JP7584598B1 - Bending machine - Google Patents

Abstract

The present invention aims to stabilize the positioning of a movable table and improve machining accuracy.
[Solution] The control device 100 has a high-speed mode and a high-torque mode as switchable operating modes. In the high-speed mode, the upper table 7 is moved by driving a high-speed motor unit 26 that rotates at a high speed and outputs low torque with torque cut off by a clutch 29. In the high-torque mode, the upper table 7 is moved by driving a pressure motor unit 27 that rotates at a low speed and outputs high torque with torque transmitted by the clutch 29. When moving the upper table 7 downward in the high-torque mode, the control device 100 performs reversal control to drive the high-speed motor unit 26 in the opposite direction to the rotation direction when moving the upper table 7 downward with torque transmitted by the clutch 29.
[Selected figure] Figure 2

Description

The present invention relates to a bending machine.

A press brake performs bending processing on a workpiece by moving a movable table, on which dies such as punches are attached, in the vertical direction relative to a fixed table on which dies and other dies are attached. The table drive device that drives the movable table includes a rotational power unit and a conversion mechanism that converts the rotational motion caused by the torque of the rotational power unit into linear motion along the vertical direction, thereby moving the movable table in the vertical direction.

Patent Document 1 discloses a variable torque motor that includes a motor body, a reducer that uses a paradox planetary gear mechanism, and a clutch that is provided between the motor body and the reducer. This variable torque motor can switch between a mode that produces high torque at low rotation speeds and a mode that produces low torque at high rotation speeds by selectively fixing the carrier and second internal gear of the paradox planetary gear mechanism with the clutch action portion of the clutch.

JP 2021-136855 A

In a structure in which torque is transmitted by mechanical elements such as gears, as in Patent Document 1, gaps are intentionally provided between the mechanical elements to ensure smooth operation of the mechanical elements. This gap causes slight movement of the mechanical elements, which can lead to unstable positioning of the movable table and reduced machining accuracy.

A bending machine according to one embodiment of the present invention comprises a movable table arranged vertically opposite a fixed table, a rotational power unit which generates torque, a conversion mechanism which converts rotational motion due to the torque of the rotational power unit into linear motion along the vertical direction to move the movable table vertically, and a control device which controls the rotational power unit to bend a workpiece using dies attached to the fixed table and the movable table, respectively. The rotational power unit comprises a high-speed motor unit, a pressure motor unit which rotates at a slower speed than the high-speed motor unit and outputs high torque, a power transmission mechanism which transmits the torque of the high-speed motor unit to the conversion mechanism and transmits the torque of the pressure motor unit to the conversion mechanism, and a clutch which can interrupt the transmission of torque from the pressure motor unit to the power transmission mechanism. The control device has switchable operating modes: a high-speed mode in which the movable table is moved by driving the high-speed motor unit with torque interrupted by the clutch, and a high-torque mode in which the movable table is moved by driving the pressure motor unit with torque transmitted by the clutch. When the movable table is moved downward in the high-torque mode, reversal control is performed to drive the high-speed motor unit in the opposite direction to the rotation direction when moving the movable table downward with torque transmitted by the clutch.

According to one aspect of the bending machine of the present invention, when the movable table is moved downward in high torque mode, the movement of the mechanical elements that transmit the torque can be suppressed, so that the movable table can be stably positioned.

According to one aspect of the present invention, the positioning of the movable table is stable, which improves machining accuracy.

FIG. 1 is a front view showing a schematic structure of a press brake according to a first embodiment. FIG. 2 is a side view illustrating a schematic diagram of the table drive device of the press brake according to the first embodiment. FIG. 3 is a conceptual diagram showing gear elements (machine elements) that transmit torque. FIG. 4 is a conceptual diagram showing gear elements (machine elements) that transmit torque. FIG. 5 is a side view illustrating a table driving device of a press brake according to the second embodiment.

Below, we will explain the bending machine according to this embodiment by using a press brake as an example, with reference to the drawings.

First Embodiment
FIG. 1 is a front view showing a schematic structure of a press brake 1 according to the first embodiment. FIG. 2 is a side view showing a schematic table drive device 20 of the press brake 1 according to the first 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 that are orthogonal to the horizontal direction, and the up-down direction corresponds to the vertical direction. In FIG. 1, the front-rear direction corresponds to the direction perpendicular to the paper surface, and in FIG. 2, the left-right direction corresponds to the direction perpendicular to the paper surface. These directions are merely used for convenience in order to explain the press brake 1 according to this embodiment.

The press brake 1 according to this embodiment includes an upper table 7 arranged vertically opposite to the lower table 5, a rotational power unit 25 that generates torque, a ball screw mechanism 55 that converts the rotational motion caused by the torque of the rotational power unit 25 into linear motion along the vertical direction to move the upper table 7 vertically, and a control device 100 that controls the rotational power unit 25 to bend the workpiece using dies P and D attached to the lower table 5 and the upper table 7, respectively. The rotational power unit 25 includes a high-speed motor unit 26, a pressure motor unit 27 that outputs high torque at a slower rotation speed than the high-speed motor unit 26, a power transmission mechanism 35 that transmits the torque of the high-speed motor unit 26 to the ball screw mechanism 55 and transmits the torque of the pressure motor unit 27 to the ball screw mechanism 55, and a clutch 29 that can interrupt the transmission of torque from the pressure motor unit 27 to the power transmission mechanism 35. The control device 100 has switchable operating modes: a high-speed mode in which the upper table 7 is moved by driving the high-speed motor unit 26 with torque cut off by the clutch 29, and a high-torque mode in which the upper table 7 is moved by driving the pressure motor unit 27 with torque transmitted by the clutch 29. When moving the upper table 7 downward in the high-torque mode, the control device 100 performs reversal control to drive the high-speed motor unit 26 in the opposite direction to the rotation direction when moving the upper table 7 downward with torque transmitted by the clutch 29.

The details of the press brake 1 are described below with reference to Figures 1 and 2.

The press brake 1 is a bending machine that performs bending processing on plate-shaped workpieces such as 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 is equipped with 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 drive devices 20, and a control device 100.

The left and right side plates 2 are arranged opposite each other and spaced apart in the left-right direction.

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 that detachably holds a lower die D is provided above the lower table 5 along the left-right direction.

The upper table 7 extends in the left-right direction and is supported on the upper front sides 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.

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. 2, the table drive device 20 is mainly composed of a rotational power unit 25 and a ball screw mechanism 55.

The rotational power unit 25 generates torque to operate the ball screw mechanism 55. The rotational power unit 25 is composed of a high-speed motor unit 26, a pressure motor unit 27, a clutch 29, and a power transmission mechanism 35.

The high-speed motor unit 26 is composed of a first drive motor 26a. The first drive motor 26a is a device that generates torque using electrical energy, such as a servo motor.

The pressure motor unit 27 is composed of a second drive motor 27a and a reduction gear 27b. The first drive motor 26a is a device that generates torque using electrical energy, such as a servo motor. The reduction gear 27b reduces the rotational power (torque) of the second drive motor 27a and outputs it. The pressure motor unit 27 outputs high torque at a slower rotation speed than the high-speed motor unit 26.

The clutch 29 transmits torque from the pressure motor unit 27 to the power transmission mechanism 35, or blocks the transmission of this torque. The clutch 29 is a tooth clutch that transmits torque by meshing teeth, but is not limited to this.

The clutch 29 is disposed between the reducer 27b of the pressure motor unit 27 and the drive pulley 37 of the power transmission mechanism 35, which will be described later. For example, when the teeth of the clutch 29 are engaged (transmission state), the clutch 29 transmits torque from the output shaft of the reducer 27b to the drive pulley 37. On the other hand, when the teeth of the clutch 29 are not engaged (released state), the clutch 29 blocks the transmission of torque from the output shaft of the reducer 27b to the drive pulley 37.

The clutch 29 is not limited to the above-mentioned configuration as long as it is provided in the power transmission path from the second drive motor 27a to the drive pulley 37. For example, the clutch 29 may be interposed between the second drive motor 27a and the reducer 27b.

The power transmission mechanism 35 transmits the torque of the rotational power unit 25 to the ball screw mechanism 55. That is, the power transmission mechanism 35 transmits the torque of the high-speed motor unit 26 to the ball screw mechanism 55, and also transmits the torque of the pressure motor unit 27 to the ball screw mechanism 55. The power transmission mechanism 35 is composed of a timing belt 36, a driving pulley 37, and a driven pulley 38.

The timing belt 36 is stretched between a drive pulley 37 and a driven pulley 38. The drive pulley 37 is connected to the output shaft of the high-speed motor unit 26, i.e., the drive shaft of the first drive motor 26a. The drive pulley 37 is also connected to the output shaft of the pressure motor unit 27, i.e., the output shaft of the reducer 27b, via a clutch 29. The driven pulley 38 is connected to a ball screw nut 56 of a ball screw mechanism 55, which will be described later.

In this embodiment, the high-speed motor unit 26 is arranged coaxially on the opposite side of the pressure motor unit 27 with the drive pulley 37 in between. Specifically, the high-speed motor unit 26 is arranged above the drive pulley 37, and the pressure motor unit 27 is arranged below the drive pulley 37. The first drive motor 26a, the second drive motor 27a, the reducer 27b, and the clutch 29 are each arranged coaxially.

The ball screw mechanism 55 is a conversion mechanism that converts the rotational motion caused by the torque of the rotational power unit 25 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 driven pulley 38 of the power transmission mechanism 35, and rotates in response to the rotation of the driven pulley 38. 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.

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 that hangs 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 that passes through 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, which includes the hanging bolt 61 and the support shaft 62.

A control device 100, such as an NC (Numerical Control) device that controls the operation of the press brake 1, is supported on the side plate 2 via a connecting arm.

The control device 100 is composed of a computer having a hardware processor such as a CPU (Central Processing Unit), a memory, and various interfaces. The memory and various interfaces are connected to the hardware processor via a bus. The various functions of the control device 100 are realized by having the hardware processor execute programs stored in the memory.

The control device 100 controls the rotary power unit. The control device 100 has two switchable operating modes: a high-speed mode and a high-torque mode. The high-speed mode is an operating mode in which the upper table 7 is moved by driving the high-speed motor unit 26 with torque interrupted by the clutch 29. The high-torque mode is an operating mode in which the upper table 7 is moved by driving the pressure motor unit 27 with torque transmitted by the clutch 29.

The control of the press brake 1 for bending a workpiece will be described below. When processing a workpiece using the press brake 1, the workpiece is first positioned on the lower die D. At this time, the upper table 7 is held at a predetermined upper end position. The clutch 29 is set to a released state. In other words, the transmission of torque from the pressure motor unit 27 to the power transmission mechanism 35 is interrupted.

First, the control device 100 drives the high-speed motor unit 26 in the rotation direction for moving the upper table 7 downward. This rotates the output shaft of the high-speed motor unit 26 (the drive shaft of the first drive motor 26a), which outputs low torque at high speed, and the upper table 7 descends at high speed (high-speed mode).

When the upper table 7 moves to a predetermined low-speed switching position (approach position), the control device 100 stops the high-speed motor unit 26. The control device 100 switches the clutch 29 to a transmission state. This allows torque to be transmitted from the pressure motor unit 27 to the power transmission mechanism 35. The control device 100 drives the pressure motor unit 27 in the rotation direction when moving the upper table 7 downward. This causes the output shaft of the pressure motor unit 27 (output shaft of the reducer 27b), which outputs high torque at low rotation speed, to rotate, and the upper table 7 descends at a low speed (high torque mode).

As one of the features of this embodiment, when the upper table 7 is moved downward in high torque mode, the control device 100 performs reversal control to drive the high-speed motor unit in the opposite direction to the rotation direction when the upper table 7 is moved downward. Details of the reversal control will be described later.

The control device 100 controls the pressure motor unit 27 to stop the upper table 7 at a predetermined lower end position (stroke position). As the upper table 7 reaches the lower end position, the workpiece is pressed between the upper die P and the lower die D and bent to the desired angle.

Next, the control device 100 drives the pressure motor unit 27 in the rotation direction for moving the upper table 7 upward. This causes the upper table 7 to rise at a low speed.

When the upper table 7 rises to a predetermined high-speed switching position, the control device 100 stops the pressure motor unit 27. The control device 100 switches the clutch 29 to a released state. This blocks the torque transmission from the pressure motor unit 27 to the power transmission mechanism 35.

The control device 100 drives the high-speed motor unit 26 in the rotation direction for moving the upper table 7 upward. This rotates the output shaft of the high-speed motor unit 26 (the drive shaft of the first drive motor 26a), and the upper table 7 rises at high speed. When the upper table 7 moves to the upper end position, the control device 100 stops the high-speed motor unit.

In the press brake 1, bending of the workpiece is performed through a series of steps like this. The operation of the reversal control is explained below.

When the upper table 7 is descending in high torque mode, the upper table 7 decelerates in order to stop at the bottom end position while the workpiece is being pressurized between the upper die P and the lower die D. When the upper table 7 starts moving from the low speed switching position and descends at a constant speed, a torque (negative torque) acts on the second drive motor 27a in a direction that pushes the upper table 7 downward. As it approaches the bottom end position, the deceleration torque of the second drive motor 27a acts to decelerate the upper table 7, and finally the upper table 7 is positioned at the bottom end position.

Figures 3 and 4 are conceptual diagrams showing gear elements (machine elements) T1 and T2 that transmit torque in the reducer 27b and clutch 29. The figures show the main parts of the gear elements T1 and T2 that rotate about an axis, and the direction of rotation of the gear elements T1 and T2 corresponds to the left-right direction on the page. Of the gear elements T1 and T2, gear element T1 is the gear element connected to the drive pulley 37 side, and gear element T2 is the gear element connected to the second drive motor 27a side.

A gap is intentionally provided between the gear elements T1 and T2 to allow the machine to move smoothly. In Figures 3 and 4, the gap is depicted as a space in the left-right direction between the teeth. When the frictional force of the gear elements T1 and T2 alone is no longer enough to support the upper table 7, which is a heavy object, the gear element T1 rotates by a small amount ΔG, causing the upper table 7 to move downward. For this reason, even if the control device 100 stops the pressure motor unit 27 in accordance with the lower end position, a problem occurs in which the upper table 7 shifts from the lower end position.

In high-load bending, such as bending thick plates, a high bending reaction force acts on the upper table 7 from the workpiece, and the bending reaction force acts in a direction that supports the weight of the upper table 7. Therefore, the phenomenon in which the positioning of the upper table 7 becomes unstable occurs significantly in low-load bending, such as bending thin plates. In addition to this, such a phenomenon can also occur in offset bending, where one of the left and right table drive devices 20 is under a low load.

In consideration of such phenomena, when the control device 100 moves the upper table 7 downward in high torque mode, it performs reverse control with torque transmitted by the clutch 29. By performing reverse control, the high-speed motor unit 26 is driven in the opposite direction to the pressure motor unit 27, so that rotation R1 in the opposite direction to rotation R2 of the gear element T2 acts on the gear element T1. This maintains a state in which the gear element T2 continues to press the gear element T1 until the upper table 7 reaches the lower end position. Since minute movements of the gear element T1 are suppressed, it is possible to suppress the upper table 7 from moving downward. Therefore, the upper table 7 is accurately positioned with respect to the lower end position. Since the positioning of the upper table 7 is stable, it is possible to improve the machining accuracy.

The slight movement of the gear element T1 occurs during the deceleration period in which the upper table 7 is decelerated. Therefore, the period in which the reversal control is performed needs to include at least the deceleration period. For example, the control device 100 may start the reversal control in accordance with the timing at which the upper table 7 starts to decelerate, or may start the reversal control a certain time before the timing at which the deceleration starts.

As described above, the phenomenon in which the positioning of the upper table 7 becomes unstable occurs particularly in low-load bending, such as bending thin plates. Therefore, the control device 100 may perform inversion control in cases such as low-load bending, in which the load for bending the workpiece is lower than a predetermined threshold value. This allows appropriate control to be performed in situations in which the positioning of the upper table 7 becomes unstable.

In the case of high-load bending where the load for bending the workpiece is equal to or greater than a threshold, the above-mentioned reversal control is not necessary. On the other hand, the control device 100 may perform assist control to drive the high-speed motor unit 26 in the rotation direction when moving the upper table 7 downward. This makes it possible to increase the pressure applied by the upper table 7, so that bending can be performed on workpieces that require a high load.

In this way, with the press brake 1 according to this embodiment, the upper table 7 can be accurately positioned relative to the lower end position by performing inversion control. Since the positioning of the upper table 7 is stable, it is possible to improve the machining accuracy.

In this embodiment, the high-speed motor unit 26 includes a first drive motor 26a. The pressure motor unit 27 includes a second drive motor 27a and a reducer 27b that reduces the torque of the second drive motor 27a and outputs it. With this configuration, since the pressure motor unit 27 includes the reducer 27b, the pressure motor unit 27 can obtain high torque at a low rotation speed.

In this embodiment, the high-speed motor unit 26 is composed of only the first drive motor 26a. However, the high-speed motor unit 26 may include a reducer, similar to the pressure motor unit 27, so long as it outputs lower torque at a higher rotation speed than the pressure motor unit 27.

In this embodiment, the power transmission mechanism 35 includes a drive pulley 37 to which the high-speed motor unit 26 and the pressure motor unit 27 are respectively connected, a driven pulley 38 connected to the ball screw mechanism 55, and a timing belt 36 stretched between the drive pulley 37 and the driven pulley 38. In this case, the high-speed motor unit 26 is coaxially arranged on the opposite side of the pressure motor unit 27 with the drive pulley 37 in between.

This configuration allows the high-speed motor unit 26 and the pressure motor unit 27 to share mechanical components such as the timing belt 36 and the drive pulley 37. This makes it possible to reduce the inertia of the mechanical elements while suppressing increases in costs. In addition, because the high-speed motor unit 26 and the pressure motor unit 27 are arranged side-by-side in the vertical direction, spatial expansion in the left-right and front-rear directions can be suppressed. This makes it possible to achieve space saving for the machine.

Second Embodiment
The press brake 1 according to the second embodiment will be described below. One of the features of the press brake 1 according to the second embodiment is the configuration of the rotation power unit 25 and the power transmission mechanism 35. Below, differences from the first embodiment will be mainly described with reference to Fig. 5. Fig. 5 is a side view that shows a schematic diagram of the table drive device 20 of the press brake 1 according to the second embodiment.

In this embodiment, the high-speed motor unit 26 and the pressure motor unit 27 are arranged on separate shafts. The high-speed motor unit 26 is arranged with its output shaft (the drive shaft of the first drive motor 26a) facing upward, and the pressure motor unit 27 is also arranged with its output shaft (the output shaft of the reducer 27b) facing upward.

The power transmission mechanism 35 is composed of a first timing belt 36a, a second timing belt 36b, a first driving pulley 37a, a second driving pulley 37b, and a driven pulley 38.

The first timing belt 36a is stretched between the first driving pulley 37a and the driven pulley 38. The second timing belt 36b is stretched between the second driving pulley 37b and the driven pulley 38.

The output shaft of the high-speed motor unit 26, i.e., the drive shaft of the first drive motor 26a, is connected to the first drive pulley 37a. The output shaft of the pressure motor unit 27, i.e., the output shaft of the reducer 27b, is connected to the second drive pulley 37b via the clutch 29. The ball screw nut 56 of the ball screw mechanism 55 is connected to the driven pulley 38.

With this configuration, the reduction ratio can be set according to the ratio of the pulley diameters of the first drive pulley 37a and the driven pulley 38. This allows for flexible torque and speed settings.

In addition, since the high-speed motor unit 26 and the pressure motor unit 27 are not aligned vertically, the height of the machine can be reduced.

In the first and second embodiments, rotational motion is input to the ball screw nut 56 of the ball screw mechanism 55, and this rotational motion is converted into linear motion by the ball screw shaft 57. However, rotational motion may be input to the ball screw shaft 57, and this rotational motion may be converted into linear motion by the ball screw nut 56.

Although the present embodiment has been described, the description and drawings forming a part of this embodiment should not be understood as limiting this embodiment. Various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art from this embodiment.

1 Press brake 2 Side plate 5 Lower table (fixed table)
7 Upper table (movable table)
20 Table drive device 25 Rotational power unit 26 High-speed motor unit 26a First drive motor 27 Pressure motor unit 27a Second drive motor 27b Speed reducer 29 Clutch 35 Power transmission mechanism 36 Timing belt 36a First timing belt 36b Second timing belt 37 Drive pulley 37a First drive pulley 37b Second drive pulley 38 Driven pulley 55 Ball screw mechanism (conversion mechanism)
56 Ball screw nut 57 Ball screw shaft 100 Control device

Claims (6)

a movable table disposed opposite to the fixed table in the up-down direction;
A rotational power unit that generates torque;
a conversion mechanism that converts a rotational motion caused by the torque of the rotation power unit into a linear motion along a vertical direction, thereby moving the movable table in a vertical direction;
a control device that controls the rotary power unit to perform bending processing on a workpiece using dies attached to the fixed table and the movable table,
The rotary power unit includes:
A high-speed motor unit;
a pressure motor unit that outputs high torque at a slower rotation speed than the high-speed motor unit;
a power transmission mechanism that transmits the torque of the high-speed motor unit to the conversion mechanism and transmits the torque of the pressurizing motor unit to the conversion mechanism;
a clutch capable of interrupting transmission of torque from the pressure applying motor unit to the power transmission mechanism,
The control device includes:
Switchable operation modes:
a high-speed mode in which the high-speed motor unit is driven with torque interrupted by the clutch to move the movable table;
a high torque mode in which the pressurizing motor unit is driven in a state in which torque is transmitted by the clutch, thereby moving the movable table;
a rotational direction of the high-speed motor unit that is rotated in a direction opposite to the rotational direction of the movable table when the movable table is moved downward in the high-torque mode; The control device includes:
The bending machine according to claim 1 , wherein the reversal control is performed when the load for bending the workpiece is low, the load being lower than a predetermined threshold value. The control device includes:
3. The bending machine according to claim 2, wherein, in the case of high-load bending where the load for bending the workpiece is equal to or greater than the threshold value, assist control is performed to drive the high-speed motor unit in a rotational direction when moving the movable table downward. The high-speed motor unit includes a first drive motor,
The bending machine according to claim 1 , wherein the pressure motor unit includes a second drive motor and a reducer that reduces and outputs a torque of the second drive motor. The power transmission mechanism includes:
a drive pulley to which the high-speed motor unit and the pressure motor unit are respectively connected;
A driven pulley connected to the conversion mechanism;
a belt stretched between the driving pulley and the driven pulley,
The bending machine according to claim 1 , wherein the high-speed motor unit is coaxially arranged on the opposite side of the pressure motor unit with the drive pulley therebetween. The power transmission mechanism includes:
a first drive pulley to which the high-speed motor unit is connected;
a second drive pulley to which the pressure motor unit is connected;
A driven pulley connected to the conversion mechanism;
a first belt stretched between the first driving pulley and the driven pulley;
The bending machine according to claim 1 , further comprising: a second belt stretched between the second driving pulley and the driven pulley.

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