line L30, a switching valve 62a provided on line L30, and an on-off valve 62b provided on line L22. Line L30 branches off from line L3 at branching point P4 and is connected to the on-off valve 62b. The pressure reduction mechanism 62, through the combination of the switching valve 62a and the on-off valve 62b, constitutes a normally closed valve. A normally open valve is used as the switching valve 62a. When the switching valve 62a is open, the on-off valve 62b is closed by the pressure of the hydraulic fluid supplied via line L30. When the switching valve 62a is closed, the on-off valve 62b is not affected by the pressure of the hydraulic fluid via line L30 and remains open. During normal pressurization of the molding die, the switching valve 62a is open and the on-off valve 62b is closed (see Figure 4). During normal pressure relief after molding is complete, the switching valve 62a is closed and the on-off valve 62b is open (see Figure 5). In the event of an emergency stop, the switching valve 62a opens and the on-off valve 62b automatically closes when the power supply is cut off (see Figure 6). The pressure reduction mechanism 62 is configured as a valve that performs high-speed pressure relief by allowing a large flow rate of hydraulic fluid to flow through it. The flow rate of hydraulic fluid that the pressure reduction mechanism 62 can flow is greater than the flow rate of the safety mechanism 61. As a result, the speed at which the pressure reduction mechanism 62 reduces the pressure is greater than the speed at which the safety mechanism 61 reduces the pressure.

[0041] As described above, as shown in Figure 4, during normal pressurization of the mold, hydraulic fluid is supplied from the hydraulic pump 50 to the main cylinder 23 via line L1. At this time, the hydraulic fluid flows to the pressure relief circuit 60 side via line L3. However, since both the safety mechanism 61 and the pressurization pressure reduction mechanism 62 are closed, the hydraulic fluid is stopped by valves 61a, 62b, and 63 in lines L21, L22, and L23, respectively. Therefore, the hydraulic fluid does not flow to the hydraulic fluid tank 52. As a result, no pressure relief occurs, and the pressurization pressure of the main cylinder 23 on the mold 102 is not reduced.

[0042] As shown in FIG. 5, during normal punching after molding is completed, the supply of hydraulic oil from the hydraulic pump 50 to the main cylinder 23 via the line L1 is stopped. Therefore, the line L1 is in a state where high-pressure hydraulic oil exists. At this time, the safety mechanism 61 is closed, and the pressure reduction mechanism 62 is in an open state. Therefore, the hydraulic oil is discharged to the hydraulic oil tank 52 via the line L3, the line L22, and the line L4. Therefore, high-speed punching is performed by the pressure reduction mechanism 62, and the pressure applied to the mold 102 of the main cylinder 23 is rapidly reduced.

[0043] As shown in FIG. 6, during an emergency stop, the supply of hydraulic oil from the hydraulic pump 50 to the main cylinder 23 via the line L1 is stopped. Therefore, the line L1 is in a state where high-pressure hydraulic oil exists. At this time, the pressure reduction mechanism is automatically closed, and the safety mechanism 61 is automatically in an open state. Therefore, the hydraulic oil is discharged to the hydraulic oil tank 52 via the line L3, the line L2

[0043] , the line L2 , and the line L4. Therefore, low-speed punching is performed by the safety mechanism 61, and the pressure applied to the mold 102 of the main cylinder 23 is slowly reduced.

[0044] Next, referring to FIG. 7, the operation of the molding system 100 during normal times will be described. FIG. 7 is a graph showing the relationship between the operation of the molding system 100, the expansion reaction force by high-pressure gas, the press load, and the slide movement amount. The expansion reaction force by high-pressure gas is the reaction force that the metal pipe material 40 can apply to the mold 102 due to the presence of high-pressure gas inside the metal pipe material 40. The press load is the load acting on the upper mold 12 due to the pressure applied by the main cylinder 23 to the upper mold 12. The slide movement amount is the movement amount of the slide 21 and indicates the position of the upper mold 12

[0044] .

[0045] Figure 7 shows the process of operations performed by the molding system 100 in chronological order. "Approach" is the process of lowering the upper mold 12 to a position where electrical heating can be performed. "Electrical heating" is the process of heating the metal pipe material 40 in the heating section 101. "Primary blow position movement" is the process of moving the upper mold 12 to the primary blow position. "Primary blow" is the process of expanding the metal pipe material 40 while the molding die 102 is not completely closed, and shaping the metal pipe material 40 to conform to the molding die 102. "Secondary blow position movement" is the process of molding the metal pipe material 40 into the product shape while the molding die 102 is completely closed. "Pipe internal pressure exhaust" is the process of exhausting the high-pressure fluid inside the molded product after molding. "Press load release" is the process of releasing the pressure applied to the molding die 102. "Rising" is the process of raising the upper mold 12 back to its original position before molding. The processes of "primary blow position movement," "primary blow," and "secondary blow position movement" are in a section where the mold 102 is closed but not completely sealed, known as "upper and lower mold non-sealed." The processes of "secondary blow" and "pipe internal pressure exhaust" are in a section where the mold 102 is completely sealed, known as "upper and lower mold sealed." Of these processes, the period from time t1 when the primary blow starts to time t2 when the secondary blow is completed is considered to be the time when molding is being performed by the molding device 103. Therefore, time t2 is considered to be the time when molding is completed.

[0046] During normal molding, the hydraulic circuit 115 is in a pressurized state as shown in Figure 4 before the molding is completed. Also, during normal molding, after the molding is completed by the molding device 103 at time t2, the control unit 8 electrically controls the internal pressure adjustment mechanism 106 and the pressurizing pressure reduction mechanism 62 so that the pressurizing pressure (press load) applied to the mold 102 is greater than the upward force (expansion reaction force) of the mold 102 due to the expansion caused by the residual pressure inside the metal pipe material 40. Specifically, when the molding is completed at time t2, the control unit 8 controls the internal pressure adjustment mechanism 106 to discharge the high-pressure gas inside the metal pipe material 40. As a result, the expansion reaction force due to the residual pressure decreases at a constant rate and drops to the value at atmospheric pressure at time t3 (see G1 in Figure 7). The control unit 8 maintains the press load by not releasing pressure using the pressurizing pressure reduction mechanism 62 until time t3 (see G2 in Figure 7). As a result, the control unit 8 maintains a state in which the press load is greater than the expansion reaction force. Then, at time t3, the control unit 8 starts depressurizing using the pressure reduction mechanism 62. As a result, the press load decreases at a constant rate (see G3 in Figure 7). Since the reduction of the expansion reaction force is complete, the control unit 8 maintains a state in which the press load is greater than the expansion reaction force.

[0047] Next, with reference to Figure 8, the operation of the molding system 100 during an emergency stop will be explained. Figure 8 is a graph showing the relationship between the operation of the molding system 100, the expansion reaction force due to high-pressure gas, and the press load. As shown in Figure 8, the operation is the same as in the normal operation shown in Figure 7 up to the middle of the secondary blowing.

[0048] Here, assume that an emergency stop is made at time t2x during the secondary blow, and the power supply to the molding device 103 is cut off. Therefore, the control signal from the control unit 8 is stopped. At this time, the internal pressure adjustment mechanism 106 automatically discharges the high-pressure gas inside the metal pipe material 40 mechanically. As a result, the expansion reaction force due to the residual pressure decreases at a constant reduction rate and drops to the value at atmospheric pressure at time t3x (see G1x in FIG. 8). Note that the reduction rate of the expansion reaction force (gradient of G1x) by the internal pressure adjustment mechanism 106 at this time is the same as the reduction rate (gradient of G1) shown in FIG. 7. At time t2x during the emergency stop, the safety mechanism 61 immediately starts the pressure relief mechanically and automatically. As a result, the press load decreases at a constant reduction rate (see G3x in FIG. 8). The reduction rate of the press load (gradient of G3x) at this time is smaller than the reduction rate (see G3) shown in FIG. 7 and also smaller than the reduction rate of the expansion reaction force (gradient of G1x) by the internal pressure adjustment mechanism 106. Therefore, until time t3x, the state where the press load is greater than the expansion reaction force is maintained. From the above, during an emergency stop during molding, the safety mechanism 61 can suppress the mold opening of the mold 102 until the inside of the metal pipe material 40 is reduced to a predetermined pressure (here, atmospheric pressure) by the internal pressure adjustment mechanism 106. Also, the safety mechanism 61 is configured such that the pressing force applied to the mold during an emergency stop is greater than the upward pushing force of the mold 102 due to the expansion based on the residual pressure in the metal pipe material 40.

[0049] When discharging the high-pressure gas to release the expansion reaction force of the high-pressure gas, the volume of the high-pressure gas expands during exhaust. For example, when injecting a high-pressure gas of 28 MPa into the pipe, during exhaust, the total volume of the volume inside the molded product and the volume inside the vent pipe expands about 280 times. Therefore, it may take several seconds for exhaust. In order to shorten the exhaust time, during normal molding, depending on the shape of the molded product, if the press load is released at a speed slower than this exhaust speed, the productivity is poor. Therefore, by using the pressure reduction mechanism 62 to perform a high-speed pressure relief of normal close, the productivity can be increased.

[0050] Next, the operation and effects of the molding system 100 according to the present embodiment will be described.

[0051] The molding system 100 according to this embodiment includes an internal pressure adjustment mechanism 106 that adjusts the internal pressure of the metal pipe material 40. Therefore, the internal pressure adjustment mechanism 106 can reduce the residual pressure of the metal pipe material 40 in the event of an emergency stop.

[0052] Here, a molding system relating to a comparative example will be described with reference to Figures 9 and 10. The depressurization circuit 60 of the molding system 200 shown in Figure 9 is an example of a general hydraulic press depressurization circuit, having a configuration in which the safety mechanism 61 is omitted from the depressurization circuit 60 shown in Figure 4. In the comparative example, the pressure reduction mechanism 62 performs depressurization during normal operation and during emergency stops.

[0053] As shown in Figure 10, at time t2x during an emergency stop, the pressure reduction mechanism 62 immediately and automatically begins to release pressure at high speed. As a result, the press load decreases at a constant rate (see G3y in Figure 10). The rate at which the press load decreases at this time (the gradient of G3y) is greater than the rate at which the expansion reaction force decreases due to the internal pressure adjustment mechanism 106 (the gradient of G1y). Therefore, at point "A" in the figure, the expansion reaction force becomes greater than the press load. Consequently, at the moment when the difference between the expansion reaction force and the press load becomes large, there is a possibility that the metal pipe material 40 will expand, lifting the upper mold 12 and causing it to burst.

[0054] In contrast, the molding system 100 according to this embodiment further includes a safety mechanism 61 that suppresses the opening of the mold 102 until the internal pressure of the metal pipe material 40 is reduced to a predetermined pressure by the internal pressure adjustment mechanism 106 during an emergency stop during molding. Therefore, it is possible to suppress the opening of the mold 102 by being pushed by the expansion reaction force of the metal pipe material 40 while the internal pressure adjustment mechanism 106 is reducing the internal pressure of the metal pipe material 40. As a result, it is possible to suppress the metal pipe material 40 from bursting due to expansion. Suppressing the bursting of the metal pipe material 40 reduces the sound of the burst for surrounding workers. Furthermore, suppressing the bursting of the metal pipe material 40 protects surrounding equipment such as sensors and suppresses damage to the mold caused by the bursting of the metal pipe material 40. As a result, safety can be improved even during an emergency stop.

[0055] The safety mechanism 61 may be configured such that, in the event of an emergency stop, the pressurizing force applied to the mold 102 is greater than the upward force exerted on the mold 102 due to expansion based on the residual pressure within the metal pipe material 40. This allows the mold 102 to restrain the expansion of the metal pipe material 40 by the applied pressure. Therefore, it is possible to suppress the metal pipe material 40 from rupturing due to expansion.

[0056] The molding system 100 further includes a pressure reduction mechanism 62 that rapidly reduces the pressure applied to the mold 102. The pressure reduction mechanism 62 does not reduce the pressure during an emergency stop, and the speed at which the pressure reduction mechanism 62 reduces the pressure may be greater than the speed at which the safety mechanism 61 reduces the pressure. In this case, the pressure reduction mechanism 62 can reduce the pressure on the mold 102 after molding during normal molding, not during an emergency stop. Furthermore, the pressure reduction mechanism 62 can reduce the pressure more quickly than the safety mechanism 61. Therefore, during normal molding, it is possible to quickly move on to the next molding.

[0057] During normal molding, the molding system 100 may electrically control the internal pressure adjustment mechanism 106 and the pressure reduction mechanism 62 so that the pressure applied to the mold 102 after molding by the molding device 103 is completed is greater than the upward force on the mold 102 due to expansion based on the residual pressure in the metal pipe material 40. In this case, during normal molding, the pressure reduction mechanism 62 can quickly reduce the pressure while maintaining the state in which the mold 102 restrains the expansion of the metal pipe material 40 by the pressure.

[0058] This disclosure is not limited to the embodiments described above.

[0059] For example, the pressure relief circuit 60 shown in Figure 11 may be used. The pressure relief circuit 60 shown in Figure 11 does not have a pressure reduction mechanism 62, but only a safety mechanism 61. In this case, the safety mechanism 61 performs normal pressure relief and pressure relief during emergency stops. In the modified example shown in Figure 11, normal pressure relief takes time, so by adopting the configuration shown in Figure 4, pressure relief can be performed quickly by the pressure reduction mechanism 62.

[0060] For example, the molding apparatus shown in Figure 1 is merely an example, and the molding apparatus may have any configuration as long as it does not deviate from the spirit of this disclosure.

[0061] For example, the heating unit 101 does not necessarily have to be incorporated into the molding apparatus 103; the metal pipe material 40 may be heated outside the molding die, and the heated metal pipe material 40 may be placed into the molding die.

[0062] 40...Metal pipe material, 61...Safety mechanism, 62...Pressure reduction mechanism, 100...Molding system, 103...Molding device (molding section), 106...Internal pressure adjustment mechanism.

Claims

1. A molding system for forming a metal pipe material, comprising: a molding unit that performs molding by supplying fluid to the metal pipe material placed in a molding die; an internal pressure adjustment mechanism that adjusts the internal pressure of the metal pipe material; and a mechanism that, in the event of an emergency stop during molding, suppresses the opening of the molding die until the internal pressure of the metal pipe material is reduced to a predetermined pressure by the internal pressure adjustment mechanism.

2. The molding system according to claim 1, wherein the mechanism is configured such that, in the event of an emergency stop, the pressing force applied to the mold is greater than the upward force on the mold due to expansion based on the residual pressure in the metal pipe material.

3. The molding system according to claim 2, further comprising a pressure reduction mechanism for reducing the pressure applied to the molding die, wherein the pressure reduction mechanism does not reduce the pressure in the event of an emergency stop, and the rate at which the pressure reduction mechanism reduces the pressure is greater than the rate at which the mechanism reduces the pressure.

4. The molding system according to claim 3, wherein, during normal molding, the internal pressure adjustment mechanism and the pressure reduction mechanism are electrically controlled so that, after molding by the molding unit is completed, the pressure applied to the mold is greater than the upward force on the mold due to expansion based on the residual pressure in the metal pipe material.

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