JP6768351B2 - Press brake and bending method - Google Patents

Description

The present invention relates to a press brake and a bending method.

Conventionally, a press brake has been used as a device for bending a plate-shaped workpiece. A punch and a die are attached to the press brake, and a plate-shaped work is bent by the cooperation of the punch and the die (see, for example, Patent Document 1).
The press brake shown in Patent Document 1 includes a lower table on which a die is mounted, an upper table on which a punch is mounted, an elevating cylinder for raising and lowering the upper table, and pressure oil in the upper hydraulic chamber and the lower hydraulic chamber of the elevating cylinder. A bidirectional piston pump is provided to supply the oil. The bidirectional piston pump has a swash plate that is inclined with respect to the pump rotation axis.

Then, by tilting the swash plate between the two positions, the pump discharge flow rate is reduced in the region set for bending the work, and the pump discharge flow rate is increased in the other regions. Is being controlled.
Further, the press speed is improved by reducing the ascending / descending speed of the upper table in the region set for bending and changing the speed so as to be high in the other regions.

Japanese Unexamined Patent Publication No. 2014-779787

However, in the press brake shown in Patent Document 1, since the swash plate is tilted between two positions to change the discharge amount of the pump, the pressure is constant at each position, but the swash plate is Pressure fluctuations occur while moving from one position to the other. Since this pressure fluctuation occurs when the speed changes, it is difficult to operate the upper table stably. In addition, control for tilting the swash plate is also required, which complicates control.

An object of the present invention is to provide a press brake and a bending method capable of stably operating by simple control.

The press brake of the first invention is a press brake that bends a plate-shaped member by a punch and a die, and includes a movable table, a fixed table, a hydraulic cylinder, and a pump. A punch is attached to the movable table. A die is attached to the fixed table. The hydraulic cylinder has a first extension chamber and a second extension chamber to which oil is supplied when extending, and a contraction chamber to which oil is supplied when contracting. The hydraulic cylinder expands and contracts to bring the movable table closer to or further from the fixed table. The pump has a first discharge portion connected to the first extension chamber and the second extension chamber, and a second discharge portion connected to the contraction chamber, and is one of the first discharge portion and the second discharge portion. When discharging oil from the other side, the oil is sucked from the other side.

As described above, a hydraulic cylinder and a bidirectional pump having two first extension chambers and a second extension chamber are provided. When the movable table is brought close to the fixed table in an area other than the processing setting area set for bending the work, the oil from the pump is not supplied to the first extension chamber but to the second extension chamber. By supplying only the oil pressure, the area affected by the hydraulic pressure when the hydraulic cylinder is extended can be reduced. Therefore, the movable table can be brought close to the fixed table at high speed in an area other than the machining setting area. A region other than the machining setting region in such an approach can be said to be a high-speed approach region.

Further, by supplying oil to the first extension chamber, oil is supplied to both the first extension chamber and the second extension chamber in the machining setting area, and the hydraulic pressure acts when the hydraulic cylinder is extended. The area to be used can be increased. Therefore, the movable table can be brought closer to the fixed table by increasing the pressing force at a low speed in the machining setting area. The machining setting region in such an approach can be said to be a low-speed approach region.

That is, the approach speed of the variable table to the fixed table is changed from high speed to low speed only by changing the state in which oil is supplied to only one of the two extension chambers to the state in which oil is supplied to both extension chambers. Since the pressurizing pressure can be increased, it is possible to operate the movable table with the same efficiency without using a complicated bidirectional pump and system to make the discharge amount variable.

Further, the machining setting region (low-speed approach region) may be an region where the die and the punch actually come into contact with the work and the plate-shaped member is bent, or the die and the punch actually come into contact with the work. It may be set to a region including a region where the plate-shaped member is bent.
The press brake of the second invention is the press brake of the first invention, and further includes a resistance generating portion that generates resistance to the discharge of oil from the hydraulic cylinder due to the lowering of the movable table.

As a result, when the movable table is lowered, a counter force can be generated against the lowering due to its own weight. Therefore, it is possible to control the descent of the movable table by the oil discharged from the pump. If a counter force is not generated against the descent due to its own weight, it will be controlled by a negative torque when the movable table is descended, and it will easily become unstable due to the difference in viscosity due to the temperature change of the hydraulic oil, and the speed will be increased or accelerated. It was difficult to speed up. However, by generating a counter force, it is possible to control the lowering of the movable table with a positive torque due to hydraulic pressure. That is, the rotation speed and torque of the motor that operates the pump directly affect the operation of the movable table, and stable and fast operation of the movable table becomes possible.

The press brake of the third invention is the press brake of the second invention, in which the resistance generating portion is connected to the contraction chamber, shuts off oil when the hydraulic pressure is smaller than a predetermined value, and the hydraulic pressure is equal to or higher than a predetermined value. It has a valve that allows oil to pass through in the case of.
Here, for example, by setting a predetermined value to a value higher than the hydraulic pressure generated by the own weight of the movable table, the movable table does not lower only by its own weight, so that the lowering of the movable table is controlled by the pressure oil discharged from the pump. It becomes possible.

The press brake of the fourth invention is the press brake of the first invention, and the hydraulic cylinder has a cylinder tube and a piston portion inserted into the cylinder tube and slidable on the inner peripheral surface of the cylinder tube. .. The area of the first surface of the surface forming the second extension chamber of the piston portion that is perpendicular to the expansion and contraction direction is the area of the second surface of the surface that forms the contraction chamber of the piston portion that is perpendicular to the expansion and contraction direction. Is the same as.

By setting the area of the first surface and the area of the second surface to the same area in this way, it becomes easy to set the speed and the separation speed in the high-speed approach region to the same speed. That is, since the area of the first surface and the area of the second surface are the same, only by reversing the suction and discharge directions of the pump, the load on the motor that drives the pump is about the same, and the speed approaches at high speed. The speed in the area and the separation speed can be made similar. Therefore, the movable table can be easily controlled without going through the oil amount replenishment circuit for replenishing the oil amount.

It should be noted that the fact that the area of the first surface and the area of the second surface are the same includes a mechanical error.
The press brake of the fifth invention is the press brake of the fourth invention, and the hydraulic cylinder further has a rod-shaped member inserted into a hole formed in the piston portion along the expansion / contraction direction. The piston part is inserted into the cylinder tube so that the longitudinal direction is along the expansion and contraction direction, and the tip is connected to the movable table, and the piston is fixed to the piston rod and slidable on the inner peripheral surface of the cylinder tube. ,have. The hole is formed from the opening provided in the piston to the piston rod, and the end of the hole on the piston rod side is closed. The rod-shaped member has a sliding portion at its tip that is slidable with respect to the inner peripheral surface of the hole. The second extension chamber is formed by a space inside the hole portion and surrounded by the rod-shaped member and the piston portion. The first extension chamber is formed by a space surrounded by a piston portion, a rod-shaped member, and a cylinder tube. The contraction chamber is formed by a space surrounded by a piston portion and a cylinder tube. The first surface is a portion of the surface of the piston rod facing the second extension chamber that faces the sliding portion. The second surface is the surface portion of the piston facing the contraction chamber.

By setting the area of the first surface and the area of the second surface to the same area in this way, the movable table can be easily controlled without going through the oil amount replenishment circuit for replenishing the oil amount.
The press brake of the sixth invention is the press brake of the first or second invention, further including a cutoff unit, a cutoff unit, and a control unit for controlling the pump. The blocking unit can block the flow of oil between the first discharging unit and the first extension chamber. The control unit shuts off the shutoff unit, supplies the oil discharged from the first discharge portion of the pump to the second extension chamber, brings the movable table closer to the fixed table to the first predetermined position, and the movable table becomes the first. 1 When the predetermined position is reached, the shutoff portion enables the flow of oil, and the oil discharged from the first discharge portion of the pump is supplied to the first extension chamber and the second extension chamber to move to the second predetermined position. When the table is brought close to the fixed table and the movable table reaches the second predetermined position, the shutoff portion is shut off and the oil discharged from the second discharge portion of the pump is supplied to the shrink chamber to move the movable table from the fixed table. Separate.

In this way, the approach speed of the variable table to the fixed table can be changed from high speed to low speed simply by changing the state in which the supply of oil to one of the two extension chambers is stopped from the state in which the supply is started. Since the pressing force can be increased, stable operation is facilitated with simple control.
The press brake of the seventh invention is the press brake of the first invention, and the pump is a constant capacity type bidirectional pump.

As described above, the approach speed of the variable table to the fixed table can be increased from a high speed by simply changing the state in which oil is supplied to only one of the two extension chambers to the state in which oil is supplied to both extension chambers. It is possible to change to a lower speed and increase the pressing force. Therefore, the constant-capacity bidirectional pump can be used without using the variable-capacity bidirectional pump and the system in which the discharge amount is variable, and the control can be easily performed.

The press brake of the eighth invention is the press brake of the first invention, further comprising an electric servomotor for driving the pump.
Here, there is also hydraulic control using a servo valve, but the cost of the hydraulic equipment is high and the management of contamination in the hydraulic oil becomes a heavy burden. Moreover, since the motor is constantly driven, it cannot be said to be energy saving.

On the other hand, in the present invention, since the pump is directly driven by the electric servomotor, the control of contamination in the hydraulic oil can be performed as usual, the hydraulic opening configuration and control are simplified, and the cost of the hydraulic equipment is reduced. .. In addition, since the electric servomotor is operated when necessary, energy saving can be achieved.
The bending method of the ninth invention is a bending method for bending a plate-shaped member, and includes a first approach step, a second approach step, and a separation step. In the first approach step, oil is discharged from the first discharge portion of the pump to supply the oil to the second extension chamber of the hydraulic cylinder, and the oil is sucked from the contraction chamber of the hydraulic cylinder to the second discharge portion of the pump. , Bring the movable table on which the punch is mounted close to the fixed table on which the die is mounted. In the second approach step, oil is discharged from the first discharge portion of the pump to supply the oil to the first extension chamber and the second extension chamber, and the oil is sucked from the contraction chamber to the second discharge portion of the pump. Bring the movable table closer to the fixed table. In the separation step, the movable table is fixed by discharging oil from the second discharge portion of the pump to supply the oil to the contraction chamber and sucking the oil from the first extension chamber of the hydraulic cylinder to the first discharge portion of the pump. Keep away from the table.

As described above, a hydraulic cylinder and a bidirectional pump having two first extension chambers and a second extension chamber are provided. When the movable table is brought close to the fixed table in an area other than the processing setting area set for bending the work, the oil from the pump is not supplied to the first extension chamber but to the second extension chamber. By supplying only the oil pressure, the area affected by the hydraulic pressure when the hydraulic cylinder is extended can be reduced. Therefore, the movable table can be brought close to the fixed table at high speed in an area other than the machining setting area. A region other than the machining setting region in such an approach can be said to be a high-speed approach region.

Further, by supplying oil to the first extension chamber, oil is supplied to both the first extension chamber and the second extension chamber in the machining setting area, and the hydraulic pressure acts when the hydraulic cylinder is extended. The area to be used can be increased. Therefore, the movable table can be brought closer to the fixed table by increasing the pressing force at a low speed in the machining setting area. The machining setting region in such an approach can be said to be a low-speed approach region.

That is, the approach speed of the variable table to the fixed table is changed from high speed to low speed only by changing the state in which oil is supplied to only one of the two extension chambers to the state in which oil is supplied to both extension chambers. Since the pressurizing pressure can be increased, the equivalent efficient ram operation is possible without using a complicated bidirectional pump and system to make the discharge rate variable.
Further, the machining setting region (low-speed approach region) may be an region where the die and the punch actually come into contact with the work and the plate-shaped member is bent, or the die and the punch actually come into contact with the work. It may be set to a region including a region where the plate-shaped member is bent.

According to the present invention, it is possible to provide a press brake and a bending method capable of stable operation by simple control.

(A) A front schematic view of the press brake according to the embodiment of the present invention, (b) a side schematic view of FIG. 1 (a). (A) A cross-sectional view showing a state in which the hydraulic cylinder is contracted in the press brake of FIG. 1, (b) a cross-sectional view showing a state in which the hydraulic cylinder of FIG. 2 (a) is extended, and (c) AA of FIG. 2 (a). Cross-sectional view of the arrow between ´. The figure which shows the structure of the cylinder drive part of the press brake of FIG. The figure which shows the control structure of the press brake of FIG. The flow chart which shows the operation of the press brake of FIG. The figure which shows the time change of the position of the ram in the operation of FIG. (A) A diagram showing a state in which the hydraulic cylinder is contracted in a modified example of the embodiment according to the present invention, and (b) a sectional view showing a state in which the hydraulic cylinder of FIG. 7 (a) is extended.

The press brake of the embodiment according to the present invention will be described below with reference to the drawings.
<1. Configuration>
(1-1. Outline of Press Brake 1)
FIG. 1A is a front schematic view showing the configuration of the press brake 1 of the present embodiment. FIG. 1B is a schematic side view of the press brake 1. As shown in FIGS. 1A and 1B, the press brake 1 of the present embodiment includes a frame 10, a table 11, a ram 12, a pair of hydraulic cylinders 13a and 13b, and a cylinder drive unit. It includes 14a and 14b, a control unit 15, and an operation unit 16.

The frame 10 has a pair of plate portions 10a and 10b arranged at predetermined intervals in the left-right direction. As shown in FIG. 1B, the plate portions 10a and 10b are members having a substantially C shape in a side view.
The table 11 is fixed to the lower part of the plate portions 10a and 10b, and the die 17 can be mounted on the upper surface thereof.

The ram 12 is supported on the upper part of the plate portions 10a and 10b so as to be able to move up and down, and the punch 18 can be attached to the lower surface. The ram 12 descends and approaches the table 11 arranged under the ram 12, and the plate-shaped work W is bent by the cooperation of the die 17 and the punch 18.
The pair of hydraulic cylinders 13a and 13b are arranged along the vertical direction above the left and right ends of the ram 12 in order to move the ram 12 up and down. The hydraulic cylinder 13a is fixed to the plate portion 10a of the frame 10, and the hydraulic cylinder 13b is fixed to the plate portion 10b of the frame 10. The hydraulic cylinders 13a and 13b are arranged so that their expansion and contraction directions coincide with each other in the vertical direction.

The cylinder drive unit 14a drives the hydraulic cylinder 13a by supplying or sucking pressure oil. The cylinder drive unit 14b drives the hydraulic cylinder 13b using the pressure oil by supplying or sucking the pressure oil.
The control unit 15 controls the cylinder drive units 14a and 14b. The operation unit 16 is input by an operator and has a foot switch 95, an operation panel 94, and the like, as shown in FIG. 2 to be described later.

(1-2. Hydraulic cylinders 13a, 13b)
Next, the configurations of the hydraulic cylinders 13a and 13b will be described. Since the hydraulic cylinders 13a and 13b have the same configuration, the hydraulic cylinders 13a provided on the left side in FIG. 1 (a) are used to configure the configurations. explain.
FIG. 2A is a cross-sectional view showing a state in which the hydraulic cylinder 13a is contracted. FIG. 2B is a cross-sectional view showing a state in which the hydraulic cylinder 13a is extended. As shown in FIGS. 2 (a) and 2 (b), the hydraulic cylinder 13a includes a cylinder tube 20, a piston portion 21, a rod-shaped member 22, a first extension chamber 23, a second extension chamber 24, and the like. It has a contraction chamber 25 and.

The cylinder tube 20 has a cylindrical shape and is fixed to the frame 10 shown in FIG. 1 (a). The piston portion 21 is slidable on the inner peripheral surface of the cylinder tube 20, and has a piston 31 and a piston rod 32.
The piston 31 has a cylindrical shape, is in contact with the inner peripheral surface of the cylinder tube 20, and slides on the inner peripheral surface of the cylinder tube 20 along the expansion / contraction direction X (vertical direction). The piston rod 32 has a cylindrical shape and is inserted into the cylinder tube 20 along the vertical direction, and the upper end thereof is fixed to the piston 31. Further, the lower end of the piston rod 32 is fixed to the ram 12 below the cylinder tube 20.

A cylindrical hole 33 is formed from the opening 31a formed on the upper surface of the piston 31 to the piston rod 32 downward. The hole 33 does not penetrate the piston rod 32, and the lower end of the hole 33 is closed.
The rod-shaped member 22 is slidable relative to the inner peripheral surface of the hole 33, and has a sliding portion 34 and a rod portion 35.

The sliding portion 34 has a cylindrical shape and slides on the inner peripheral surface of the hole portion 33 along the vertical direction. The rod portion 35 has a cylindrical shape and is inserted into the cylinder tube 20 along the vertical direction, and the lower end thereof is fixed to the sliding portion 34. Further, the rod portion 35 is arranged so that the upper end protrudes from the cylinder tube 20 and is fixed to the frame 10. That is, the rod-shaped member 22 is fixed to the frame 10 together with the cylinder tube 20 and does not move. Further, the rod-shaped member 22 is formed with a cylinder flow passage 36 through which oil flows along the vertical direction. The cylinder flow passage 36 has an opening 36a on the lower surface of the sliding portion 34.

The first extension chamber 23 is a hollow columnar space surrounded by the cylinder tube 20, the piston portion 21, and the rod-shaped member 22. The first extension chamber 23 is formed above the piston portion 21, and can be said to be a space formed around the rod-shaped member 22.
When pressure oil is supplied to the first extension chamber 23, pressure is applied to the annular upper surface 31b of the piston 31, and the piston portion 21 moves downward.

The second extension chamber 24 is a columnar space in the hole 33, and is a space surrounded by the piston portion 21 and the rod-shaped member 22. When pressure oil is supplied to the second extension chamber 24 from the cylinder flow passage 36, pressure is applied to the bottom surface 33a of the hole portion 33, and the piston portion 21 moves downward. The bottom surface 33a of the hole 33 can be said to be the surface of the piston portion 21 facing the sliding portion 34.
Here, the area of the bottom surface 33a is formed smaller than the area of the top surface 31b. Since the first extension chamber 23 and the second extension chamber 24 are columnar spaces, the cross-sectional area perpendicular to the expansion / contraction direction of the second extension chamber 24 is the cross-sectional area perpendicular to the expansion / contraction direction of the first extension chamber 23. It can be said that it is smaller than.

The contraction chamber 25 is a hollow columnar space below the piston 31 and between the piston rod 32 and the cylinder tube 20. When pressure oil is supplied to the contraction chamber 25, pressure is applied to the annular lower surface 31c of the piston 31 facing the contraction chamber 25, and the piston portion 21 moves upward. Since the contraction chamber 25 is annular, the bottom surface 20a of the cylinder tube 20 is also annular and has the same area as the bottom surface 31c.

FIG. 2C is a cross-sectional view taken along the line between AA'in FIG. 2A.
The hatched area from diagonally upper right to diagonally lower left in FIG. 2C shows the bottom surface 33a, and the hatched area from diagonally lower right to diagonally upper left represents the bottom surface 20a of the cylinder tube 20. Shown. The bottom surface 33a and the bottom surface 20a shown in FIG. 2C are formed in the same area. Since the bottom surface 20a and the bottom surface 31c have the same shape as described above, the bottom surface 33a and the bottom surface 31c are set to have the same area.

That is, the bottom surface 33a of the hole 33 facing the second extension chamber 24, which is a surface perpendicular to the extension direction (which can be said to be the vertical direction), and the contraction chamber 25, which is a surface perpendicular to the extension direction. The lower surface 31c of the facing piston 31 is set to have the same area.
(1-3. Cylinder drive units 14a, 14b)
Next, the cylinder drive units 14a and 14b that drive the hydraulic cylinders 13a and 13b will be described. Since the cylinder drive unit 14a and the cylinder drive unit 14b have the same configuration, the configuration will be described using the cylinder drive unit 14a.

FIG. 3 is a hydraulic circuit diagram showing the configuration of the cylinder drive unit 14a. As shown in FIG. 3, the cylinder drive unit 14a includes a hydraulic circuit 40, a constant-capacity bidirectional pump 41, a servomotor 42, and a tank 43.
The constant capacity type bidirectional pump 41 has a first discharge unit 41a and a second discharge unit 41b. The constant-capacity bidirectional pump 41 discharges oil from one of the first discharge unit 41a and the second discharge unit 41b and sucks oil from the other.

The servomotor 42 controls the rotation of the constant-capacity bidirectional pump 41. As will be described later, the servomotor 42 is controlled based on the detection result of the linear sensor 93 that detects the position of the ram 12. Increasing the rotation speed of the servomotor 42 increases the discharge amount of the constant-capacity bidirectional pump 41. When the rotation speed of the servomotor 42 is lowered, the discharge amount of the constant capacity type bidirectional pump 41 is reduced. When the rotation direction of the servomotor 42 is reversed in the forward and reverse directions, the oil discharge direction of the constant capacity type bidirectional pump 41 is reversed. The motion of the ram 12 can be changed by servo-controlling the servo motor 42. By directly driving the constant-capacity bidirectional pump 41 with the servomotor 42 in this way, control with good responsiveness becomes possible.

There is also hydraulic control using a servo valve, but the cost of hydraulic equipment is high and the management of contamination in hydraulic oil becomes a heavy burden. Moreover, since the motor is constantly driven, it cannot be said to be energy saving. However, in the present embodiment, since the constant capacity bidirectional pump 41 is directly driven by the servomotor 42, the control of contamination in the hydraulic oil can be performed as usual, the hydraulic pressure opening configuration and control are simplified, and the hydraulic pressure is increased. The cost of the equipment is also reduced. Further, since the servomotor 42 is moved when necessary, energy saving can be achieved.

Oil is stored in the tank 43.
The hydraulic circuit 40 connects the hydraulic cylinder 13a, the constant-capacity bidirectional pump 41, and the tank 43.
(1-3-1. Hydraulic circuit 40)
As shown in FIG. 3, the hydraulic circuit 40 mainly includes a first main circuit 51, a second main circuit 52, an oil amount replenishment circuit 53, and a first extension chamber oil amount adjusting circuit 54.

(First main circuit 51)
The first main circuit 51 connects the first discharge portion 41a of the constant-capacity bidirectional pump 41 with the first extension chamber 23 and the second extension chamber 24. The first main circuit 51 mainly has a first flow passage 61, a second flow passage 62, a third flow passage 63, and an on-off valve 64.
The first flow passage 61 is connected to the first discharge portion 41a of the constant capacity type bidirectional pump 41. The second flow passage 62 connects between the first flow passage 61 and the first extension chamber 23. The third flow passage 63 connects between the first flow passage 61 and the cylinder flow passage 36. The on-off valve 64 is provided in the second flow passage 62, and can open and close the second flow passage 62. A solenoid valve is used as the on-off valve 64. The on-off valve 64 can block or open the flow of oil between the first discharge portion 41a and the first extension chamber 23.

(Second main circuit 52)
The second main circuit 52 connects between the second discharge portion 41b of the constant-capacity bidirectional pump 41 and the contraction chamber 25. The second main circuit 52 has a fourth flow passage 71, a check valve 72, a fifth flow passage 73, a relief valve 74, and a stop valve 75. The fourth flow passage 71 connects between the second discharge portion 41b of the constant-capacity bidirectional pump 41 and the contraction chamber 25. The check valve 72 is provided in the fourth flow passage 71, and allows oil to flow in the direction from the discharge portion 41b to the contraction chamber 25, and blocks the flow of oil in the direction from the contraction chamber 25 to the discharge portion 41b. .. The fifth flow passage 73 branches from the fourth flow passage 71 so as to bypass the check valve 72, joins the fourth flow passage 71, and is arranged in parallel with the check valve 72. When the oil flows from the contraction chamber 25 toward the discharge portion 41b, the oil passes through the fifth flow passage 73.

The relief valve 74 is a so-called counterbalance valve, and is provided in the fifth flow passage 73. The oil discharged from the contraction chamber 25 flows into the fifth flow passage 73 because the check valve 72 is provided in the fourth flow passage 71, and when the oil pressure exceeds the set value, the relief valve 74 is pushed open and discharged. It flows toward the portion 41b. By appropriately setting the set value of the relief valve 74, it is possible to suppress the lowering of the hydraulic cylinder 13a due to the weight of the ram 12, and it is possible to perform hydraulic control by positive torque.

Two stop valves 75 are provided in the fourth flow passage 71 between the check valve 72 and the relief valve 74 and the discharge portion 41b. These stop valves 75 are provided to ensure the safety of the operator, and when they are closed, the device does not operate even if the constant capacity type bidirectional pump 41 is driven.
(Oil amount replenishment circuit 53)
The oil amount replenishment circuit 53 connects between the fourth flow passage 71 of the second main circuit 52 and the tank 43. The oil amount replenishment circuit 53 is provided with a switching valve, a plurality of relief valves, a plurality of check valves, and the like. When the amount of oil to be circulated is insufficient, the oil stored in the tank 43 is replenished to the second main circuit 52 from the oil amount replenishment circuit 53 via the merging portion 91a with the fourth flow passage 71. Further, the oil stored in the tank 43 is replenished to the first main circuit 51 via the merging portion 91b.

(1st extension chamber oil amount adjusting circuit 54)
The first extension chamber oil amount adjusting circuit 54 connects between the first extension chamber 23 and the tank 43, supplies oil to the first extension chamber 23, or discharges oil from the first extension chamber 23.
As will be described in detail later, in the present embodiment, when the ram 12 is lowered at high speed, the oil from the constant capacity type bidirectional pump 41 is not supplied to the first extension chamber 23, but is supplied to the second extension chamber 24. Only supply. In this way, when the oil from the constant capacity type bidirectional pump 41 is supplied only to the second extension chamber 24 to extend the hydraulic cylinder 13a, the first extension chamber 23 is prevented from being evacuated. Oil is supplied from the oil amount adjusting circuit 54 to the first extension chamber 23. Further, when the ram 12 is raised at a high speed, excess oil is discharged from the first extension chamber 23.

The first extension chamber oil amount adjusting circuit 54 mainly includes a prefill valve 81, a control valve 82, a sixth flow passage 83, and a seventh flow passage 84. The sixth flow passage 83 connects the portion of the second flow passage 62 between the first extension chamber 23 and the on-off valve 64 and the tank 43. The prefill valve 81 is provided in the sixth flow passage 83.
The seventh flow passage 84 connects a portion of the fourth flow passage 71 between the stop valve 75 and the discharge portion 41b and the prefill valve 81. The control valve 82 is a solenoid valve provided in the seventh flow passage 84, and opens and closes the flow of oil from the fourth flow passage 71 to the prefill valve 81.

When the pressure oil is not supplied from the 7th flow passage 84, the prefill valve 81 makes it possible to supply the oil of the tank 43 to the 1st extension chamber 23 through the 6th flow passage 83, and the oil flows in the opposite direction. To shut off. As will be described in detail later, when the ram 12 is lowered at high speed, the pressure oil is not supplied from the seventh flow passage 84, and the oil is supplied from the tank 43 to the first extension chamber 23 as the piston portion 21 is lowered. Will be replenished. On the other hand, when the ram 12 is raised at high speed, the control valve 82 is opened and pressure oil is supplied to the prefill valve 81 from the seventh flow passage 84. By supplying this pressure oil, the prefill valve 81 is opened so that the oil can flow in the opposite direction, and the oil in the first extension chamber 23 can flow to the tank 43 through the sixth flow passage 83. Become. As a result, the oil is discharged from the first extension chamber 23 to the tank 43 as the piston portion 21 rises.

(Other configurations)
As another configuration, for example, a pressure sensor 92 for measuring the pressure of the second flow passage 62 is provided. The detected value of the pressure sensor 92 is fed back to the control unit 15, and when the value of the pressure sensor 92 becomes too high, the control unit 15 stops the device.
An eighth flow path 85 connecting the on-off valve 64 and the tank 43 is provided, and the eighth flow path 85 is provided with a throttle or the like. The eighth flow path 85 communicates with the second flow path 62 when the first flow path 61 and the second flow path 62 are blocked by the on-off valve 64.

(1-4. Control configuration)
FIG. 4 is a diagram showing a control configuration of the press brake 1 of the present embodiment. As shown in FIG. 4, a linear sensor 93 for detecting the position of the ram 12 is provided, and a position signal detected by the linear sensor 93 as an example of the position detection unit is input to the control unit 15. The servomotor 42 is connected to the control unit 15 via the servo amplifier 96.

An operation unit 16 is connected to the control unit 15. The operator inputs the operation via the operation unit 16. The operation unit 16 is provided with an operation panel 94, a foot switch 95, and the like. The operation panel 94 is provided with a monitor, a press condition setting switch, and the like. The foot switch 95 is a foot switch that drives the hydraulic cylinders 13a and 13b to raise and lower the ram 12.

The control unit 15 controls the servomotor 42 by transmitting a signal to the servo amplifier 96 based on the position signal detected by the linear sensor 93 so as to follow the setting input by the operation unit 16. The control unit 15 also controls the hydraulic circuit 40. For example, the control unit 15 controls the opening and closing of the on-off valve 64 to supply or stop the supply of oil to the first extension chamber 23. Further, the control unit 15 controls the opening and closing of the control valve 82 to open the prefill valve 81, enabling the flow of oil in the opposite direction (flow from the first extension chamber 23 to the tank 43).

<2. Operation>
Next, the operation of the press brake 1 of the present embodiment will be described. FIG. 5 is a flow chart showing the operation of the press brake 1 of the first embodiment. FIG. 6 is a diagram showing a time change of the position of the ram 12 during operation.
The operation will be described as starting from a state in which the ram 12 is arranged at the upper limit position (see h1 in FIG. 6).

First, in step S10, when the control unit 15 detects that the operator has stepped on the foot switch 95, it controls the servomotor 42 in step S11 to drive the constant-capacity bidirectional pump 41.
In step S11, the constant-capacity bidirectional pump 41 discharges oil from the discharge unit 41a and sucks oil from the discharge unit 41b with the on-off valve 64 closed. As a result, the pressure oil discharged from the constant-capacity bidirectional pump 41 flows into the second extension chamber 24 through the first flow passage 61, the third flow passage 63, and the cylinder flow passage 36 in this order. On the other hand, since the second flow passage 62 is blocked, the pressure oil from the constant capacity type bidirectional pump 41 is not supplied to the first extension chamber 23. In this way, the ram 12 can be lowered at high speed by supplying the pressure oil from the constant-capacity bidirectional pump 41 only to the second extension chamber 24 having a small cross-sectional area (see t1 to t2 in FIG. 6). ).

Further, oil is sucked from the contraction chamber 25 to the discharge portion 41b of the constant capacity type bidirectional pump 41.
In this way, the pressure oil is supplied from the constant capacity type bidirectional pump 41 to the second extension chamber 24, and the oil is sucked from the contraction chamber 25 into the constant capacity type bidirectional pump 41, so that the hydraulic cylinders 13a and 13b The piston portion 21 of the above is lowered, and the ram 12 is lowered.
When the piston portion 21 starts to descend from the upper limit position h1, the oil passes through the fifth flow passage 73 so as to bypass the check valve 72 portion of the fourth flow passage 71, but the relief valve 74 The distribution is stopped until the oil pressure exceeds the specified level. In this way, since the oil is suppressed from flowing out from the contraction chamber 25 by the weight of the ram 12, the ram 12 can be lowered by hydraulic pressure with a positive torque, so that the ram 12 is stable at a speed faster than the free fall. Downward control is possible.

Further, as the piston portion 21 descends, oil flows into the first extension chamber 23 from the tank 43 via the prefill valve 81.
Next, in step S12, when the control unit 15 detects that the position of the ram 12 has reached the switching position (see h2 in FIG. 6) using the detection value of the linear sensor 93, in step S13, the on-off valve 64 To switch to the open state. As a result, the pressure oil discharged from the constant-capacity bidirectional pump 41 flows into the first extension chamber 23 through the second flow passage 62. The supply of pressure oil to the second extension chamber 24 is continuing. The area between the upper limit position h1 and the switching position h2 is an example of a high-speed approach region, and is a portion shown as G1 (fast descent) in the graph shown in FIG.

By supplying the pressure oil to the first extension chamber 23 and the second extension chamber 24 in this way, the supply portion of the pressure oil is increased, the descending speed is slowed, and the pressing force is increased. Then, while the ram reaches the lower limit position, the work W is bent (t2 to t3 in FIG. 6).
Next, in step S14, when the control unit 15 detects that the position of the ram 12 has reached the lower limit position (see h3 in FIG. 6) using the detection value of the linear sensor 93, in step S15, the on-off valve 64 To the shutoff state. As a result, the oil flow is blocked between the second flow passage 62 and the first flow passage 61. In FIG. 3, when the on-off valve 64 is shut off, the second flow passage 62 communicates with the tank 43 via the eighth flow passage 85. This has the function of lowering the pressure in the first extension chamber 23. The amount of oil flowing is limited by the throttle installed in the eighth flow path 85 connecting the on-off valve 64 and the tank 43. Further, the switching position h2 to the lower limit position h3 are regions set for machining, which is an example of a low-speed approach region, and the graph is a portion shown as G2 (slow descent, pressurization).

Next, in step S16, the control unit 15 switches the control valve 82 to enable the supply of pressure oil from the fourth flow passage 71 to the prefill valve 81.
Next, in step S17, the control unit 15 controls the servomotor 42 to discharge the oil from the second discharge unit 41b, and sucks the oil from the first discharge unit 41a. Drive in reverse.

By driving the constant-capacity bidirectional pump 41, the oil from the constant-capacity bidirectional pump 41 is supplied to the contraction chamber 25, and the oil in the second extension chamber 24 is sucked into the constant-capacity bidirectional pump 41. Then, the piston portion 21 rises. At the time of ascending, the mass of the ram 12 acts as a counter force.
Here, since the flow of the second flow passage 62 is blocked, the oil in the first extension chamber 23 is not sucked by the drive of the constant capacity type bidirectional pump 41. On the other hand, since oil is supplied to the contraction chamber 25 via the fourth flow passage 71, pressure oil is supplied to the prefill valve 81 via the control valve 82 and the seventh flow passage 84. By supplying this pressure oil, the prefill valve 81 is opened from the first extension chamber 23 toward the tank 43. As a result, the oil is returned from the first extension chamber 23 to the tank 43 as the piston portion 21 rises. The area of the lower surface 31c of the piston portion 21 facing the contraction chamber 25 is the same size as the bottom surface 33a facing the second extension chamber 24 and is formed to be small. Therefore, for example, during rapid descent (t1 to 1). By setting the discharge amount of the constant capacity type bidirectional pump 41 to be the same as that of t2), the ram 12 can be raised at high speed (see t4 to t5 in FIG. 6). In the graph shown in FIG. 6, it is a part shown as G3 (rapid rise).

Then, in step S18, when the control unit 15 detects that the position of the ram 12 has reached the upper limit position (see h1 in FIG. 6) using the detection value of the linear sensor 93, the control unit 15 drives the pump in step S19. Stop (see t5 in FIG. 6). Subsequently, in step S20, the control unit 15 returns the switched control valve 82 to close the opening of the prefill valve 81 from the first extension chamber 23 to the tank 43. These steps S19 and S20 may be performed substantially at the same time.

The second extension chamber 24 and the first discharge portion 41a communicate with each other during the approach between the upper limit position h1 and the switching position h2 and between the lower limit position h3 and the upper limit position h1, and the contraction chamber 25. And the second discharge portion 41b communicate with each other, forming a substantially closed circuit. Since the area of the bottom surface 33a acting on the drive of the piston portion 21 in the second extension chamber 24 and the area of the bottom surface 31c acting on the drive of the piston portion 21 in the contraction chamber 25 are the same, the rotation of the constant capacity type bidirectional pump 41 By simply reversing the directions, the speed between the approach to the upper limit position h1 to the switching position h2 and the speed between the separation from the lower limit position h3 to the upper limit position h1 can be made substantially the same.

<3. Features>
(3-1)
As shown in FIGS. 1 and 2 (a) to 2 (c), the press brake 1 of the present embodiment is a press that bends a work W (an example of a plate-shaped member) by a punch 18 and a die 17. The brake includes a ram 12 (an example of a movable table), a table 11 (an example of a fixed table), hydraulic cylinders 13a and 13b, and a constant-capacity bidirectional pump 41 (an example of a pump). A punch 18 is attached to the ram 12. A die 17 is mounted on the table 11. The hydraulic cylinders 13a and 13b have a first extension chamber 23 and a second extension chamber 24 to which oil is supplied when expanding, and a contraction chamber 25 to which oil is supplied when contracting. The hydraulic cylinders 13a and 13b expand and contract to bring the ram 12 closer to or further from the table 11. The constant-capacity bidirectional pump 41 has a first discharge unit 41a connected to the first extension chamber 23 and the second extension chamber 24, and a second discharge unit 41b connected to the contraction chamber 25. When the oil is discharged from one of the first discharge unit 41a and the second discharge unit 41b, the oil is sucked from the other.

Here, the motion of the ram 12 is basically a fast descent, a slow descent, a lower limit stop, and a fast rise. When all of this motion is performed by the servomotor, the rotation speed of the servomotor must be changed significantly in one cycle. Although it is possible to change the servomotor in this way, the efficiency is reduced.
Therefore, in the press brake 1 of the present embodiment, the hydraulic cylinders 13a and 13b are used to secure the basic form of the motion of the ram 12, and the efficiency is improved by suppressing the change in the rotation speed of the servomotor during one cycle. .. On the other hand, the characteristics of servo control are utilized to enable fine correction of motion and improve moldability.

As described above, the hydraulic cylinders 13a and 13b having the two first extension chambers 23 and the second extension chamber 24 and the constant capacity type bidirectional pump 41 are provided. When the ram 12 is brought closer to the table 11 at the upper limit position h1 to the switching position h2 (an example of an area other than the processing setting area set for bending the workpiece), the constant capacity type bidirectional pump 41 By supplying the oil from the above to only the second extension chamber 24 without supplying it to the first extension chamber 23, the area affected by the hydraulic pressure when the hydraulic cylinders 13a and 13b are extended can be reduced. Therefore, the ram 12 can be brought closer to the table 11 at high speed at the upper limit position h1 to the switching position h2. A region other than the machining setting region in such an approach can be said to be a high-speed approach region.

Further, by supplying oil to the first extension chamber 23, oil is supplied to both the first extension chamber 23 and the second extension chamber 24 in the processing setting area, and the hydraulic cylinders 13a and 13b are extended. The area actuated by the hydraulic pressure can be increased. Therefore, the ram 12 can be brought closer to the table 11 by increasing the pressing force at a low speed in the machining setting region. The processing region in such an approach can be said to be a low-speed approach region.

That is, the ram 12 approaches the table 11 only by changing the state in which oil is supplied only to one of the two extension chambers 23 and 24 to the state in which oil is supplied to both extension chambers 23 and 24. Since the speed can be changed from high speed to low speed and the pressing force can be increased, it is possible to perform the same efficient ram operation without using a complicated variable capacitance type bidirectional pump and system to make the discharge amount variable. It becomes.

Further, the machining setting region (low-speed approach region) may be an region in which the die 17 and the punch 18 actually come into contact with the work W and the plate-shaped member is bent, or the die 17 and the punch 18 are actually punched. 18 may be a region including a region where the plate-shaped member is bent in contact with the work W. That is, the switching position h2 may be a position where the punch 18 contacts the work W, or may be set at a position higher than the position where the punch 18 contacts the work W.

(3-2)
As shown in FIG. 3, the press brake 1 of the present embodiment is an example of a relief valve 74 (an example of a resistance generating portion) that generates a resistance against the discharge of oil from the hydraulic cylinders 13a and 13b due to the lowering of the ram 12. ) Is further provided.
As a result, when the ram 12 is lowered, a counter force can be generated against the lowering due to its own weight. Therefore, it is possible to control the descent of the ram 12 by the oil discharged from the constant capacity type bidirectional pump 41. If a counter force is not generated against the descent due to its own weight, it will be controlled by a negative torque when the ram 12 descends, and it tends to become unstable due to the difference in viscosity due to the temperature change of the hydraulic oil, and the speed is increased or accelerated. It was difficult to speed up. However, by generating a counter force, the lowering of the ram 12 can be controlled by a positive torque due to hydraulic pressure. That is, the rotation speed and torque of the servomotor 42 that operates the constant-capacity bidirectional pump 41 directly affect the ram operation, and stable and fast movable table operation becomes possible.

(3-3)
In the press brake 1 of the present embodiment, the relief valve 74 is connected to the contraction chamber 25, shuts off the oil when the hydraulic pressure is smaller than the predetermined value, and allows the oil to pass when the hydraulic pressure is equal to or higher than the predetermined value.
Here, for example, by setting a predetermined value to a value higher than the hydraulic pressure generated by the own weight of the ram 12, the ram 12 does not descend only by its own weight, so that the ram 12 can be moved by the pressure oil discharged from the constant capacity type bidirectional pump 41. It is possible to control the descent of the table.

(3-4)
In the press brake 1 of the present embodiment, the hydraulic cylinders 13a and 13b have a cylinder tube 20 and a piston portion 21 inserted into the cylinder tube 20 and slidable on the inner peripheral surface of the cylinder tube 20. The area of the bottom surface 33a (an example of the first surface) perpendicular to the expansion / contraction direction of the surface forming the second extension chamber 24 of the piston portion 21 is the expansion / contraction direction of the surface forming the contraction chamber 25 of the piston portion 21. It is the same as the area of the lower surface 31c (an example of the second surface) perpendicular to the vertical surface.

By making the area of the bottom surface 33a and the area of the bottom surface 31c the same in this way, it becomes easy to set the speed in the high-speed approach region and the separation speed for separating the ram 12 from the table 11 to the same speed. That is, since the area of the bottom surface 33a and the area of the bottom surface 31c are the same, the servomotor 42 that drives the constant-capacity bidirectional pump 41 simply by reversing the suction and discharge directions of the constant-capacity bidirectional pump 41. With the same load, the speed (time t1 to t2) and the separation speed (speed from time t4 to t5) in the high-speed approach region can be set to the same speed. Therefore, the ram 12 can be easily controlled without going through the oil amount replenishment circuit 53 for replenishing the oil amount.

The fact that the area of the bottom surface 33a and the area of the bottom surface 31c are the same includes a mechanical error.
(3-5)
In the press brake 1 of the present embodiment, as shown in FIG. 2, the hydraulic cylinders 13a and 13b further have a rod-shaped member 22 inserted into a hole 33 formed in the piston portion 21 along the expansion / contraction direction. .. The piston portion 21 is inserted into the cylinder tube 20 so that the longitudinal direction follows the expansion / contraction direction, and the piston rod 32 whose tip is connected to the ram 12 and the piston rod 32 are fixed to the piston rod 32 and slide on the inner peripheral surface of the cylinder tube 20. It has a movable piston 31 and. The hole 33 is formed from the opening 31a provided in the piston 31 to the piston rod 32, and the end of the hole 33 on the piston rod 32 side is closed. The rod-shaped member 22 has a sliding portion 34 at its tip, which is slidable with respect to the inner peripheral surface of the hole portion 33. The second extension chamber 24 is formed by a space inside the hole 33 and surrounded by the rod-shaped member 22 and the piston 21. The first extension chamber 23 is formed by a space surrounded by a piston portion 21, a rod-shaped member 22, and a cylinder tube 20. The contraction chamber 25 is formed by a space surrounded by the piston portion 21 and the cylinder tube 20. The bottom surface 33a (an example of the first surface) is a portion of the surface of the piston rod 32 facing the second extension chamber 24 that faces the sliding portion 34. The lower surface 31c (an example of the second surface) is a surface portion of the piston 31 facing the contraction chamber 25.

By making the area of the lower surface 31c and the area of the bottom surface 33a the same in this way, the ram 12 can be easily controlled without going through the oil amount replenishment circuit 53 for replenishing the oil amount.
(3-6)
As shown in FIG. 3, the press brake 1 of the present embodiment further includes an on-off valve 64 (an example of a shut-off unit), an on-off valve 64, and a control unit 15 for controlling a constant-capacity bidirectional pump 41. .. The on-off valve 64 can block the flow of oil between the first discharge portion 41a and the first extension chamber 23. The control unit 15 shuts off the on-off valve 64, supplies the oil discharged from the first discharge unit 41a of the constant-capacity bidirectional pump 41 to the first extension chamber 23, and switches the ram 12 to the switching position h2 (first). 1) The table 11 is approached to a predetermined position), and when the ram 12 reaches the switching position h2, the on-off valve 64 enables oil to flow and is discharged from the first discharge portion 41a of the constant-capacity bidirectional pump 41. The oil is supplied to the first extension chamber 23 and the second extension chamber 24 to bring the ram 12 closer to the table 11 to the lower limit position (an example of the second predetermined position), and when the ram 12 reaches the lower limit position, it opens and closes. The valve 64 is shut off, and the oil discharged from the second discharge portion 41b of the constant capacity type bidirectional pump 41 is supplied to the contraction chamber 25 to separate the ram 12 from the table 11.

In this way, the approach speed of the ram 12 to the table 11 is increased by simply switching from the state in which the supply of oil to the extension chamber 23 of the two extension chambers 23 and 24 is stopped to the state in which the supply is started. Since it is possible to increase the pressing force by changing from to low speed, stable operation becomes easy with simple control.
(3-7)
The press brake 1 of the present embodiment further includes a servomotor 42 (an example of an electric servomotor) that drives a constant-capacity bidirectional pump 41.

Here, there is also hydraulic control using a servo valve, but the cost of the hydraulic equipment is high and the management of contamination in the hydraulic oil becomes a heavy burden. Moreover, since the motor is constantly driven, it cannot be said to be energy saving.
On the other hand, in the present embodiment, since the constant capacity type bidirectional pump 41 is directly driven by the servomotor 42, the control of contamination in the hydraulic oil can be performed as usual, and the hydraulic pressure opening configuration and control are simplified. , The cost of hydraulic equipment is also reduced. Further, since the servomotor 42 is moved when necessary, energy saving can be achieved.

(3-8)
As shown in FIG. 5, the bending method of the present embodiment is a bending method for bending a work W (an example of a plate-shaped member), and steps S11 and S12 (an example of a first approach step). And steps S13 and S14 (an example of a second approaching step) and steps S17 and S18 (an example of a separation step). In steps S11 and S12 (an example of the first approach step), oil is discharged from the first discharge portion 41a of the constant capacity type bidirectional pump 41 (an example of the pump) into the second extension chamber 24 of the hydraulic cylinders 13a and 13b. Ram 12 to which the punch 18 is mounted by supplying oil and sucking oil from the contraction chambers 25 of the hydraulic cylinders 13a and 13b to the second discharge portion 41b of the constant-capacity bidirectional pump 41 (an example of a movable table). Is brought close to the table 11 (an example of a fixed table) on which the die 17 is mounted. In steps S13 and S14 (an example of the second approach step), oil is discharged from the first discharge portion 41a of the constant-capacity bidirectional pump 41 to supply the oil to the first extension chamber 23 and the second extension chamber 24. The ram 12 is brought closer to the fixed table by sucking oil from the contraction chamber 25 into the second discharge portion 41b of the constant capacity type bidirectional pump 41. In steps S17 and S18 (an example of the separation step), oil is discharged from the second discharge portion 41b of the constant-capacity bidirectional pump 41 to supply the oil to the contraction chamber 25, and the first extension chambers of the hydraulic cylinders 13a and 13b are supplied. The ram 12 is separated from the table 11 by sucking oil from the 23 to the first discharge portion 41a of the constant capacity type bidirectional pump 41.

As described above, the hydraulic cylinders 13a and 13b having the two first extension chambers 23 and the second extension chamber 24 and the constant capacity type bidirectional pump 41 are provided. When the ram 12 is brought closer to the table 11 at the upper limit position h1 to the switching position h2 (an example of an area other than the processing setting area set for bending the workpiece), the constant capacity type bidirectional pump 41 By supplying the oil from the above to only the second extension chamber 24 without supplying it to the first extension chamber 23, the area affected by the hydraulic pressure when the hydraulic cylinders 13a and 13b are extended can be reduced. Therefore, the ram 12 can be brought closer to the table 11 at high speed at the upper limit position h1 to the switching position h2. A region other than the machining setting region in such an approach can be said to be a high-speed approach region.

Further, by supplying oil to the first extension chamber 23, oil is supplied to both the first extension chamber 23 and the second extension chamber 24 in the processing setting area, and the hydraulic cylinders 13a and 13b are extended. The area actuated by the hydraulic pressure can be increased. Therefore, the ram 12 can be brought closer to the table 11 by increasing the pressing force at a low speed in the machining setting region. The processing region in such an approach can be said to be a low-speed approach region.

That is, the ram 12 approaches the table 11 only by changing the state in which oil is supplied only to one of the two extension chambers 23 and 24 to the state in which oil is supplied to both extension chambers 23 and 24. Since the speed can be changed from high speed to low speed and the pressing force can be increased, it is possible to perform the same efficient ram operation without using a complicated bidirectional pump and system to make the discharge amount variable.

Further, the machining setting region (low-speed approach region) may be an region in which the die 17 and the punch 18 actually come into contact with the work W and the plate-shaped member is bent, or the die 17 and the punch 18 are actually punched. 18 may be a region including a region where the plate-shaped member is bent in contact with the work W. That is, the switching position h2 may be a position where the punch 18 contacts the work W, or may be set at a position higher than the position where the punch 18 contacts the work W.

<4. Other embodiments>
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention.
(A)
In the above embodiment, the relief valve 74 is used as an example of the resistance generating unit, but the relief valve 74 is not limited to this, and an accumulator may be provided, for example. In short, it is only necessary to exert a counter force capable of suppressing the ram 12 from falling under its own weight.

(B)
In the above embodiment, the table 11 which is an example of the fixed table is arranged at the lower side, and the ram 12 which is an example of the movable table is arranged at the upper side, but it may be reversed. That is, the movable table may be arranged below the fixed table so that the movable table rises to approach the fixed table and the movable table descends to separate from the fixed table.

(C)
In the above embodiment, an on-off valve 64 is provided as an example of the shutoff portion, the supply of oil from the constant-capacity bidirectional pump 41 to the first extension chamber 23 is cut off in the high-speed approach region, and the first in the low-speed approach region. Oil is supplied from the constant-capacity bidirectional pump 41 to both the extension chamber 23 and the second extension chamber 24, but the present invention is not limited to this. For example, when entering the low-speed approach region from the high-speed approach region (that is, the switching position h2), the oil supply from the constant-capacity bidirectional pump 41 is switched from the second extension chamber 24 to the first extension chamber 23. A switching valve or the like may be provided as an example of the shutoff portion. That is, in the high-speed approach region, oil may be supplied from the constant-capacity bidirectional pump 41 only to the first extension chamber 23. Even in this case, since the cross-sectional area of the first extension chamber 23 perpendicular to the expansion / contraction direction is formed larger than the cross-sectional area of the second extension chamber 24 perpendicular to the expansion / contraction direction, the approach is high speed. The pressure can be increased in the area.

(D)
In the above embodiment, the cross-sectional area of the first extension chamber 23 perpendicular to the expansion / contraction direction is formed to be larger than the cross-sectional area of the second extension chamber 24 perpendicular to the expansion / contraction direction, but this is limited to this. It doesn't have to be. In the high-speed approach region, oil is supplied from the constant-capacity bidirectional pump 41 only to the second extension chamber 24, and in the low-speed approach region, oil is supplied to both the first extension chamber 23 and the second extension chamber 24. Even if the cross-sectional area of the first extension chamber 23 is equal to or less than the cross-sectional area of the second extension chamber 24, the pressure in the low-speed approach region can be made larger than that in the high-speed approach region.

However, if the cross-sectional area of the first extension chamber 23 is formed larger than the cross-sectional area of the second extension chamber 24, the constant-capacity bidirectional pump 41 approaches the high-speed approach region at a low speed even if the discharge amount is the same. It is efficient because the speed difference and pressure difference in the area can be increased.
(E)
In the hydraulic cylinders 13a and 13b of the above embodiment, the diameter of the sliding portion 34, which is the lower end portion of the rod-shaped member 22, is formed to be larger than the diameter of the rod portion 35, and the inner peripheral surfaces of the sliding portion 34 and the hole portion 33 are formed. The second extension chamber 24 is formed by contact with the two, but the present invention is not limited to this. For example, the hydraulic cylinder 13a'having the configuration shown in FIGS. 7 (a) and 7 (b) may be used. FIG. 7A is a diagram showing a state in which the hydraulic cylinder 13a'is contracted. FIG. 7B is a diagram showing a state in which the hydraulic cylinder 13a'is extended.

Unlike the rod-shaped member 22 of the above-described embodiment, the rod-shaped member 22'of the hydraulic cylinder 13a'shown in FIGS. 7 (a) and 7 (b) is not provided with the sliding portion 34. Further, unlike the piston portion 21 of the above embodiment, the piston portion 21' has a protruding portion 37 formed so as to project inward in the radial direction from the entire circumference of the upper end portion of the inner peripheral surface of the hole portion 33. It is provided.
The protruding portion 37 is in contact with the entire circumference of the outer peripheral surface of the rod-shaped member 22', whereby the second extension chamber 24 is formed. As shown in FIGS. 7 (a) and 7 (b), when the hydraulic cylinder 13a'expands and contracts, the piston portion 21'moves up and down while sliding with respect to the rod-shaped member 22'at the protruding portion 37. .. The hydraulic cylinder 13b may also have the same configuration as the hydraulic cylinder 13a'shown in FIGS. 7 (a) and 7 (b).

(F)
In the above embodiment, the constant capacity type bidirectional pump 41 is used as an example of the pump, but the present invention is not limited to this. For example, a variable displacement pump may be used, and even in that case, the speed of the ram 12 can be changed by controlling the supply of oil to the two extension chambers 23 and 24, so that the amount of oil can be adjusted by the pump. Can be reduced and control becomes easier.

The press brake and bending method of the present invention can be stably operated by simple control, and can be widely applied to bending of plate materials.

1: Press brake 10: Frame 10a: Plate part 10b: Plate part 11: Table (example of fixed table)
12: Ram (an example of a movable table)
13a: Hydraulic cylinder 13a': Hydraulic cylinder 13b: Hydraulic cylinder 14a: Cylinder drive unit 14b: Cylinder drive unit 15: Control unit 16: Operation unit 17: Die 18: Punch 20: Cylinder tube 20a: Bottom surface 21: Piston unit 21' : Piston portion 22: Rod-shaped member 22': Rod-shaped member 23: First extension chamber 24: Second extension chamber 25: Shrink chamber 31: Piston 31a: Opening 31b: Upper surface 31c: Lower surface 32: Piston rod 33: Hole 33a : Bottom surface 34: Sliding part 35: Rod part 36: Cylinder flow passage 36a: Opening part 37: Protruding part 40: Hydraulic circuit 41: Bidirectional pump (an example of a pump)
41a: 1st discharge part 41b: 2nd discharge part 42: Servo motor 43: Tank 51: 1st main circuit 52: 2nd main circuit 53: Oil amount replenishment circuit 54: 1st extension chamber oil amount adjustment circuit 61: First 1st flow passage 62: 2nd flow passage 63: 3rd flow passage 64: Open / close valve (an example of a blocking part)
71: 4th flow passage 72: Check valve 73: 5th flow passage 74: Relief valve (example of resistance generating part, example of valve)
75: Stop valve 81: Prefill valve 82: Control valve 83: 6th flow passage 84: 7th flow passage 91a: Confluence portion 91b: Confluence portion 92: Pressure sensor 93: Linear sensor 94: Operation panel 95: Foot switch 96 : Servo amplifier W: Work (example of plate-shaped member)
h1: Upper limit position h2: Switching position h3: Lower limit position

Claims (8)

A press brake that bends plate-shaped members with punches and dies.
A movable table on which the punch is mounted and
A fixed table on which the die is mounted and
It has a first extension chamber and a second extension chamber to which oil is supplied when expanding, and a contraction chamber to which oil is supplied when contracting, and the movable table approaches the fixed table by expansion and contraction. Or with a hydraulic cylinder to separate
It has a first discharge portion connected to the first extension chamber and the second extension chamber, and a second discharge portion connected to the contraction chamber, and of the first discharge portion and the second discharge portion. When discharging oil from one of them, a pump that sucks oil from the other,
An on-off valve provided in the first flow path connecting between the first discharge portion and the first extension chamber and capable of blocking the flow of oil,
A prefill valve provided in a second flow path connecting the first extension chamber and a tank in which oil is stored,
A control valve provided in a third flow path connecting the second discharge portion and the contraction chamber and a fourth flow path connecting the prefill valve.
The opening / closing valve, the control valve, and a control unit for controlling the pump are provided.
When the pressure oil is not supplied through the control valve, the prefill valve enables the oil of the tank to be supplied to the first extension chamber through the second flow path, and the pressure oil is supplied through the control valve. Is supplied, the oil in the first extension chamber can be discharged to the tank through the second flow path.
The control unit
The control valve shuts off the fourth flow path, the on-off valve shuts off the first flow path, and the oil discharged from the first discharge portion of the pump is supplied to the second extension chamber. , The movable table is brought close to the fixed table up to the first predetermined position.
When the movable table reaches the first predetermined position, the on-off valve enables the flow of oil in the first flow path, and the oil discharged from the first discharge portion of the pump is discharged from the first extension chamber. And the movable table is brought close to the fixed table to the second predetermined position by supplying the second extension chamber.
When the movable table reaches the second predetermined position, the on-off valve shuts off the first flow path and the control valve opens the fourth flow path to supply pressure oil to the prefill valve. The oil discharged from the second discharge portion of the pump is supplied to the shrink chamber to separate the movable table from the fixed table.
Press brake. Further provided with a resistance generating portion that generates resistance against the discharge of oil from the hydraulic cylinder due to the lowering of the movable table.
The press brake according to claim 1. The resistance generating part is
It is connected to the contraction chamber and has a valve that shuts off oil when the oil pressure is less than a predetermined value and allows oil to pass when the oil pressure is equal to or more than the predetermined value.
The press brake according to claim 2. The hydraulic cylinder
Cylinder tube and
It has a piston portion that is inserted into the cylinder tube and can slide on the inner peripheral surface of the cylinder tube.
The area of the first surface of the piston portion forming the second extension chamber, which is perpendicular to the expansion and contraction direction, is perpendicular to the expansion and contraction direction of the surface of the piston portion forming the contraction chamber. Same as the area of the second surface,
The press brake according to claim 1. The hydraulic cylinder
It further has a rod-shaped member inserted into a hole formed in the piston portion so as to follow the expansion / contraction direction.
The piston part
A piston rod that is inserted into the cylinder tube so that the longitudinal direction follows the expansion / contraction direction and whose tip is connected to the movable table.
It has a piston that is fixed to the piston rod and can slide on the inner peripheral surface of the cylinder tube.
The hole is formed from an opening provided in the piston to the piston rod, and the end of the hole on the piston rod side is closed.
The rod-shaped member is
At its tip, it has a sliding portion that can slide with respect to the inner peripheral surface of the hole.
The second extension chamber is formed by a space inside the hole portion and surrounded by the rod-shaped member and the piston portion.
The first extension chamber is formed by a space surrounded by the piston portion, the rod-shaped member, and the cylinder tube.
The contraction chamber is formed by a space surrounded by the piston portion and the cylinder tube.
The first surface is a portion of the surface of the piston rod facing the second extension chamber that faces the sliding portion.
The second surface is a surface portion of the piston facing the contraction chamber.
The press brake according to claim 4. The pump is a constant-capacity bidirectional pump.
The press brake according to claim 1. Further equipped with an electric servomotor for driving the pump,
The press brake according to claim 1. It is a bending method that bends a plate-shaped member.
A punch is attached by discharging oil from the first discharge portion of the pump to supply oil to the second extension chamber of the hydraulic cylinder and sucking oil from the contraction chamber of the hydraulic cylinder to the second discharge portion of the pump. The first approach step to bring the movable table closer to the fixed table on which the die is mounted,
By discharging oil from the first discharge portion of the pump to supply the oil to the first extension chamber and the second extension chamber, and sucking the oil from the contraction chamber to the second discharge portion of the pump. A second approach step of bringing the movable table closer to the fixed table,
The oil is discharged from the second discharge portion of the pump to supply the oil to the contraction chamber, and the oil is sucked from the first extension chamber of the hydraulic cylinder to the first discharge portion of the pump. e Bei and spaced steps to separate the movable table from said fixed table,
An on-off valve capable of blocking the flow of oil is provided in the first flow path connecting the first discharge portion and the first extension chamber.
A prefill valve is provided in the second flow path connecting the first extension chamber and the tank in which oil is stored.
A control valve is provided in the third flow path connecting the second discharge portion and the contraction chamber and the fourth flow path connecting the prefill valve.
When the pressure oil is not supplied through the control valve, the prefill valve enables the oil of the tank to be supplied to the first extension chamber through the second flow path, and the pressure oil is supplied through the control valve. Is supplied, the oil in the first extension chamber can be discharged to the tank through the second flow path.
In the first approach step, the control valve shuts off the fourth flow path, and the on-off valve shuts off the first flow path.
In the second approach step, the on-off valve enables the flow of oil in the first flow path.
In the separation step, the opening / closing valve shuts off the first flow path, and the control valve opens the fourth flow path, so that pressure oil can be supplied to the prefill valve.
Bending method.

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