Bending machine

Abstract

To improve the controllability of a movable table in a press brake.SOLUTION: The press brake 1 includes a table sensor 32 that outputs a position signal corresponding to the position of the movable table in the vertical direction, a motor shaft sensor 30 that outputs a motor shaft signal corresponding to the rotation of the motor shaft of the drive motor 26, and an output shaft sensor 31 that outputs an output shaft signal corresponding to the rotation of the output shaft of the speed reducer. The press brake 1 includes an NC device 100 that outputs a rotation command of the drive motor 26 based on a position signal and a target position of the movable table, and a motor driver 200 that controls a drive current supplied to the drive motor 26 based on the rotation command, a motor shaft signal, and an output shaft signal.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a bending machine. [Background technology]

[0002] A press brake, an example of a bending machine, moves a movable table up and down relative to a fixed table to bend a workpiece using dies attached to each table. The bending machine includes a drive unit including an electric motor and a reducer, and a conversion mechanism that converts the rotational motion of the drive unit into linear motion along the up and down direction to move the movable table up and down.

[0003] For example, Patent Document 1 discloses a structure in which a rotary encoder is directly connected to the drive shaft of a servo motor. According to this structure, the bending machine includes a rotary encoder that is pre-installed in the servo motor and a rotary encoder that is directly connected to the drive shaft of the servo motor. The two rotary encoders enable monitoring of the table position in the bending machine, thereby improving safety in the event of a rotary encoder failure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-141674 Summary of the Invention [Problem to be solved by the invention]

[0005] The power generated by the drive motor is transmitted to the conversion mechanism via mechanical elements such as gears. There is a slight gap between the mechanical elements that engage with each other in the direction of movement. This gap can cause the mechanical elements to move unintentionally, reducing the controllability of the movable table. [Means for solving the problem]

[0006] One aspect of one or more embodiments is a bending machine comprising: a movable table arranged opposite a fixed table in the vertical direction; a drive unit including a drive motor and a reducer that decelerates and outputs the rotation of the drive motor; a conversion mechanism that moves the movable table in the vertical direction by converting the rotational motion of the rotation input part into linear motion along the vertical direction; a transmission member that is stretched between the output shaft of the reducer and the rotation input part of the conversion mechanism and transmits the power of the rotational motion of the reducer; a table sensor that outputs a position signal in accordance with the vertical position of the movable table; a motor shaft sensor that outputs a motor shaft signal in accordance with the rotation of the motor shaft of the drive motor; an output shaft sensor that outputs an output shaft signal in accordance with the rotation of the output shaft of the reducer; a host controller that outputs a rotation command for the drive motor based on the position signal and a target position of the movable table; and a motor driver that controls the drive current supplied to the drive motor based on the rotation command, the motor shaft signal, and the output shaft signal. [Effects of the Invention]

[0007] According to one or more embodiments of the bending machine, it is possible to improve the controllability of the movable table. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a front view schematically showing the structure of a press brake according to this embodiment. [Figure 2] FIG. 2 is a block diagram showing the control system that controls the upper table. [Figure 3] FIG. 3 is an explanatory diagram showing the speed waveforms of the motor shaft and the output shaft. [Figure 4] FIG. 4 is an enlarged view of a main portion of the waveform (b1) in FIG. [Figure 5] FIG. 5 is an enlarged view of a main portion of the waveform (b2) in FIG. DETAILED DESCRIPTION OF THE INVENTION

[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] Hereinafter, the press brake 1 will be described in detail with reference to FIGS.

[0011] The press brake 1 is a bending machine that bends a plate-shaped workpiece 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, and left and right table drive devices 20.

[0012] The left and right side plates 2 are arranged opposite each other and spaced apart in the left-right direction.

[0013] 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.

[0014] 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.

[0015] 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. Each table drive device 20 is mainly composed of a drive unit 25, a timing belt 50, and a ball screw mechanism 55.

[0016] The drive unit 25 generates power for operating the ball screw mechanism 55. The drive unit 25 is made up of a drive motor 26 and a reducer 27.

[0017] The drive motor 26 is a device that is driven by electrical energy, such as a servo motor, and includes a rotating motor shaft 26a.

[0018] The motor shaft 26a of the drive motor 26 is connected to the reducer 27. The reducer 27 has an output shaft 27a that rotates at a predetermined reduction ratio relative to the rotation of the motor shaft 26a. The reducer 27 has a clutch mechanism. By switching the clutch mechanism, the reduction ratio of the reducer 27 can be switched between a first reduction ratio and a second reduction ratio that is greater than the first reduction ratio.

[0019] The clutch mechanism is, for example, a tooth clutch and includes multiple mechanical elements. Specifically, the clutch mechanism includes an annular first clutch member having multiple teeth arranged along the circumferential direction, an annular second clutch member having multiple teeth arranged along the circumferential direction, and an annular fixed clutch member that is movable axially between the first clutch member and the second clutch member. One surface of the fixed clutch member has multiple teeth arranged along the circumferential direction that can engage with the first clutch member when the fixed clutch member moves toward the first clutch member. The other surface of the fixed clutch member has multiple teeth arranged along the circumferential direction that can engage with the second clutch member when the fixed clutch member moves toward the second clutch member.

[0020] In this clutch mechanism, the reduction ratio of reducer 27 is set to a first reduction ratio when the fixed clutch member engages with one of the first and second clutch members, and the reduction ratio of reducer 27 is set to a second reduction ratio when the fixed clutch member engages with the other of the first and second clutch members. When the fixed clutch member and the first or second clutch member are engaged, a gap is created between the teeth of the fixed clutch member and the teeth of the first or second clutch member when viewed in the direction of movement (rotational direction) of the first and second clutch members. This allows the fixed clutch member and the first or second clutch member to be smoothly engaged.

[0021] The timing belt 50 is a transmission member that transmits the power of the rotational movement of the reducer 27 to the ball screw mechanism 55. The timing belt 50 is stretched between the output shaft 27a of the reducer 27 and a rotation input portion (a ball screw nut 56 described later) of the ball screw mechanism 55. However, the power may be transmitted by a method other than the timing belt 50.

[0022] The ball screw mechanism 55 is a conversion mechanism that converts the rotational motion of the rotation input part into linear motion, thereby moving the upper table 7 in the vertical direction. The ball screw mechanism 55 includes a ball screw nut 56, which is the rotation input part, 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 part. The ball screw nut 56 rotates in accordance with the rotation of the timing belt 50. The ball screw shaft 57 is threadedly engaged with the ball screw nut 56, and moves in the vertical direction as the ball screw nut 56 rotates forward and backward.

[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 that passes through the upper table 7 in the front-to-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.

[0024] 2, the press brake 1 includes an NC (Numerical Control) device 100 and a motor driver 200 as a control system for vertically moving an upper table of the press brake 1. The NC device 100 is a higher-level controller for the motor driver 200, which serves as a lower-level controller.

[0025] The press brake 1 is provided with a motor shaft sensor 30, an output shaft sensor 31, and a table sensor 32 to detect information required for the control system.

[0026] The motor shaft sensor 30 is provided inside the drive motor 26 (see FIG. 1). The motor shaft sensor 30 detects the rotation (rotational speed in this embodiment) of the motor shaft 26a of the drive motor 26 and outputs a motor shaft signal corresponding to the rotation of the motor shaft 26a. The motor shaft sensor 30 may be, for example, a resolver having a rotor connected to the motor shaft 26a of the drive motor 26 and a stator as a magnetic body with a built-in coil. However, the configuration of the motor shaft sensor 30 is not limited to this.

[0027] The output shaft sensor 31 is attached to the output shaft 27a of the reducer 27 (see FIG. 1). The output shaft sensor 31 detects the rotation (rotational speed in this embodiment) of the output shaft 27a of the reducer 27 and outputs an output shaft signal corresponding to the rotation of the output shaft 27a. For example, the output shaft sensor 31 can be a linear encoder that includes a rotor that rotates together with the output shaft 27a and has multiple slits arranged in the circumferential direction, and a fixedly disposed sensor that detects the multiple slits. However, the configuration of the output shaft sensor 31 is not limited to this.

[0028] Table sensor 32 is disposed near upper table 7 (see FIG. 1). Table sensor 32 detects the vertical position of upper table 7 and outputs a position signal according to the position of upper table 7. For example, table sensor 32 can be a linear encoder that includes a fixedly disposed linear scale having multiple slits aligned in the vertical direction, and a sensor that moves in the vertical direction together with upper table 7 to detect the multiple slits. However, the configuration of table sensor 32 is not limited to this.

[0029] The NC device 100 is configured by 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. The various functions of the NC device 100 are realized by having the hardware processor execute programs stored in the memory.

[0030] The NC device 100 receives a position signal output from the table sensor 32. The NC device 100 has a profile that indicates the transition (speed) of the target position of the upper table 7 from the upper end position to the lower end position (stroke position). The NC device 100 calculates a rotation command (a rotation speed command in this embodiment) for the drive motor 26 based on the position signal and the target position of the upper table 7. Specifically, the NC device 100 calculates a rotation command for the drive motor 26 based on the position signal output from the table sensor 32 so that the position of the upper table 7 becomes the target position. In other words, the NC device 100 feedback-controls the drive motor 26 so that the position of the upper table 7 becomes the target position. The NC device 100 outputs the calculated rotation command to the motor driver 200.

[0031] The motor driver 200 controls the drive current supplied to the drive motor 26 .

[0032] The motor driver 200 receives as input a rotation command output from the NC device 100, a motor shaft signal output from the motor shaft sensor 30, and an output shaft signal output from the output shaft sensor 31. The motor driver 200 controls the drive current supplied to the drive motor 26 based on the rotation command, the motor shaft signal, and the output shaft signal. Specifically, the motor driver 200 feedback-controls the drive current based on the motor shaft signal and the output shaft signal so that the rotation of the drive motor 26 corresponds to the rotation command. In other words, the motor driver 200 feedback-controls the drive current so that not only the motor shaft 26a of the drive motor 26 but also the output shaft 27a of the reducer 27 corresponds to the rotation command.

[0033] The operation of the control system according to this embodiment will be described below with reference to Figures 3 to 5. Figure 3 shows various waveforms from when the movement of the upper table starts until it stops. In Figure 3, group (a) shows waveforms related to a control system according to a comparative example, i.e., a control system in which only the motor shaft signal is fed back to the motor driver 200. On the other hand, group (b) shows waveforms related to the control system according to this embodiment, i.e., a control system in which the motor shaft signal and the output shaft signal are each fed back to the motor driver 200.

[0034] In group (a), waveform (a1) shows the waveform of motor shaft 26a of drive motor 26. In waveform (a1), "Lmt" shows the rotation command for motor shaft 26a, and "Lma" shows the motor shaft signal of motor shaft sensor 30, i.e., the actual rotation speed of motor shaft 26a. Waveform (a2) shows the waveform of output shaft 27a of reducer 27. In waveform (a2), "Lot" shows the rotation command for output shaft 27a (= rotation command for motor shaft 26a), and "Loa" shows the output shaft signal of output shaft sensor 31, i.e., the actual rotation speed of output shaft 27a.

[0035] In group (b), waveform (b1) shows the waveform of the motor shaft 26a of the drive motor 26. In waveform (b1), "Lmt" indicates the rotation command for the motor shaft 26a, and "Lmb" indicates the motor shaft signal of the motor shaft sensor 30, i.e., the actual rotation speed of the motor shaft 26a. For comparison, waveform (b1) also shows the actual rotation speed Lma of the motor shaft 26a in waveform (a1). Waveform (b2) shows the waveform of the output shaft 27a of the reducer 27. In waveform (b2), "Lot" indicates the rotation command for the output shaft 27a (= the rotation command for the motor shaft 26a), and "Lob" indicates the output shaft signal of the output shaft sensor 31, i.e., the actual rotation speed of the output shaft 27a. For comparison, waveform (b2) also shows the actual rotation speed Loa of the output shaft 27a in waveform (a2).

[0036] When the upper table 7 moves, a drive current is supplied from the motor driver 200 to the drive motor 26 in response to a rotation command from the NC device 100. As shown in waveform (a1), the motor shaft 26a of the drive motor 26 rotates to follow the rotation command Lmt.

[0037] A gap exists between the mechanical elements of the reducer 27, specifically, the teeth of the clutch member. As shown in waveform (a2), even if the motor shaft 26a of the drive motor 26 rotates, there is a state in which the output shaft 27a of the reducer 27 does not start moving until the gap is closed. Because the NC device 100 receives a position signal from the table sensor 32, the NC device 100 outputs a rotation command that takes into account the deviation between the position of the upper table 7 and the target position so as to eliminate this deviation. However, because feedback is performed by the NC device 100 and the motor driver 200 as a whole, a response time is required. This results in a significant delay in the start of movement of the output shaft 27a, reducing the controllability of the upper table 7.

[0038] In contrast, in the control system of this embodiment, the rotation of the output shaft 27a of the reducer 27 is detected by the output shaft sensor 31, and the rotation of the output shaft 27a is fed back to the motor driver 200. By detecting the delay in the rotation of the output shaft 27a relative to the rotation command, it is possible to correct the operation of the drive motor 26. This correction causes the drive motor 26 to rotate faster, as shown in waveform (b1) in Fig. 3 and Fig. 4. Fig. 4 is an enlarged view of a main portion of waveform (b1) in Fig. 3.

[0039] As the drive motor 26 rotates faster, the gaps between the teeth of the clutch member close earlier, and the output shaft 27a also starts to rotate earlier. This minimizes the delay in the output shaft 27a, as shown in waveform (b2) in Figure 3 and in Figure 5. Figure 5 is an enlarged view of a key portion of waveform (b2) in Figure 3.

[0040] As described above, in this embodiment, the press brake 1 includes an upper table 7 disposed vertically opposite the lower table 5, and a drive unit 25 including a drive motor 26 and a reducer 27 that reduces the rotation of the drive motor 26 before outputting the reduced rotation. The press brake 1 also includes a ball screw mechanism 55 that converts the rotational motion of a ball screw nut 56 into linear motion along the vertical direction to move the upper table 7 vertically, and a timing belt 50 that is stretched between an output shaft 27a of the reducer 27 and the ball screw nut 56 of the ball screw mechanism 55 and transmits the power of the rotational motion of the reducer 27. The press brake 1 also includes a table sensor 32 that outputs a position signal corresponding to the vertical position of the upper table 7, a motor shaft sensor 30 that outputs a motor shaft signal corresponding to the rotation of the motor shaft 26a of the drive motor 26, and an output shaft sensor 31 that outputs an output shaft signal corresponding to the rotation of the output shaft 27a of the reducer 27. The press brake 1 includes an NC device 100 that outputs a rotation command for the drive motor 26 based on a position signal and a target position of the upper table 7, and a motor driver 200 that controls the drive current supplied to the drive motor 26 based on the rotation command, a motor shaft signal, and an output shaft signal.

[0041] In this press brake 1, the NC device 100 calculates a rotation command for the drive motor 26 based on the position signal so that the position of the upper table 7 becomes a target position. Also, the motor driver 200 feedback controls the drive current based on the motor shaft signal and the output shaft signal so that the rotation of the drive motor 26 becomes the rotation command.

[0042] According to this configuration, the rotation of the output shaft 27a of the reducer 27 is detected by the output shaft sensor 31, and the rotation of the output shaft 27a is directly fed back to the motor driver 200. By detecting a delay in the rotation of the output shaft 27a relative to a rotation command, the operation of the drive motor 26 can be corrected. As a result, if a delay occurs in the rotation of the output shaft 27a, the drive motor 26 rotates faster. Furthermore, since the rotation of the output shaft 27a is directly fed back to the motor driver 200, the drive motor 26 can be controlled quickly. As the drive motor 26 rotates faster with good responsiveness, the gap between the teeth of the clutch member is quickly closed, and the output shaft 27a starts moving quickly. As a result, the delay in the output shaft 27a can be minimized, thereby preventing a decrease in controllability of the upper table 7.

[0043] In this embodiment, an output shaft sensor 31 is provided on the output shaft 27a of the reducer 27, and an output shaft signal obtained from this output shaft sensor 31 is fed back to the motor driver 200. Alternatively, it is possible to feed back a position signal from the table sensor 32 to the motor driver 200 instead of the output shaft signal. However, this method incorporates the position signal into the control loop of the motor driver 200, and the position of the upper table 7 is controlled by the motor driver 200. On the other hand, in this embodiment, the output shaft signal from the output shaft sensor 31 is directly fed back to the motor driver 200, allowing the drive unit 25 to correct any delays that occur in the drive unit 25 itself. Therefore, the NC device 100 only needs to calculate a rotation command by looking only at the table position, without considering the clearance of the reducer 27. This allows the NC device 100 to achieve versatile control. Additionally, the method of directly feeding back to the motor driver 200 requires the motor driver 200 to simply control the drive current according to the feedback amount, thereby providing more responsive control than a method of performing feedback via the NC device 100 and the motor driver 200 as a whole. This makes it possible to prevent a decrease in controllability of the upper table 7.

[0044] In the press brake 1 of this embodiment, the output shaft 27a of the reducer 27 and the ball screw nut 56 of the ball screw mechanism 55 are not directly connected, but rather power is transmitted between them via the timing belt 50. Therefore, the output shaft sensor 31 can be attached to the output shaft 27a of the reducer 27. Since the output shaft sensor 31 can directly monitor the output shaft 27a of the reducer 27, the delay of the output shaft 27a relative to the motor shaft 26a can be accurately monitored. In a structure in which the output shaft 27a of the reducer 27 and the ball screw nut 56 of the ball screw mechanism 55 are directly connected, a sensor cannot be attached to the output shaft 27a, and rotation can only be detected at a position distant from the output shaft 27a. In this case, accuracy is reduced compared to a method in which the output shaft 27a is directly monitored. Therefore, the method described in this embodiment can suppress a decrease in controllability of the upper table 7.

[0045] In this embodiment, the output shaft sensor 31 is a rotary encoder, and the motor shaft sensor 30 is a resolver. A resolver is a robust and durable sensor. Therefore, it can be used as a reliable motor shaft sensor 30 mounted in the drive motor 26.

[0046] 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, and various alternative embodiments, implementations and operating techniques will become apparent to those skilled in the art from this embodiment. [Explanation of symbols]

[0047] 1. Press brake 2 side plates 5 Lower table (fixed table) 7 Upper table (movable table) 20 Table drive device 25 Drive Unit 26 Drive motor 26a Motor shaft 27 Reducer 27a Output shaft 30 Motor shaft sensor 31 Output shaft sensor 32 Table Sensor 50 Timing belt (transmission member) 55 Ball screw mechanism (conversion mechanism) 56 Ball screw nut 57 Ball screw shaft 100 NC unit (host controller) 200 motor drivers

Claims

1. a movable table disposed opposite to the fixed table in the vertical direction; a drive unit including a drive motor and a reducer that reduces the rotation of the drive motor and outputs the reduced rotation; a conversion mechanism that converts the rotational motion of a rotation input unit into linear motion along the vertical direction, thereby moving the movable table in the vertical direction; a transmission member that is hung between the output shaft of the reducer and the rotation input portion of the conversion mechanism and transmits the power of the rotational movement of the reducer; a table sensor that outputs a position signal corresponding to the vertical position of the movable table; a motor shaft sensor that outputs a motor shaft signal corresponding to the rotation of the motor shaft of the drive motor; an output shaft sensor that outputs an output shaft signal corresponding to the rotation of the output shaft of the reducer; a host controller that outputs a rotation command for the drive motor based on the position signal and a target position of the movable table; a motor driver that controls a drive current to be supplied to the drive motor based on the rotation command, the motor shaft signal, and the output shaft signal; Bending machine.

2. The upper controller calculating the rotation command for the drive motor based on the position signal so that the position of the movable table reaches the target position; The motor driver feedback-controlling the drive current based on the motor shaft signal and the output shaft signal so that the rotation of the drive motor conforms to the rotation command; The bending machine according to claim 1.

3. the output shaft sensor is an encoder; The motor shaft sensor is a resolver.

3. The bending machine according to claim 1 or 2.

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