Bending machine and method for controlling table of bending machine

Abstract

A press brake (1) includes: an upper table (7) disposed to face a lower table (5) in an up-down direction; a drive unit (24) including a drive shaft (41) to which power from a driving motor (25) is transmitted via multiple gear elements; a ball screw mechanism (55) that converts rotational motion of the drive shaft (41) to linear motion along the up-down direction; a brake mechanism (70) that applies a force that resists a force of downward movement of the upper table (7); and a control device (100) that performs lifting / lowering control of the upper table (7) for bending a workpiece. The control device (100) switches on / off the brake mechanism (70) in accordance with a control process in the lifting / lowering control of the upper table (7).

Description

[TECHNICAL FIELD]

[0001] The present disclosure relates to a bending machine and a method for controlling a table of a bending machine.[BACKGROUND ART]

[0002] A press brake is configured to perform bending on a workpiece by moving a movable table, to which a tool such as a punch is mounted, in an up-down direction relative to a fixed table to which a tool such as a die is mounted. A table drive device that drives the movable table includes a drive unit that rotates a drive shaft by a driving motor, and a conversion unit that moves the movable table in the up-down direction by converting the rotational motion of the drive shaft to linear motion along the up-down direction. The drive unit includes multiple gear elements that can engage with each other through a tooth structure, and power from the driving motor is transmitted to the drive shaft via the multiple gear elements.

[0003] Patent Literature 1 discloses a technique for rotating a ball screw mechanism with a rotary drive source to move the movable table in the up-down direction.[Citation List][Patent Literature]

[0004] [Patent Literature 1] Japanese Patent Publication No. 5531878[SUMMARY OF INVENTION]

[0005] In a bending machine, it is necessary to perform lifting / lowering control to move the movable table upward and downward, but the weight of the movable table, which is a heavy object, affects various control issues. Therefore, to perform the lifting / lowering control of the movable table, it is necessary to fully consider the influence of the weight of the movable table.

[0006] A bending machine according to one or more embodiments includes a movable table disposed to face a fixed table in an up-down direction; a drive unit including a driving motor, multiple gear elements configured to be engageable with each other through a tooth structure, and a drive shaft to which power from the driving motor is transmitted via the multiple gear elements; a conversion unit configured to move the movable table in the up-down direction by converting rotational motion of the drive shaft to linear motion along the up-down direction; a brake mechanism configured to apply a force that resists a force of downward movement of the movable table; and a control device that controls the drive unit to perform lifting / lowering control of the movable table for bending a workpiece, wherein the control device switches on / off the brake mechanism in accordance with a control process in the lifting / lowering control of the movable table.

[0007] According to the bending machine related to one or more embodiments, by switching on / off the brake mechanism, it is possible to perform the lifting / lowering control of the movable table while considering the influence of the weight of the movable table.[BRIEF DESCRIPTION OF DRAWINGS]

[0008] [FIG. 1] FIG. 1 is a side view showing the main part of a table drive device of a press brake according to a present embodiment. [FIG. 2] FIG. 2 is a front view showing the overall configuration of the press brake according to the present embodiment. [FIG. 3] FIG. 3 is a cross-sectional view showing the main part of a reduction gear. [FIG. 4] FIG. 4 is a side view showing an enlarged main part of a clutch mechanism, illustrating the state of a high-speed mode. [FIG. 5] FIG. 5 is a side view showing the enlarged main part of the clutch mechanism, illustrating the state of a high-torque mode. [FIG. 6] FIG. 6 is an explanatory diagram showing a modification of a brake mechanism. [FIG. 7] FIG. 7 is a diagram explaining a series of processes in lifting / lowering control of an upper table. [FIG. 8] FIG. 8 is a diagram showing the transition of speed, torque, and pressure when the upper table descends in the high-torque mode, wherein the brake mechanism is not activated. [FIG. 9] FIG. 9 is a diagram showing the transition of speed, torque, and pressure when the upper table descends in the high-torque mode, wherein the brake mechanism is activated. [FIG. 10] FIG. 10 is a diagram showing the transition of speed, torque, and pressure when the upper table descends in the high-torque mode, wherein the brake mechanism is activated. [FIG. 11] FIG. 11 is a diagram showing the state of the clutch mechanism during mode switch from the high-speed mode to the high-torque mode. [FIG. 12] FIG. 12 is a diagram explaining emergency stop of the upper table. [FIG. 13] FIG. 13 is a diagram showing the transition of speed and torque when the upper table is brought to the emergency stop, wherein the brake mechanism is not activated. [FIG. 14] FIG. 14 is a diagram showing the transition of speed and torque when the upper table is brought to the emergency stop, wherein the brake mechanism is activated. [FIG. 15] FIG. 15 is a diagram showing the transition of speed and torque when the upper table descends from an upper end position, wherein the brake mechanism is not activated. [FIG. 16] FIG. 16 is a diagram showing the transition of speed and torque when the upper table descends from the upper end position, wherein the brake mechanism is activated. [FIG. 17] FIG. 17 is a diagram illustrating a series of processes in the lifting / lowering control of the upper table. [FIG. 18] FIG. 18 is a diagram showing the state of the clutch mechanism when the upper table is inverted. [DESCRIPTION OF EMBODIMENTS]

[0009] Hereinafter, with reference to the drawings, a bending machine according to a present embodiment will be described illustrating a press brake.

[0010] FIG. 1 is a side view showing the main part of a table drive device 20 of a press brake 1 according to the present embodiment. In this description, directions are defined using a left-right direction, front-rear direction, and up-down direction. The left-right direction and front-rear direction correspond to two directions that are orthogonal in a horizontal plane, while the up-down direction corresponds to a perpendicular direction. These directions are used merely for convenience in describing the press brake according to the present embodiment. In the drawings, rightward, leftward, upward, downward, forward, and rearward are indicated as RT, LT, UP, DN, FR, and RR, respectively.

[0011] The press brake 1 according to the present embodiment includes an upper table 7 disposed to face a lower table 5 in an up-down direction; a drive unit 24 including a driving motor 25, multiple gear elements configured to be engageable with each other through a tooth structure, and a drive shaft 41 to which power from the driving motor 25 is transmitted via the multiple gear elements; a ball screw mechanism 55 configured to move the upper table 7 in the up-down direction by converting rotational motion of the drive shaft 41 to linear motion along the up-down direction; a brake mechanism 70 configured to apply a force that resists a force of downward movement of the upper table 7; and a control device 100 configured to control the drive unit 24 to perform lifting / lowering control of the upper table 7 for bending a workpiece. The control device 100 switches on / off the brake mechanism 70 in accordance with a control process in the lifting / lowering control of the upper table 7.

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

[0013] As shown in FIG. 2, the press brake 1 performs bending on a sheet-like workpiece such as a sheet metal through the cooperation of 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, the lower table 5 that is a fixed table, the upper table 7 that is a movable table, left and right table drive devices 20, and the control device 100.

[0014] The left and right side plates 2 are arranged to be spaced apart in the left-right direction to face each other.

[0015] The lower table 5 extends in the left-right direction and is supported on the front lower part of the left and right side plates 2. On the upper side of the lower table 5, a lower tool holder 6 that can hold and detach the lower tool D is provided along the left-right direction.

[0016] The upper table 7 extends in the left-right direction and is supported on the upper front part of the left and right side plates 2 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. On the lower side of the upper table 7, an upper tool holder 8 that can hold and detach the upper tool P is provided along the left-right direction.

[0017] The left and right table drive devices 20 are fixed to upper portions 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 up-down direction. As shown in FIG. 1, the table drive device 20 is mainly composed of the drive unit 24, the ball screw mechanism 55, and the brake mechanism 70.

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

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

[0020] The reduction gear unit 30 includes multiple gear elements that can engage with each other through their tooth structure, and the drive shaft 41 to which power from the driving motor 25 is transmitted via the multiple gear elements. Due to the action of the multiple 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 driving motor shaft 26. Details of the reduction gear unit 30 will be described later. In the following description, if necessary, the drive shaft 41 of the reduction gear unit 30 is also referred to as the drive shaft 41 of the drive unit 24.

[0021] The ball screw mechanism 55 is a conversion unit that moves the upper table 7 in the up-down direction by converting the rotational motion of the drive shaft 41 of the drive unit 24 to linear motion. 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 a housing of the ball screw mechanism 55 via a bearing portion. The ball screw nut 56 is coupled to the drive shaft 41 of the drive unit 24 and rotates in accordance with the rotation of an output portion. The ball screw shaft 57 is screwed into the ball screw nut 56, and the ball screw nut 56 moves in the up-down direction by rotating in opposite directions.

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

[0023] At the lower end of the ball screw mechanism 55, specifically at the lower end of the ball screw shaft 57, a connection block 60 is coupled. At the lower end of the connection block 60, hanging bolts 61 that hang along the up-down direction are attached, and the hanging bolts 61 support a support shaft 62 that penetrates the upper table 7 in the front-rear direction. The ball screw shaft 57 is coupled to the upper table 7 via the connection block 60, which includes the hanging bolts 61 and the support shaft 62. In other words, the connection block 60 couples the ball screw mechanism 55 and the upper table 7, moving the upper table 7 in the up-down direction by the linear motion of the ball screw mechanism 55 in the up-down direction.

[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 a brake signal supplied from the control device 100 is on, that is, when it is instructed to activate the brake mechanism 70, the motor drive circuit short-circuits terminals of the motor via a resistor (between phases). 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, generating a brake force that stops the rotation of a brake motor shaft 72. In contrast, when the brake signal is off, that is, when it is instructed to turn off the brake mechanism 70, the motor drive circuit does not perform the above control. In this case, no brake force is generated on 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] Such a structure of the brake mechanism 70 is referred to as a dynamic brake. When moving the upper table 7 downward, the brake mechanism 70 is activated, and the brake force of the brake motor 71 acts as a resistor against the drive shaft 41 of the drive unit 24. In other words, the drive unit 24 is subjected to the force that resists the force of the downward movement of the upper table 7.

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

[0028] With reference to FIGS. 3 to 5, the reduction gear unit 30 will be described. FIG. 3 is a cross-sectional view showing the main part of the reduction gear unit 30. FIG. 4 is a side view showing an enlarged main part of a clutch mechanism 45 and illustrating the state of a high-speed mode. FIG. 5 is a side view showing an enlarged main part of the clutch mechanism 45 and illustrating the state of a high-torque mode. For the sake of convenience in description, the reduction gear unit 30 shown in FIG. 3 is depicted in an upside-down state compared to the state of the reduction gear unit 30 shown in FIG. 1. Furthermore, the clutch mechanism 45 shown in FIGS. 4 and 5 is depicted in accordance with the clutch mechanism 45 shown in FIG. 3 (the same applies below).

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

[0030] The reduction gear 31 includes a planetary gear mechanism of mechanical paradox type. Specifically, the reduction gear 31 includes a sun gear 32, multiple planetary gear units 33, a planetary carrier 34, a first internal gear 38, a second internal gear 40, and the drive shaft 41.

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

[0032] Multiple planetary gear units 33 are provided around the sun gear 32 and arranged at equal intervals in a circumferential direction. Each planetary gear unit 33 includes a first planetary gear 33a and a second planetary gear 33b. The first planetary gear 33a meshes with the sun gear 32 and is caused to rotate by 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 the present embodiment, the first planetary gear 33a and the second planetary gear 33b are integrated into a two-stage structure in the up-down direction, allowing the first planetary gear 33a and the second planetary gear 33b to rotate on the same shaft.

[0033] The planetary carrier 34 rotates about the driving motor shaft 26 via a bearing portion 35 fitted over the driving motor shaft 26. The planetary carrier 34 is provided with multiple unit shafts 36 along the circumferential direction. Bearing portions 37 are fitted over each unit shaft 36, and the planetary gear unit 33 is attached to the unit shaft via the bearing portions 37. The planetary carrier 34 rotatably supports each of multiple planetary gear units 33.

[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 peripheral surface of a housing of the reduction gear unit 30 via a bearing portion 39 and can rotate about the driving motor shaft 26.

[0035] The second internal gear 40 has a different number of teeth than the first internal gear 38 and is an internal gear that meshes with the second planetary gear 33b. The second internal gear 40 is provided on the inner peripheral surface of the housing of the reduction gear unit 30 via a bearing portion 42 and can rotate about the driving 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 coupled to the ball screw nut 56 of the ball screw mechanism 55 described above.

[0037] The clutch mechanism 45 includes a fixed clutch tooth 46, a first clutch tooth 47, and a second clutch tooth 48. The fixed clutch tooth 46, the first clutch tooth 47, and the second clutch tooth 48 are annular members, each provided with a tooth structure as described later. The first clutch tooth 47 and the second clutch tooth 48 are arranged opposite each other vertically, with their tooth structures facing each other. The fixed clutch tooth 46 is provided between the first clutch tooth 47 and the second clutch tooth 48.

[0038] As shown in FIGS. 4 and 5, the fixed clutch tooth 46 moves between the first clutch tooth 47 and the second clutch tooth 48. The fixed clutch tooth 46 is restricted from moving in directions other than the up-down direction. The fixed clutch tooth 46 is provided with multiple first engaging teeth 46a along the circumferential direction, as well as multiple second engaging teeth 46b along the circumferential direction. Each of the first engaging teeth 46a protrudes toward the first clutch tooth 47, and each of the second engaging teeth 46b protrudes toward the second clutch tooth 48.

[0039] The first clutch tooth 47 is coupled to the first internal gear 38 included in the reduction gear 31 and rotates integrally with this first internal gear 38 (see FIG. 3). The first clutch tooth 47 is provided with multiple third engaging teeth 47a along the circumferential direction. Each of the third engaging teeth 47a protrudes toward the fixed clutch tooth 46.

[0040] The second clutch tooth 48 is coupled to the planetary carrier 34 included in the reduction gear 31 and rotates integrally with this planetary carrier 34 (see FIG. 3). The second clutch tooth 48 is provided with multiple fourth engaging teeth 48a along the circumferential direction. Each of the fourth engaging teeth 48a protrudes toward the fixed clutch tooth 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 that presses the fixed clutch tooth 46 toward the first clutch tooth 47. That is, since the fixed clutch tooth 46 receives a pressing force from the pressing member, it normally moves toward the first clutch tooth 47. The solenoid 49, in turn, attracts the fixed clutch tooth 46 by an electromagnetic force, moving it to the second clutch tooth 48. In other words, when the solenoid 49 is activated to attract the fixed clutch tooth 46 by the electromagnetic force, the fixed clutch tooth moves toward the second clutch tooth 48 against the pressing force of the pressing member.

[0042] The fixed clutch tooth 46 has at least two operational modes as switchable operational modes. The two operational modes include the high-torque mode and the high-speed mode.

[0043] As shown in FIG. 4, the high-speed mode is a mode in which the fixed clutch tooth 46 meshes only with the second clutch tooth 48. When the fixed clutch tooth 46 meshes with the second clutch tooth 48, the second clutch tooth 48 is fixed, thereby restricting the rotation of the planetary carrier 34. In this case, the reduction gear 31 operates at a reduction ratio (first reduction ratio), which is smaller than a second reduction ratio.

[0044] As shown in FIG. 5, the high-torque mode is a mode in which the fixed clutch tooth 46 meshes only with the first clutch tooth 47. When the fixed clutch tooth 46 meshes with the first clutch tooth 47, the first clutch tooth 47 is fixed, thereby restricting the rotation of the first internal gear 38. In this case, the reduction gear 31 operates at a larger reduction ratio (second reduction ratio).

[0045] As described above, the press brake 1 is configured. In the above-described embodiment, an example of a dynamic brake is illustrated as the brake mechanism 70. However, the brake mechanism 70 is not limited to this example and may apply the force that resists the force of the downward movement of the upper table 7 to the drive unit 24.

[0046] FIG. 6 is an explanatory diagram showing a modification of the brake mechanism 70. The brake mechanism 70 according to the modification is mainly composed of an air cylinder 75 and an electromagnetic valve (not shown). The air cylinder 75 is a pneumatically operated actuator and is an example of a fluid pressure cylinder. Inside this air cylinder 75, there is provided a piston that can slide along the up-down direction. A rod 76 is connected to the piston. The rod 76 advances and retracts as the piston moves. The air cylinder 75 is fixed to an 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 electromagnetic valve controls air supply and discharge to and from the air cylinder 75 in response to the brake signal supplied from the control device 100 (supply and discharge control). When the brake signal supplied from the control device 100 is on, the electromagnetic valve performs first supply and discharge control. According to this first supply and discharge control, the air cylinder 75 generates a force Fc that lifts the upper table 7 upward via the rod 76. In contrast, when the brake signal is off, the electromagnetic valve performs second supply and discharge control. In this second supply and discharge control, the air cylinder 75 allows free movement of the rod 76 without generating the above force Fc.

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

[0049] Next, with reference also to FIG. 7, lifting / lowering control of the upper table 7 for bending the workpiece will be described. FIG. 7 is a diagram explaining a series of processes in the lifting / lowering control of the upper table. When processing the workpiece using the press brake 1, first, the workpiece is positioned on the lower tool D. Currently, the upper table 7 is supported at a predetermined upper end position P1.

[0050] The control device 100 causes the solenoid 49 to perform a suction operation. Consequently, the fixed clutch tooth 46 moves toward the second clutch tooth 48, so that the fixed clutch tooth 46 enters a high-speed mode in which the fixed clutch tooth meshes only with the second clutch tooth 48 (FIG. 4).

[0051] The control device 100 rotates the driving motor shaft 26 in a forward direction. In the high-speed mode, the planetary carrier 34 is fixed, and the first internal gear 38 is released. Since the planetary carrier 34 is fixed, the first planetary gear 33a, which meshes with the first internal gear 38, rotates in accordance with the rotation of the sun gear 32, which rotates integrally with the driving motor shaft 26, without revolving about the sun gear. In contrast, the rotation of the first planetary gear 33a also rotates the second planetary gear 33b integral with this first planetary gear, and the rotation of the second planetary gear 33b therefore causes the second internal gear 40 to rotate as well. Consequently, the drive shaft 41, which is coupled to the second internal gear 40, also rotates synchronously. Concurrently, the rotation of the driving motor shaft 26 is output to the drive shaft 41 by a simple planetary gear mechanism without being reduced by the planetary gear mechanism of mechanical paradox type. That is, the reduction ratio of the reduction gear 31 is the first reduction ratio. Therefore, the drive shaft 41 rotates in a high-speed, low-torque state, and the upper table 7 descends at high speed.

[0052] When the upper table 7 descends to a low-speed switching position P2, the control device 100 stops the rotation of the driving motor shaft 26. Thereafter, the control device 100 ends the suction operation of the solenoid 49. Consequently, the fixed clutch tooth 46 moves toward the first clutch tooth 47, and the fixed clutch tooth 46 therefore enters a high-torque mode in which the fixed clutch tooth meshes only with the first clutch tooth 47 (FIG. 5).

[0053] The control device 100 rotates the driving motor shaft 26 in reverse. In the high-torque mode, the first internal gear 38 is fixed, and the planetary carrier 34 is released. Therefore, the first planetary gear 33a, which meshes with the first internal gear 38, revolves about the sun gear 32, which rotates integrally with the driving motor shaft 26, while rotating on its axis. The rotation of the first planetary gear 33a also rotates the second planetary gear 33b that is integral with this first planetary gear, and the rotation of the second planetary gear 33b therefore causes the second internal gear 40, which has a different number of teeth than the first internal gear 38, to rotate as well. Consequently, the drive shaft 41, which is coupled to the second internal gear 40, also rotates synchronously. Currently, the rotation of the driving motor shaft 26 is significantly reduced by the planetary gear mechanism of mechanical paradox type and output to the drive shaft 41. That is, the reduction ratio of the reduction gear 31 is a second reduction ratio that is larger than the first reduction ratio. Therefore, the drive shaft 41 rotates in a low-speed, high-torque state, and the upper table 7 descends at 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 driving motor shaft 26 and holds a stopped state only for a certain period. The workpiece is pressurized between the upper tool P and the lower tool D and bent to a desired angle.

[0055] Next, the control device 100 rotates the driving motor shaft 26 in the forward direction. Currently, the rotation of the driving motor shaft 26 is significantly reduced by the planetary gear mechanism of mechanical paradox type and output to the drive shaft 41. Consequently, the upper table 7 rises at 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 driving motor shaft 26. Thereafter, the control device 100 causes the solenoid 49 to perform the suction operation. Consequently, the fixed clutch tooth 46 moves toward the second clutch tooth 48 and therefore enters the high-speed mode in which the fixed clutch tooth 46 meshes only with the second clutch tooth 48.

[0057] The control device 100 rotates the driving motor shaft 26 in reverse. Currently, the rotation of the driving motor shaft 26 is output to the drive shaft 41 by the simple planetary gear mechanism without being reduced by the planetary gear mechanism of mechanical paradox type. This causes the upper table 7 to rise at high speed. When the upper table 7 moves to the upper end position P1, the control device 100 stops the rotation of the driving motor shaft 26 and ends the suction operation of the solenoid 49.

[0058] As described above, in the press brake 1, the workpiece is bent through a series of processes in the lifting / lowering control of the upper table 7.

[0059] One of features of the press brake 1 according to the present embodiment is to switch on / off the brake mechanism 70 in accordance with the control process in the lifting / lowering control of the upper table 7. Specifically, the control device 100 activates the brake mechanism 70 during a pressurization deceleration period Ta, clutch switching period Tb, table maintenance period Tc, and emergency stop period Te (see FIG. 12). Hereinafter, the action of the brake mechanism 70 during each period will be described.<Pressurization Deceleration Period Ta>

[0060] With reference to FIGS. 8 to 10, the action of the brake mechanism 70 during the pressurization deceleration period Ta will be described. Here, FIGS. 8 to 10 show the transition of speed, torque, and pressure when the upper table 7 descends in the high-torque mode. In the drawings, FIG. 8 shows a case where the brake mechanism 70 is not activated, while FIGS. 9 and 10 show a case where the brake mechanism 70 is activated. The "speed" refers to the speed of the upper table 7, the "torque" refers to the torque of the driving motor 25, and the "pressure" refers to the pressure acting on the upper table 7 (the same applies below) .

[0061] The pressurization deceleration period Ta refers to a period during which the upper table 7 decelerates toward the lower end position P3 (see FIG. 7) while pressurizing the workpiece between the upper tool P and the lower tool 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) acting in a direction that pushes the upper table 7 downward acts on the driving motor 25. Then, as the table approaches the lower end position P3 and a deceleration torque acts, the upper table 7 decelerates. Concurrently, as shown in area A of FIG. 8, the deceleration torque may appear on a positive side. The phenomenon that the deceleration torque appears on the positive side becomes remarkable, for example, in (1) bending with a low load, such as the bending of thin plates, and (2) offset bending in which one drive shaft 41 of the left and right drive shafts 41 has a low load.

[0062] A reason for the deceleration torque appearing on the positive side is that a frictional force itself of the gear elements constituting the drive unit 24 is no longer sufficient to support the weight of the upper table 7, which is a heavy object, causing the driving motor 25 to generate a force that compensates for the weight of the upper table 7. Concurrently, the gear elements rotate by a gap between the engaged teeth, causing the upper table 7 to move downward. Consequently, even if the control device 100 stops the drive unit 24 at the lower end position P3, a problem arises in that the upper table 7 fails to align with the lower end position P3. This problem is likely to occur in various gear elements included in the drive unit 24, and the tooth structure of the clutch mechanism 45 will be described hereinafter 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) acting in a direction that pushes the upper table 7 downward acts on the driving motor 25, as shown in FIG. 5, the first clutch tooth 47, which meshes with the fixed clutch tooth 46, pushes the fixed clutch tooth 46 rightward in the drawing. When the torque of the driving motor 25, in turn, appears on the positive side, the force acting on the first clutch tooth 47 reverses, causing the first clutch tooth 47 to move by a gap Gp. This movement of the first clutch tooth 47 causes misalignment of the upper table 7.

[0064] Therefore, by activating the brake mechanism 70 during the pressurization deceleration period Ta, as shown in FIG. 9, the force that resists the force of the downward movement of the upper table 7 is applied to the drive unit 24 during deceleration. The deceleration torque of the driving motor 25 constitutes a component in the direction that pushes the upper table 7 downward. As shown in FIG. 5, a force directed rightward in the drawing continuously acts on the first clutch tooth 47, which can inhibit the first clutch tooth 47 from moving. This can suppress the misalignment of the upper table 7 and ensure accurate positioning of the upper table 7 at the lower end position P3.

[0065] As described above, the case where the torque appears on the positive side during deceleration is limited to certain processing conditions. Therefore, the control device 100 may activate the brake mechanism 70 during the pressurization deceleration period Ta only when certain execution conditions are met. Thus, if the control device 100 does not meet the execution conditions, that is, if it meets inhibiting conditions, it may continue to keep the brake mechanism 70 off even during the pressurization deceleration period Ta.

[0066] The control device 100 may determine whether the execution conditions are met based on the processing conditions. Furthermore, as shown in FIG. 9, a pressure threshold Th that is a judgment criterion is predetermined. The control device 100 may determine that the execution conditions are met when the pressure acting on the upper table 7 does not reach the pressure threshold Th, while it may determine that the inhibiting conditions are met when the pressure acting on the upper table 7 exceeds the pressure threshold Th.

[0067] Furthermore, the period during which the brake mechanism 70 is activated may include at least the pressurization deceleration period Ta. Therefore, as shown in FIG. 10, the brake mechanism 70 may be activated a certain time prior to the deceleration timing of the upper table 7. Alternatively, the brake mechanism 70 may be kept on for a certain time after the upper table 7 is stopped.<Clutch Switching Period Tb>

[0068] The action of the brake mechanism 70 during the clutch switching period Tb will be described. The clutch switching period Tb is the period during which the fixed clutch tooth 46 is 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 lowering the upper table 7 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 raising the upper table 7 from the lower end position P3 to the upper end position P1 (specifically at the high-speed switching position P4).

[0069] FIG. 11 shows the state of the clutch mechanism 45 during mode switch from the high-speed mode to the high-torque mode. A "state A1" in FIG. 11 shows the state of the clutch mechanism 45 before the mode switch. When transitioning the fixed clutch tooth 46 to the high-torque mode, depending on a positional relation between the first clutch tooth 47 and the fixed clutch tooth 46, the tip of the third engaging tooth 47a at the first clutch tooth 47 may interfere with the tip of the first engaging tooth 46a at the fixed clutch tooth 46. A situation may arise where the fixed clutch tooth 46 cannot transition to the high-torque mode.

[0070] Therefore, prior to the switch from the high-speed mode to the high-torque mode, the control device 100 performs control to rotate the driving motor shaft 26, rotating the first clutch tooth 47 by a predetermined rotation angle in a direction R1. Consequently, a phase between the first clutch tooth 47 and the fixed clutch tooth 46 shifts, allowing the tip of the first engaging tooth 46a at the fixed clutch tooth 46 to correspond to a gap between third engaging teeth 47a at the first clutch tooth 47 (state B1). As a result, the fixed clutch tooth 46 can transition to the high-torque mode.

[0071] During control for rotating the first clutch tooth 47, however, a frictional force of parts constituting the drive unit 24 is no longer sufficient to support the weight of the upper table 7, which is a heavy object, causing the first clutch tooth 47 to rotate. In this case, the tip of the third engaging tooth 47a at the first clutch tooth 47 may interfere with the tip of the first engaging tooth 46a at the fixed clutch tooth 46 (state C11). A success rate of mode switching by the clutch mechanism 45 decreases.

[0072] As shown in FIG. 9, however, the brake mechanism 70 is activated during the clutch switching period Tb. Thus, the force that resists the force of the downward movement of the upper table 7 is applied to the drive unit 24. Since the brake mechanism 70 bears the weight of the upper table 7, it can suppress the rotation of the first clutch tooth 47 (state C12). Therefore, the success rate of the mode switching by the clutch mechanism 45 can be increased.

[0073] Note that FIG. 11 shows the state of the clutch mechanism 45 during the mode switch from the high-speed mode to the high-torque mode, and the same applies during the mode switch from the high-torque mode to the high-speed mode. Furthermore, the period during which the brake mechanism 70 is activated may include at least the clutch switching period Tb. Therefore, the brake mechanism 70 may be activated either a certain time prior to the clutch switching period Tb or a certain time after the clutch switching period Tb.<Emergency Stop Period Te>

[0074] FIG. 12 is a diagram explaining the emergency stop of the upper table 7. In the lifting / lowering control of the upper table 7, the control device 100 triggers the emergency stop of the upper table 7 based on predetermined conditions including alarm generation. Concurrently, the control device 100 may activate the brake mechanism 70 during the emergency stop period Te for the emergency stop of the upper table 7.

[0075] FIGS. 13 and 14 show the transition of speed and torque when the upper table 7 is brought to the emergency stop. In the drawings, FIG. 13 is a diagram where the brake mechanism 70 is not activated, and FIG. 14 is a diagram where the brake mechanism 70 is activated.

[0076] When the brake mechanism 70 is not used, as shown in FIG. 13, the control device 100 can rapidly decelerate the upper table 7 by controlling the rotation of the driving motor 25. However, when the brake mechanism 70 is activated, it can support the weight of the upper table 7 with the force generated by the brake mechanism 70. Therefore, the brake force generated by the driving motor 25 is assisted by the force of the brake mechanism 70. Thus, a large brake force is applied to the upper table 7, allowing the upper table 7 to be stopped quickly.

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

[0078] With reference to FIGS. 15 and 16, the action of the brake mechanism 70 during the table maintenance period Tc will be described. Here, FIGS. 15 and 16 show the transition of speed and torque when the upper table 7 descends from the upper end position P1. In the drawings, FIG. 15 is a diagram where the brake mechanism 70 is not activated, and FIG. 16 is a diagram where the brake mechanism 70 is activated.

[0079] The table maintenance period Tc is a period during which the upper table 7 is held at the upper end position P1 (see FIG. 7). When the brake mechanism 70 is not used, in order to hold the upper table 7 at the upper end position P1 (see FIG. 7), as shown in FIG. 15, it is necessary to generate a static torque for stopping the upper table 7 by operating the driving motor 25. However, during the table maintenance period Tc during which the brake mechanism 70 is activated, the brake mechanism 70 generates force, so that the weight of the upper table 7 can be supported. Consequently, as shown in FIG. 16, it is possible to expect energy savings because it is not necessary to operate the high output driving motor 25.(Modification of Press Brake 1)

[0080] FIG. 17 is a diagram explaining a series of processes in the lifting / lowering control of the upper table 7. There are various models of press brake 1, on some of which a sensor unit that automatically measures the bending angle of the workpiece is mounted. In press brakes on which such sensor units are mounted, after starting to pressurize the workpiece, the upper table 7 is inverted upward to release the pressure on the workpiece before reaching the lower end position P3 (unloading). Then, while the workpiece is in a state of spring back, the sensor unit measures the bending angle of the workpiece. The measured bending angle of the workpiece is processed by the control device 100, and the lower end position P3 is corrected, as necessary. Subsequently, the workpiece is pressurized in accordance with the corrected lower end position P3.

[0081] When such an unloading process is included, the control device 100 may activate the brake mechanism 70 during an inversion period Tf for inverting the upper table 7.

[0082] FIG. 18 shows 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 lowered, a force in a direction R2 acts on the first clutch tooth 47 as the driving motor 25 rotates.

[0083] In addition, to perform depressurization, it is necessary to move the upper table 7 upward, so the control device 100 reverses a rotating direction after stopping the rotation of the driving motor shaft 26. Concurrently, a force directed in direction R1 acts on the first clutch tooth 47 from the driving motor 25, and a gap between the first clutch tooth 47 and the fixed clutch tooth 46 is closed (state B21). Closing the gap between the first clutch tooth 47 and the fixed clutch tooth 46 initiates the movement of the upper table 7.

[0084] In addition, if the brake mechanism 70 is activated during the inversion of the upper table 7, the force that resists the force of the downward movement of the upper table 7 is applied to the drive unit 24. Consequently, the first clutch tooth 47 moves due to the force generated by the brake mechanism 70, thereby closing the gap between the first clutch tooth 47 and the fixed clutch tooth 46. That is, the gap between the first clutch tooth 47 and the fixed clutch tooth 46 can be closed without receiving any force from the driving motor 25 (state B22). This allows for improved responsiveness during the inverting operation of the upper table 7.

[0085] In addition, when activating the brake mechanism in conjunction with the inversion of the movable table, the above effects can be appropriately obtained using the brake mechanism 70 including a fluid pressure cylinder as shown in FIG. 7. Furthermore, the brake mechanism 70 may be activated a certain period prior to the inversion period Tf of the upper table 7.

[0086] According to the present embodiment, the control of the upper table 7 can be performed while fully considering the action of the weight of the upper table 7. Thus, as described above, it is possible to obtain specific effects in each process. Moreover, the table control method for the press brake 1 (bending machine) described above also functions as part of the present embodiment.

[0087] As above, the present embodiment has been described, but it should not be understood that the discussions and drawings that form part of this embodiment limit the embodiment. This embodiment will reveal various alternative forms of implementation, examples, and operational techniques to those skilled in the art.

[0088] The disclosure of this application relates to the subject matter described in Japanese Patent Application No. 2023-113196, filed with the Japan Patent Office on July 10, 2023, and all its disclosures are incorporated herein by reference.

Claims

1. A bending machine comprising: a movable table disposed to face a fixed table in an up-down direction; a drive unit including a driving motor, multiple gear elements configured to be engageable with each other through a tooth structure, and a drive shaft to which power from the driving motor is transmitted via the multiple gear elements; a conversion unit configured to move the movable table in the up-down direction by converting rotational motion of the drive shaft to linear motion along the up-down direction; a brake mechanism configured to apply a force that resists a force of downward movement of the movable table; and a control device that controls the drive unit to perform lifting / lowering control of the movable table for bending a workpiece, wherein the control device switches on / off the brake mechanism in accordance with a control process in the lifting / lowering control of the movable table.

2. The bending machine according to claim 1, wherein the brake mechanism includes: a brake motor configured to generate a brake force by short-circuiting terminals of the motor via a resistance, and a timing belt stretched between a motor shaft of the brake motor and the drive shaft of the drive unit.

3. The bending machine according to claim 1, wherein the brake mechanism includes: a fluid pressure cylinder configured to be coupled to the movable table and generate a force that urges the movable table upward, and an electromagnetic valve configured to control supply and discharge of fluid to and from the fluid pressure cylinder.

4. The bending machine according to claim 1, wherein the control device activates the brake mechanism during a pressurization deceleration period during which the movable table decelerates toward a lower end position, while pressurizing the workpiece between a tool mounted to the fixed table and a tool mounted to the movable table.

5. The bending machine according to claim 4, wherein the control device continues to keep the brake mechanism off even during the pressurization deceleration period, when predetermined inhibiting conditions are met.

6. The bending machine according to claim 1, wherein the drive unit includes: a reduction gear configured to reduce rotation of a motor shaft of the driving motor and transmit the reduced rotation to the drive shaft, and a clutch mechanism configured to switch a reduction ratio in the reduction gear, and the control device switches the clutch mechanism while lowering the movable table from an upper end position to a lower end position, switches the clutch mechanism while raising the movable table from the lower end position to the upper end position, and activates the brake mechanism during a switching period for switching the clutch mechanism.

7. The bending machine according to claim 1, wherein the control device activates the brake mechanism during an emergency stop period for bringing the movable table to an emergency stop.

8. The bending machine according to claim 1, wherein the control device activates the brake mechanism during a table maintenance period for holding the movable table at an upper end position.

9. The bending machine according to claim 4, wherein after starting pressurization of the workpiece between a tool mounted to the fixed table and a tool mounted to the movable table, the control device is configured to: perform unloading by inverting the movable table upward to release the pressurization on the workpiece before the movable table reaches the lower end position, and activate the brake mechanism during an inversion period of the movable table.

10. A table control method for a bending machine, comprising: controlling a drive unit to perform lifting / lowering control for lifting and lowering a movable table disposed to face a fixed table in an up-down direction; and switching on / off a brake mechanism in accordance with a control process in the lifting / lowering control of the movable table, wherein the drive unit includes: a driving motor; multiple gear elements configured to be engageable with each other through a tooth structure; and a drive shaft coupled to a conversion unit configured to move the movable table in the up-down direction by converting rotational motion to linear motion, the drive shaft to which power from the driving motor is transmitted via the multiple gear elements, and the brake mechanism applies a force that resists a force of downward movement of the movable table.

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