Bending machine, and bending machine table control method

Abstract

To perform elevation control of a movable table taking action due to a self-weight of the movable table into consideration.SOLUTION: A press brake 1 has: an upper table 7 which is so located as to face a lower table 5 in a vertical direction; a drive unit 24 including a drive shaft 41 to which power from a motor 25 for driving is transmitted via a plurality of gear elements; a ball screw mechanism 55 which converts rotational motion of the drive shaft 41 into linear motion along the vertical direction; a brake mechanism 70 which gives a force resisting a force for moving the upper table 7 in a lower direction; and a control unit 100 which performs elevation control of the upper table 7 for bending a work-piece. The control unit 100 switches the brake mechanism 70 on and off according to a control process in the elevation control of the upper table 7.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bending machine and a method for controlling a table of the bending machine. [Background technology]

[0002] A press brake performs bending processing on a workpiece by moving a movable table, on which a mold such as a punch is mounted, in the vertical direction relative to a fixed table, on which a mold such as a die is mounted. The table drive device that drives the movable table includes a drive unit that rotates a drive shaft by a drive motor, and a conversion unit that converts the rotational motion of the drive shaft into linear motion along the vertical direction to move the movable table in the vertical direction. The drive unit includes multiple gear elements that can be engaged with each other by a tooth structure, and power from the drive motor is transmitted to the drive shaft via the multiple gear elements.

[0003] Patent Document 1 discloses a technique in which a ball screw mechanism is rotated by a rotary drive source to move a movable table in the up and down direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5531878 Summary of the Invention [Problem to be solved by the invention]

[0005] In bending machines, it is necessary to control the elevation of the movable table, but the weight of the movable table, which is a heavy object, affects various control problems. Therefore, in order to control the elevation of the movable table, it is necessary to fully consider the effects of the movable table's weight. [Means for solving the problem]

[0006] A bending machine of one embodiment of the present invention has a movable table arranged opposite to a fixed table in the vertical direction, a drive unit including a drive motor, a plurality of gear elements engageable with each other by a tooth structure, and a drive shaft to which power from the drive motor is transmitted via the plurality of gear elements, a conversion unit that moves the movable table in the vertical direction by converting the rotational motion of the drive shaft into linear motion along the vertical direction, a brake mechanism that applies a force that resists the force moving the movable table downward, and a control device that controls the drive unit to control the raising and lowering of the movable table to perform bending processing on a workpiece, and the control device switches the brake mechanism on and off depending on the control process in controlling the raising and lowering of the movable table. Effect of the Invention

[0007] According to one aspect of the present invention, by switching the brake mechanism on and off, it is possible to control the elevation of the movable table while taking into account the effect of the movable table's own weight. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a side view showing a main part of a table drive device of a press brake according to this embodiment. [Diagram 2] FIG. 2 is a front view showing the overall configuration of the press brake according to this embodiment. [Diagram 3] FIG. 3 is a cross-sectional view showing a main part of the reducer. [Figure 4] FIG. 4 is an enlarged side view showing a main part of the clutch mechanism in the high speed mode. [Diagram 5] FIG. 5 is an enlarged side view showing a main part of the clutch mechanism in the high torque mode. [Figure 6] FIG. 6 is an explanatory diagram showing a modified example of the brake mechanism. [Figure 7] FIG. 7 is a diagram for explaining a series of steps in controlling the elevation of the upper table. [Figure 8]FIG. 8 is a diagram showing changes in speed, torque and pressure when the upper table descends in high torque mode, and is a diagram showing the state when the brake mechanism is not turned on. [Figure 9] FIG. 9 is a diagram showing changes in speed, torque and pressure when the upper table descends in high torque mode, with the brake mechanism turned on. [Figure 10] FIG. 10 is a diagram showing changes in speed, torque and pressure when the upper table descends in high torque mode, with the brake mechanism turned on. [Figure 11] FIG. 11 is a diagram showing the state of the clutch mechanism when the mode is switched from the high speed mode to the high torque mode. [Figure 12] FIG. 12 is a diagram illustrating the sudden stop of the upper table. [Figure 13] FIG. 13 is a diagram showing changes in speed and torque when the upper table is suddenly stopped, and is a diagram showing the state when the brake mechanism is not turned on. [Figure 14] FIG. 14 is a diagram showing changes in speed and torque when the upper table is suddenly stopped and the brake mechanism is turned on. [Figure 15] FIG. 15 is a diagram showing changes in speed and torque when the upper table descends from the upper end position, and is a diagram showing the state when the brake mechanism is not turned on. [Figure 16] FIG. 16 is a diagram showing changes in speed and torque when the upper table descends from the upper end position, and is a diagram showing the state when the brake mechanism is turned on. [Figure 17] FIG. 17 is a diagram for explaining a series of steps in controlling the elevation of the upper table. [Figure 18] FIG. 18 is a diagram showing the state of the clutch mechanism when the upper table is inverted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, with reference to the drawings, a bending machine according to this embodiment will be described using a press brake as an example.

[0010] 1 is a side view showing a main part of a table drive device 20 of a press brake 1 according to this embodiment. In this specification, the left-right direction, the front-rear direction, and the up-down direction are used as definitions of directions. The left-right direction and the front-rear direction correspond to two directions perpendicular to the horizontal direction, and the up-down direction corresponds to the vertical direction. These directions are merely used for convenience in explaining the press brake according to this embodiment.

[0011] The press brake 1 according to this embodiment includes an upper table 7 arranged to face the lower table 5 in the vertical direction, a drive unit 24 including a drive motor 25, a plurality of gear elements that can be engaged with each other by a tooth structure, and a drive shaft 41 to which the power from the drive motor 25 is transmitted via the plurality of gear elements, a ball screw mechanism 55 that converts the rotational motion of the drive shaft 41 into a linear motion along the vertical direction to move the upper table 7 in the vertical direction, a brake mechanism 70 that applies a force that resists the force that moves the upper table 7 downward, and a control device 100 that controls the drive unit 24 to control the lifting and lowering of the upper table 7 to perform bending processing on a workpiece. The control device 100 switches the brake mechanism 70 on and off depending on the control process in the lifting and lowering control of the upper table 7.

[0012] Hereinafter, the press brake 1 will be described in detail with reference to Figures 1 and 2. Figure 2 is a front view showing the overall configuration of the press brake 1 according to this embodiment.

[0013] 2, the press brake 1 performs bending processing on a plate-shaped workpiece such as sheet metal through cooperation between an upper tool P such as a punch and a lower tool D such as a die. The press brake 1 includes left and right side plates 2, a lower table 5 which is a fixed table, an upper table 7 which is a movable table, left and right table driving devices 20, and a control device 100.

[0014] The left and right side plates 2 are disposed opposite each other and spaced apart in the left-right direction.

[0015] The lower table 5 extends in the left-right direction and is supported by the front lower parts of the left and right side plates 2. A lower die holder 6 for detachably holding a lower die D is provided above the lower table 5 along the left-right direction.

[0016] The upper table 7 extends in the left-right direction and is supported on the front upper parts of the left and right side plates 2 so as to face the lower table 5. The upper table 7 is configured to be movable in the up-down direction relative to the left and right side plates 2. An upper die holder 8 that detachably holds an upper die P is provided below the upper table 7 along the left-right direction.

[0017] The left and right table drive devices 20 are fixed to the upper parts of the left and right side plates 2, respectively. Each table drive device 20 is a drive device that moves the upper table 7 in the vertical direction. As shown in FIG. 1, the table drive device 20 is mainly composed of a drive unit 24, a ball screw mechanism 55, and a brake mechanism 70.

[0018] The drive unit 24 drives the ball screw mechanism 55. The drive unit 24 is made up of a drive motor 25 and a reduction gear unit 30.

[0019] The driving motor 25 is a driving source that is driven by electric energy, and includes a driving motor shaft 26 (see FIG. 3) that rotates about an axis line. The driving motor 25 is, for example, a servo motor.

[0020] The reduction gear unit 30 includes a plurality of gear elements that are mutually engageable by a tooth structure, and a drive shaft 41 to which power from the drive motor 25 is transmitted via the plurality of gear elements. Due to the action of the plurality of gear elements, the rotation of the drive shaft 41 of the reduction gear unit 30 is reduced at a predetermined reduction ratio relative to the rotation of the drive motor shaft 26. Details of the reduction gear unit 30 will be described later. In the following description, the drive shaft 41 of the reduction gear unit 30 will also be referred to as the drive shaft 41 of the drive unit 24 as necessary.

[0021] The ball screw mechanism 55 is a conversion unit that converts the rotational motion of the drive shaft 41 of the drive unit 24 into linear motion, thereby moving the upper table 7 in the vertical direction. The ball screw mechanism 55 includes a ball screw nut 56 and a ball screw shaft 57. The ball screw nut 56 is supported inside the housing of the ball screw mechanism 55 via a bearing portion. The ball screw nut 56 is connected to the drive shaft 41 of the drive unit 24, and rotates in response to the rotation of the output portion. The ball screw shaft 57 is screwed into the ball screw nut 56, and moves in the vertical direction as the ball screw nut 56 rotates forward and backward.

[0022] The drive unit 24 and the ball screw mechanism 55 are arranged side by side in the front-rear direction so that the drive shaft 41 (rotation shaft) of the drive unit 24 and the ball screw nut 56 (rotation shaft) of the ball screw mechanism 55 are parallel to each other. The drive shaft 41 of the drive unit 24 and the ball screw nut 56 of the ball screw mechanism 55 are connected by a timing belt 43, and power is transmitted via this timing belt 43.

[0023] A connection block 60 is connected to the lower end of the ball screw mechanism 55, specifically the lower end of the ball screw shaft 57. A hanging bolt 61 hanging down in the vertical direction is attached to the lower end of the connection block 60, and the hanging bolt 61 supports a support shaft 62 penetrating the upper table 7 in the front-rear direction. The ball screw shaft 57 is connected to the upper table 7 via the connection block 60 including the hanging bolt 61 and the support shaft 62. In other words, the connection block 60 connects the ball screw mechanism 55 and the upper table 7, and moves the upper table 7 in the vertical direction by the vertical linear motion of the ball screw mechanism 55.

[0024] As shown in FIG. 1, the brake mechanism 70 is mainly composed of a brake motor 71 and a timing belt 73. The brake motor 71 is, for example, a servo motor. The brake motor 71 is provided with a motor drive circuit (not shown). When the brake signal supplied from the control device 100 is on, that is, when the brake mechanism 70 is instructed to be on, the motor drive circuit shorts the terminals (phases) of the motor via a resistor. This short circuit causes the rotational energy of the drive shaft 41 of the brake motor 71 to be consumed as heat by the resistor, and a braking force that stops the rotation of the brake motor shaft 72 is generated. On the other hand, when the brake signal is off, that is, when the brake mechanism 70 is instructed to be off, the motor drive circuit does not perform the above control. In this case, no braking force is generated in the brake motor shaft 72.

[0025] The timing belt 73 is stretched between the brake motor shaft 72 and the drive shaft 41 of the drive unit 24 .

[0026] The brake mechanism 70 having such a structure is called a dynamic brake. When the upper table 7 moves downward, the brake mechanism 70 is turned on, and the braking force of the brake motor 71 acts as a resistance on the drive shaft 41 of the drive unit 24. In other words, the drive unit 24 is given a force that resists the force that moves the upper table 7 downward.

[0027] A control device 100 such as an NC (Numerical Control) device that controls the operation of the press brake 1 is supported via a connection arm on the left side plate 2. The control device 100 controls the drive unit 24, the brake mechanism 70, and the like.

[0028] The reduction gear unit 30 will be described with reference to Figs. 3 to 5. Fig. 3 is a cross-sectional view showing the main parts of the reduction gear unit 30. Fig. 4 is an enlarged side view showing the main parts of the clutch mechanism 45, showing the state of the high-speed mode. Fig. 5 is an enlarged side view showing the main parts of the clutch mechanism 45, showing the state of the high-torque mode. For convenience of explanation, the reduction gear unit 30 shown in Fig. 3 is drawn upside down compared to the state of the reduction gear unit 30 shown in Fig. 1. Also, the clutch mechanism 45 shown in Figs. 4 and 5 is drawn based on the clutch mechanism 45 shown in Fig. 3 (the same applies below).

[0029] 3, the reduction gear unit 30 is composed of a reduction gear 31 and a clutch mechanism 45. The reduction gear 31 reduces the rotation of the drive motor shaft 26 at either a first reduction ratio or a second reduction ratio that is greater than the first reduction ratio, and outputs the reduced rotation to the drive shaft 41. The clutch mechanism 45 switches the reduction ratio of the reduction gear 31 between the first reduction ratio and the second reduction ratio.

[0030] The speed reducer 31 includes a paradox planetary gear mechanism. Specifically, the speed reducer 31 includes a sun gear 32, a plurality of planetary gear units 33, a planet carrier 34, a first internal gear 38, a second internal gear 40, and a drive shaft 41.

[0031] The sun gear 32 is fitted onto the outer circumferential surface of the drive motor shaft 26. The sun gear 32 rotates integrally with the drive motor shaft 26.

[0032] The planetary gear units 33 are provided around the sun gear 32 and are arranged at equal intervals in the circumferential direction. Each planetary gear unit 33 is composed of a first planetary gear 33a and a second planetary gear 33b. The first planetary gear 33a meshes with the sun gear 32 and rotates with the rotation of the sun gear 32. The second planetary gear 33b is provided coaxially with the first planetary gear 33a and rotates integrally with the first planetary gear 33a. In this embodiment, the first planetary gear 33a and the second planetary gear 33b have a two-stage structure integrated in the vertical direction, and the first planetary gear 33a and the second planetary gear 33b rotate on the same axis.

[0033] The planetary carrier 34 rotates around the drive motor shaft 26 via a bearing portion 35 fitted onto the outside of the drive motor shaft 26. A plurality of unit shafts 36 are provided along the circumferential direction on the planetary carrier 34. A bearing portion 37 is fitted onto each of the unit shafts 36, and the planetary gear units 33 are attached via the bearing portions 37. The planetary carrier 34 supports the plurality of planetary gear units 33 so that each can rotate on its own axis.

[0034] The first internal gear 38 is an internal gear that meshes with the first planetary gear 33a. The first internal gear 38 is provided on the inner circumferential surface of the housing of the reduction gear unit 30 via a bearing portion 39, and can rotate about the drive motor shaft 26.

[0035] The second internal gear 40 is an internal gear that has a different number of teeth from the first internal gear 38 and meshes with the second planetary gear 33b. The second internal gear 40 is provided on the inner circumferential surface of the housing of the reduction gear unit 30 via a bearing portion 42, and can rotate around the drive motor shaft 26.

[0036] The drive shaft 41 is formed integrally with the second internal gear 40, and rotates integrally with the second internal gear 40. The drive shaft 41 is connected to the ball screw nut 56 of the ball screw mechanism 55 described above.

[0037] The clutch mechanism 45 includes fixed clutch teeth 46, first clutch teeth 47, and second clutch teeth 48. The fixed clutch teeth 46, the first clutch teeth 47, and the second clutch teeth 48 are each annular members, and are formed with a tooth structure as described below. The first clutch teeth 47 and the second clutch teeth 48 are disposed facing each other vertically so that their tooth structures face each other. The fixed clutch teeth 46 are provided between the first clutch teeth 47 and the second clutch teeth 48.

[0038] As shown in Figures 4 and 5, the fixed clutch teeth 46 move between the first clutch teeth 47 and the second clutch teeth 48. The movement of the fixed clutch teeth 46 is restricted in any direction other than the up and down direction. The fixed clutch teeth 46 are provided with a plurality of first engagement teeth 46a arranged along the circumferential direction, and a plurality of second engagement teeth 46b arranged along the circumferential direction. Each of the first engagement teeth 46a protrudes toward the first clutch teeth 47 side, and each of the second engagement teeth 46b protrudes toward the second clutch teeth 48 side.

[0039] The first clutch teeth 47 are connected to the first internal gear 38 included in the reducer 31 and rotate integrally with the first internal gear 38 (see FIG. 3). The first clutch teeth 47 are provided with a plurality of third engagement teeth 47a arranged along the circumferential direction. Each of the third engagement teeth 47a protrudes toward the fixed clutch teeth 46.

[0040] The second clutch teeth 48 are connected to the planet carrier 34 included in the reduction gear 31 and rotate integrally with the planet carrier 34 (see FIG. 3). The second clutch teeth 48 are provided with a plurality of fourth engagement teeth 48a arranged along the circumferential direction. Each of the fourth engagement teeth 48a protrudes toward the fixed clutch teeth 46.

[0041] As shown in Fig. 3, the clutch mechanism 45 includes a pressing member (not shown) and a solenoid 49. The pressing member is, for example, a compression coil spring, and presses the fixed clutch teeth 46 toward the first clutch teeth 47. That is, the fixed clutch teeth 46 are subjected to the pressing force of the pressing member and normally move toward the first clutch teeth 47. On the other hand, the solenoid 49 moves the fixed clutch teeth 46 toward the second clutch teeth 48 by attracting them with electromagnetic force. That is, when the solenoid 49 is operated and attracted by electromagnetic force, the fixed clutch teeth 46 move toward the second clutch teeth 48 against the pressing force of the pressing member.

[0042] The fixed clutch teeth 46 have at least two switchable operating modes, including a high torque mode and a high speed mode.

[0043] 4, the high speed mode is a mode in which the fixed clutch teeth 46 mesh only with the second clutch teeth 48. The fixed clutch teeth 46 mesh with the second clutch teeth 48, thereby fixing the second clutch teeth 48 and restricting the rotation of the planetary carrier 34. In this case, the reducer 31 operates at a reduction ratio (first reduction ratio) smaller than the second reduction ratio.

[0044] 5, the high torque mode is a mode in which the fixed clutch teeth 46 mesh only with the first clutch teeth 47. The fixed clutch teeth 46 mesh with the first clutch teeth 47, thereby fixing the first clutch teeth 47 and restricting the rotation of the first internal gear 38. In this case, the reducer 31 operates at a large reduction ratio (second reduction ratio).

[0045] The press brake 1 is configured as described above. In the above embodiment, an example of a dynamic brake is shown as the brake mechanism 70. However, the brake mechanism 70 is not limited to this, and may be any mechanism that applies a force to the drive unit 24 that resists a force that moves the upper table 7 downward.

[0046] FIG. 6 is an explanatory diagram showing a modified example of the brake mechanism 70. The brake mechanism 70 according to the modified example is mainly composed of an air cylinder 75 and an electromagnetic valve (not shown). The air cylinder 75 is an air-pressure operated actuator, and is an example of a fluid pressure cylinder. A piston that can slide vertically is provided inside the air cylinder 75. A rod 76 is connected to the piston. The rod 76 advances and retreats in response to the movement of the piston. The air cylinder 75 is fixed to the upper frame 3 that straddles the left and right side plates 2 via a fixing member 77. The upper end of the rod 76 is fixed to the upper table 7 via a fixing member 78.

[0047] The solenoid valve controls the supply and discharge of air to and from the air cylinder 75 in response to a brake signal supplied from the control device 100 (supply / discharge control). When the brake signal supplied from the control device 100 is on, the solenoid valve performs a first supply / discharge control. In accordance with this first supply / discharge control, the air cylinder 75 generates a force Fc that lifts the upper table 7 upward via the rod 76. On the other hand, when the brake signal is off, the solenoid valve performs a second supply / discharge control. In the case of this second supply / discharge control, the air cylinder 75 does not generate the above-mentioned force Fc, and allows the rod 76 to move freely.

[0048] According to the brake mechanism 70 having such a structure, when the brake mechanism 70 is turned on, an upward force Fc acts on the upper table 7. Therefore, this upward force Fc acts on the drive unit 24 as a force that resists the force that moves the upper table 7 downward.

[0049] Below, the control of lifting and lowering the upper table 7 for bending the workpiece will be described with reference to Fig. 7. Fig. 7 is a diagram for explaining a series of steps in the control of lifting and lowering the upper table. When processing the workpiece using the press brake 1, the workpiece is first positioned on the lower die D. At this time, the upper table 7 is supported at a predetermined upper end position P1.

[0050] The control device 100 performs an attraction operation on the solenoid 49. As a result, the fixed clutch teeth 46 move toward the second clutch teeth 48, and the high speed mode is established in which the fixed clutch teeth 46 mesh only with the second clutch teeth 48 (FIG. 4).

[0051] The control device 100 rotates the drive motor shaft 26 forward. In the high-speed mode, the planetary carrier 34 is fixed, but the first internal gear 38 is released. Since the planetary carrier 34 is fixed, the first planetary gear 33a meshing with the first internal gear 38 does not revolve, but rotates on its axis in accordance with the rotation of the sun gear 32 that rotates integrally with the drive motor shaft 26. On the other hand, the rotation of the first planetary gear 33a also rotates the second planetary gear 33b that is integral with it, so that the second internal gear 40 also rotates due to the rotation of the second planetary gear 33b. As a result, the drive shaft 41 connected to the second internal gear 40 also rotates in synchronization. At this time, the rotation of the drive motor shaft 26 is output to the drive shaft 41 as a simple planetary gear mechanism without being decelerated by the paradox planetary gear mechanism. In other words, the reduction ratio of the reducer 31 becomes the first reduction ratio. Therefore, the drive shaft 41 rotates at high speed and low torque, and the upper table 7 descends at high speed.

[0052] When the upper table 7 descends to the low-speed switching position P2, the control device 100 stops the rotation of the drive motor shaft 26. After that, the control device 100 ends the suction operation of the solenoid 49. As a result, the fixed clutch teeth 46 move toward the first clutch teeth 47, and the fixed clutch teeth 46 enter the high torque mode in which they mesh only with the first clutch teeth 47 (FIG. 5).

[0053] The control device 100 rotates the drive motor shaft 26 in the reverse direction. In the high torque mode, the first internal gear 38 is fixed, but the planetary carrier 34 is released. Therefore, the first planetary gear 33a meshing with the first internal gear 38 rotates on its own axis while revolving around the sun gear 32 that rotates integrally with the drive motor shaft 26. The rotation of the first planetary gear 33a also rotates the second planetary gear 33b that is integral with it, and the rotation of the second planetary gear 33b also rotates the second internal gear 40 that has a different number of teeth from the first internal gear 38. As a result, the drive shaft 41 coupled to the second internal gear 40 also rotates in synchronization. At this time, the rotation of the drive motor shaft 26 is significantly reduced by the paradox planetary gear mechanism and is output to the drive shaft 41. That is, the reduction ratio of the reducer 31 becomes a second reduction ratio that is greater than the first reduction ratio. Therefore, the drive shaft 41 rotates at a low speed and with a high torque, and the upper table 7 descends at a low speed.

[0054] When the upper table 7 reaches a predetermined lower end position (stroke position) P3, the control device 100 stops the reverse rotation of the drive motor shaft 26 and keeps it stopped for a certain period of time. The workpiece is pressed between the upper die P and the lower die D and bent to the desired angle.

[0055] Next, the control device 100 rotates the drive motor shaft 26 in the forward direction. At this time, the rotation of the drive motor shaft 26 is significantly decelerated by the paradox planetary gear mechanism and output to the drive shaft 41. As a result, the upper table 7 rises at a low speed.

[0056] When the upper table 7 rises to a predetermined high speed switching position P4, the control device 100 stops the rotation of the drive motor shaft 26. After that, the control device 100 causes the solenoid 49 to perform an adsorption operation. As a result, the fixed clutch teeth 46 move toward the second clutch teeth 48, and the high speed mode is entered in which the fixed clutch teeth 46 mesh only with the second clutch teeth 48.

[0057] The control device 100 rotates the drive motor shaft 26 in the reverse direction. At this time, the rotation of the drive motor shaft 26 is output to the drive shaft 41 as a simple planetary gear mechanism without being decelerated by the paradox planetary gear mechanism. As a result, the upper table 7 rises at high speed. When the upper table 7 moves to the upper end position P1, the control device 100 stops the rotation of the drive motor shaft 26 and ends the suction operation of the solenoid 49.

[0058] As described above, in the press brake 1, bending of the workpiece is performed through a series of processes in controlling the elevation of the upper table 7.

[0059] One of the features of the press brake 1 according to this embodiment is that the brake mechanism 70 is switched on and off depending on the process of the control in the lifting and lowering control of the upper table 7. Specifically, the control device 100 turns on the brake mechanism 70 during each of the pressurization deceleration period Ta, the clutch switching period Tb, the table maintenance period Tc, and the sudden stop period Te (see FIG. 12). The operation of the brake mechanism 70 for each period will be described below.

[0060] <Pressure deceleration period Ta> The operation of the brake mechanism 70 during the pressurization and deceleration period Ta will be described with reference to Figs. 8 to 10. Figs. 8 to 10 are diagrams showing the transitions of speed, torque, and pressure when the upper table 7 descends in high torque mode. Of these, Fig. 8 is a diagram showing the case where the brake mechanism 70 is not turned on, and Figs. 9 and 10 are diagrams showing the case where the brake mechanism 70 is turned on. "Speed" indicates the speed of the upper table 7, "torque" indicates the torque of the drive motor 25, and "pressure" indicates the pressure acting on the upper table 7 (same below).

[0061] The pressurizing deceleration period Ta refers to a period during which the upper table 7 decelerates toward the lower end position P3 (see FIG. 7) while pressing the workpiece between the upper die P and the lower die D. As shown in FIG. 8, when the upper table 7 starts moving from the low-speed switching position P2 and descends at a constant speed, a torque (negative torque) in a direction pushing the upper table 7 downward acts on the driving motor 25. Then, as the upper table 7 approaches the lower end position P3, a deceleration torque acts, causing the upper table 7 to decelerate. At this time, as shown in region A in FIG. 8, the deceleration torque may appear on the positive side. The phenomenon in which the deceleration torque appears on the positive side is noticeable in (1) bending with a low load, such as bending a thin plate, and (2) offset bending in which one of the left and right drive shafts 41 is under a low load.

[0062] The reason why the deceleration torque appears on the positive side is that the frictional force of the gear elements constituting the drive unit 24 alone cannot support the weight of the upper table 7, which is a heavy object, and a force that tries to support the weight of the upper table 7 is generated in the drive motor 25. At this time, the gear elements rotate by the amount of the gap between the mutually engaged teeth, and the upper table 7 moves downward. For this reason, even if the control device 100 stops the drive unit 24 in accordance with the lower end position P3, a problem occurs in which the upper table 7 deviates from the lower end position P3. This problem is expected for various gear elements included in the drive unit 24, but below, it will be explained using the tooth structure of the clutch mechanism 45 as an example.

[0063] When the upper table 7 moves from the switching position P2 to the lower end position P3, the clutch mechanism 45 operates in the high torque mode. When a torque (negative torque) in a direction pushing the upper table 7 downward acts on the driving motor 25, the first clutch tooth 47 meshing with the fixed clutch tooth 46 pushes the fixed clutch tooth 46 in a direction toward the right in the figure, as shown in Fig. 5. On the other hand, when the torque of the driving motor 25 appears on the positive side, the force acting on the first clutch tooth 47 is reversed, and as a result, the first clutch tooth 47 moves by the amount of the gap Gp. This movement of the first clutch tooth 47 causes the upper table 7 to become misaligned.

[0064] Therefore, by turning on the brake mechanism 70 during the pressurization deceleration period Ta, as shown in FIG. 9, a force that resists the force that moves the upper table 7 downward is applied to the drive unit 24 during deceleration. The deceleration torque of the drive motor 25 has a component in the direction that pushes the upper table 7 downward. As shown in FIG. 5, a force toward the right side in the figure always acts on the first clutch tooth 47, so that the movement of the first clutch tooth 47 can be suppressed. This suppresses the positional deviation of the upper table 7, and allows the upper table 7 to be accurately positioned with respect to the lower end position P3.

[0065] As described above, cases in which torque appears on the positive side during deceleration are limited to certain machining conditions. Therefore, the control device 100 may turn on the brake mechanism 70 during the pressurization and deceleration period Ta only when certain execution conditions are satisfied. Therefore, when the execution conditions are not satisfied, that is, when the prohibition conditions are satisfied, the control device 100 may continue to keep the brake mechanism 70 off even during the pressurization and deceleration period Ta.

[0066] The control device 100 may determine whether the execution condition is satisfied based on the processing conditions. Also, as shown in Fig. 9, a pressure threshold Th serving as a judgment criterion is determined in advance. The control device 100 may determine that the execution condition is satisfied when the pressure acting on the upper table 7 does not reach the pressure threshold Th, and may determine that the prohibition condition is satisfied when the pressure acting on the upper table 7 exceeds the pressure threshold Th.

[0067] The period during which the brake mechanism 70 is turned on should include at least the pressurization deceleration period Ta. Therefore, as shown in Fig. 10, the brake mechanism 70 may be turned on a certain time before the timing to decelerate the upper table 7. Alternatively, the brake mechanism 70 may be turned on continuously for a certain time after the upper table 7 has stopped.

[0068] <Clutch switching period Tb> The operation of the brake mechanism 70 during the clutch switching period Tb will be described. The clutch switching period Tb is a period during which the fixed clutch teeth 46 are raised and lowered to switch the clutch mechanism 45. As shown in Fig. 7, the control device 100 switches the clutch mechanism 45 from the high-speed mode to the high-torque mode while the upper table 7 is being lowered from the upper end position P1 to the lower end position P3 (specifically, at the low-speed switching position P2). Similarly, the control device 100 switches the clutch mechanism 45 from the high-torque mode to the high-speed mode while the upper table 7 is being raised from the lower end position P3 to the upper end position P1 (specifically, at the high-speed switching position P4).

[0069] Fig. 11 is a diagram showing the state of the clutch mechanism 45 when switching from the high speed mode to the high torque mode. "State A1" in Fig. 11 shows the state of the clutch mechanism 45 before the mode switching. When the fixed clutch tooth 46 is transitioned to the high torque mode, depending on the positional relationship between the first clutch tooth 47 and the fixed clutch tooth 46, the tip of the third engagement tooth 47a of the first clutch tooth 47 may interfere with the tip of the first engagement tooth 46a of the fixed clutch tooth 46. A situation occurs in which the fixed clutch tooth 46 cannot be transitioned to the high torque mode.

[0070] Therefore, prior to switching from the high speed mode to the high torque mode, the control device 100 rotates the drive motor shaft 26 and controls the first clutch teeth 47 to rotate by a predetermined rotation angle in the direction R1. This causes a phase shift between the first clutch teeth 47 and the fixed clutch teeth 46, so that the tooth tips of the first engagement teeth 46a of the fixed clutch teeth 46 correspond to the spaces between the third engagement teeth 47a of the first clutch teeth 47 (state B1). As a result, the fixed clutch teeth 46 can be transitioned to the high torque mode.

[0071] However, while the first clutch tooth 47 is moving to the high torque mode, the frictional force of the components constituting the drive unit 24 alone cannot support the weight of the upper table 7, which is a heavy object, and the first clutch tooth 47 rotates. In this case, the tip of the third engagement tooth 47a of the first clutch tooth 47 may interfere with the tip of the first engagement tooth 46a of the fixed clutch tooth 46 (state C11). This reduces the success rate of mode switching by the clutch mechanism 45.

[0072] However, as shown in Fig. 9, the brake mechanism 70 is turned on during the clutch switching period Tb. This applies a force to the drive unit 24 that resists the force that moves the upper table 7 downward. Since the brake mechanism 70 bears the weight of the upper table 7, it is possible to suppress the rotation of the first clutch teeth 47 (state C12). This makes it possible to increase the success rate of mode switching by the clutch mechanism 45.

[0073] 11 shows the state of the clutch mechanism 45 when the mode is switched from the high speed mode to the high torque mode, but the same applies when the mode is switched from the high torque mode to the high speed mode. The period during which the brake mechanism 70 is turned on only needs to include at least the clutch switching period Tb. Therefore, the brake mechanism 70 may be turned on a certain time prior to the clutch switching period Tb, or may be turned on continuously for a certain time after the clutch switching period Tb.

[0074] <Emergency stop period Te> 12 is a diagram illustrating the sudden stop of the upper table 7. In controlling the elevation of the upper table 7, the control device 100 causes the upper table 7 to suddenly stop when a predetermined condition, such as an alarm, is triggered. At this time, the control device 100 may turn on the brake mechanism 70 during the sudden stop period Te during which the upper table 7 is suddenly stopped.

[0075] 13 and 14 are diagrams showing changes in speed and torque when the upper table 7 is suddenly stopped. Of these, Fig. 13 is a diagram showing the case where the brake mechanism 70 is not turned on, and Fig. 14 is a diagram showing the case where the brake mechanism 70 is turned on.

[0076] When the brake mechanism 70 is not used, the control device 100 can rapidly decelerate the upper table 7 by controlling the rotation of the drive motor 25, as shown in Fig. 13. However, when the brake mechanism 70 is turned on, the weight of the upper table 7 can be supported by the force generated by the brake mechanism 70. Therefore, the braking force generated by the drive motor 25 is assisted by the force of the brake mechanism 70. As a result, a large braking force is applied to the upper table 7, so that the upper table 7 can be stopped quickly.

[0077] The period during which the brake mechanism 70 is turned on should include at least the sudden stop period Te. Therefore, the brake mechanism 70 may be turned on continuously for a certain period of time after the sudden stop period Te.

[0078] The operation of the brake mechanism 70 during the table maintenance period Tc will be described with reference to Fig. 15 and Fig. 16. Here, Fig. 15 and Fig. 16 are diagrams showing the transition of the speed and torque when the upper table 7 descends from the upper end position P1. Of these, Fig. 15 is a diagram showing the case where the brake mechanism 70 is not turned on, and Fig. 16 is a diagram showing the case where the brake mechanism 70 is turned on.

[0079] The table maintenance period Tc is a period during which the upper table 7 is maintained at the upper end position P1 (see FIG. 7). When the brake mechanism 70 is not used, as shown in FIG. 15, in order to maintain the upper table 7 at the upper end position P1 (see FIG. 7), it is necessary to operate the drive motor 25 to generate a stationary torque for stopping the upper table 7. However, during the table maintenance period Tc, the brake mechanism 70 is turned on and generates a force, which makes it possible to support the weight of the upper table 7. This eliminates the need to operate the high-output drive motor 25, as shown in FIG. 16, and is therefore expected to result in power savings.

[0080] (Modification of Press Brake 1) FIG. 17 is a diagram for explaining a series of processes in the lift control of the upper table 7. There are various models of press brakes 1, some of which are equipped with a sensor unit that automatically measures the bending angle of the work. In a press brake equipped with such a sensor unit, after starting to pressurize the work, the upper table 7 is inverted upward before reaching the lower end position P3 to release the pressure on the work (unloading). Then, in a state in which springback occurs in the work, the bending angle of the work is measured by the sensor unit. The measured bending angle of the work is processed by the control device 100, and the lower end position P3 is corrected as necessary. Thereafter, the work is pressed according to the corrected lower end position P3.

[0081] When such a process of unloading is included, the control device 100 may turn on the brake mechanism 70 during the reversal period Tf, which is the period during which the upper table 7 is reversed.

[0082] 18 is a diagram showing the state of the clutch mechanism 45 when the upper table 7 is inverted. As shown in state A2, when the upper table 7 is being lowered, a force in the direction R2 acts on the first clutch tooth 47 as the driving motor 25 rotates.

[0083] On the other hand, since it is necessary to move the upper table 7 upward to release the pressure, the control device 100 reverses the rotation direction of the drive motor shaft 26 after stopping the rotation of the drive motor shaft 26. At this time, a force from the drive motor 25 in the direction R1 acts on the first clutch tooth 47, and the gap between the first clutch tooth 47 and the fixed clutch tooth 46 is closed (state B21). When the gap between the first clutch tooth 47 and the fixed clutch tooth 46 is closed, the upper table 7 starts to move.

[0084] On the other hand, if the brake mechanism 70 is on when the upper table 7 is reversed, a force that resists the force that moves the upper table 7 downward is applied to the drive unit 24. Therefore, the force generated by the brake mechanism 70 moves the first clutch tooth 47, and the gap between the first clutch tooth 47 and the fixed clutch tooth 46 is reduced. In other words, the gap between the first clutch tooth 47 and the fixed clutch tooth 46 can be reduced without receiving force from the drive motor 25 (state B22). This improves the responsiveness of the upper table 7 during the reverse operation.

[0085] When the brake mechanism is turned on in synchronization with the reversal of the movable table, the above-mentioned effect can be appropriately obtained by using a brake mechanism 70 using a fluid pressure cylinder as shown in Fig. 7. Also, the brake mechanism 70 may be turned on a certain period prior to the reversal period Tf of the upper table 7.

[0086] As described above, according to this embodiment, the upper table 7 can be controlled by fully considering the action of the weight of the upper table 7. As a result, as described above, unique effects can be obtained in each process. In addition, the table control method of the press brake 1 (bending machine) as described above also functions as a part of this embodiment.

[0087] As described above, the present embodiment has been described, but the description and drawings forming a part of this embodiment should not be understood as limiting this embodiment. Various alternative embodiments, examples and operation techniques will be apparent to those skilled in the art from this embodiment. [Explanation of symbols]

[0088] 1. Press brake 2 Side Plates 5 Lower table (fixed table) 7 Upper table (movable table) 20 Table drive unit 24 Drive unit 25 Drive motor 26 Drive motor shaft 30 Reduction gear unit 31 Reducer 41 Drive shaft 45 Clutch mechanism 46 fixed clutch teeth 47 1st clutch tooth 48 2nd clutch teeth 55 Ball screw mechanism (conversion unit) 56 Ball screw nut 57 Ball screw shaft 70 Brake Mechanism 71 Brake motor 72 Brake motor shaft 73 Timing belt 75 Air Cylinder 76 Rod 100 Control device

Claims

1. a movable table disposed opposite to the fixed table in the up-down direction; a drive unit including a drive motor, a plurality of gear elements that are engageable with each other by a tooth structure, and a drive shaft to which power from the drive motor is transmitted via the plurality of gear elements; a conversion unit that converts a rotational motion of the drive shaft into a linear motion along a vertical direction, thereby moving the movable table in a vertical direction; a brake mechanism that applies a force resisting a force that moves the movable table downward; a control device that controls the drive unit to control the elevation of the movable table for bending a workpiece, The control device of the bending machine switches on and off the brake mechanism depending on a control process in controlling the elevation of the movable table.

2. The brake mechanism includes: a brake motor that generates a braking force by shorting terminals of the motor via a resistor; 2. The bending machine according to claim 1, further comprising a timing belt stretched between a motor shaft of the brake motor and the drive shaft of the drive unit.

3. The brake mechanism includes: a fluid pressure cylinder connected to the movable table and generating a force for urging the movable table upward; 2. The bending machine according to claim 1, further comprising: an electromagnetic valve for controlling the supply and discharge of fluid to said fluid pressure cylinder.

4. 2. The bending machine according to claim 1, wherein the control device turns on the brake mechanism during a pressure deceleration period in which the movable table decelerates toward a lower end position while pressing the workpiece between a die mounted on the fixed table and a die mounted on the movable table.

5. 5. The bending machine according to claim 4, wherein the control device continues to keep the brake mechanism turned off even during the pressurizing and deceleration period when a predetermined prohibition condition is satisfied.

6. The drive unit includes: a reducer that reduces the rotation speed of a motor shaft of the drive motor and transmits the reduced rotation speed to the drive shaft; a clutch mechanism for switching the reduction ratio of the reducer, The control device includes: switching the clutch mechanism during the downward movement of the movable table from the upper end position to the lower end position, and switching the clutch mechanism during the upward movement of the movable table from the lower end position to the upper end position; 2. The bending machine according to claim 1, wherein the brake mechanism is turned on during a switching period in which the clutch mechanism is switched.

7. The control device includes:

2. The bending machine according to claim 1, wherein the brake mechanism is turned on during a sudden stop period when the movable table is suddenly stopped.

8. The control device includes:

2. The bending machine according to claim 1, wherein the brake mechanism is turned on during a table maintaining period during which the movable table is maintained at the upper end position.

9. The control device includes: After starting to apply pressure to the work between the die attached to the fixed table and the die attached to the movable table, the movable table is inverted upward before reaching the lower end position to release the pressure on the work, thereby unloading the work; 5. The bending machine according to claim 4, wherein the brake mechanism is turned on during a period in which the movable table is inverted.

10. A method for controlling a table of a bending machine, comprising the steps of: A drive unit is controlled to perform lift control for lifting and lowering a movable table disposed opposite to the fixed table in the vertical direction; switching on and off a brake mechanism according to a process of control in lifting and lowering control of the movable table; The drive unit includes: A drive motor; a plurality of gear elements engageable with one another by a tooth structure; a drive shaft connected to a conversion unit that converts rotational motion into linear motion to move the movable table in a vertical direction, and to which power from the drive motor is transmitted via the plurality of gear elements; The brake mechanism includes: A table control method for a bending machine that applies a force resisting a force that moves the movable table downward.

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