SERVO PRESS, CONTROL METHOD AND PROGRAM

Abstract

Servo press (1) comprising: a plunger (50) configured to move up and down; a servomotor (30) configured to move the plunger (50) up and down; an encoder (31) which is arranged on the servo motor (30); a plunger position detection unit (33) configured to detect a position of the plunger (50) based on an output signal from the encoder (31); an adjustment unit (13) which is configured to set a position condition for the plunger (50); a detection element (80) configured to detect a stop position of the plunger (50), wherein the detection element (80) is a linear encoder (80) located at the stop position of the plunger (50); a detection unit (14) configured to detect a detection value of the detection element (80) at the stop position of the plunger (50); a reference acquisition value storage unit (15) configured to store the acquisition value detected by the acquisition value detection unit (14) prior to a series of operations on a workpiece (70); a machining value storage unit (16) which is configured to overwrite the measurement value detected by the measurement value detection unit (14) in the series of machining operations on the workpiece (70); a correction value calculation unit (17) configured to calculate a correction value based on a reference acquisition value in the reference acquisition value storage unit (15) and an edit acquisition value in the edit acquisition value storage unit (16); and a servo motor control unit (19) configured to control the servo motor (30) on the basis of the plunger position detected by the plunger position detection unit (33), the set plunger position and the correction value calculated by the correction value calculation unit (17), and a temperature sensor (101) configured to detect the temperature around the plunger (50), wherein the servo motor control unit (19), when temperature data detected on the basis of a measurement from the temperature sensor (101) are greater than previously set temperature data, transmits a signal to the correction value calculation unit (17) instructing a calculation of a correction value and performs the control of the servo motor (30) in a next machining cycle on the basis of the ram position detected by the ram position detection unit (33), the set ram position and the correction value calculated by the correction value calculation unit (17) at a time when the ram (50) reaches the stop position.

Description

Technical area

[0001] The present invention relates to a servo press capable of performing a pressing operation with high accuracy while responding to mechanical changes due to thermal expansion, and a control method and program. State of the art

[0002] As is typically evident, electronic products have become increasingly technically sophisticated in recent years, and components for such products require extremely high precision. This also applies to pressing, and various technological improvements have been introduced to meet these demands. For example, extremely precise processing that cannot be achieved with a conventional hydraulic press is now performed by a servo motor-driven servo press.

[0003] For example, PTL 1 discloses a technique relating to a press driven by a servo motor and stroke-controlled with a control pattern in which a slide is set. This is a control method called semi-closed-loop control for controlling by monitoring an encoder of the servo motor, as described in Fig. 9 is illustrated. Literature listPatent literature

[0004] PTL 1: Publication of Unexamined Japanese Patent Application No. JP H02- 224 898 A

[0005] Japanese patent application No. JP 2002-192399 A relates to a correction method for correcting the bottom dead center position of a ram of a servo press when no pressing operation is taking place. The ram is raised and lowered with the aid of a servo motor, which drives a spindle mechanism. To detect the position of the ram, the servo press is equipped with an encoder, which acts as a detection device to detect the position of the ram over the entire stroke of the ram. The encoder is mechanically connected to the servo motor and detects the angle of rotation of the servo motor's drive shaft. The position of the ram is calculated from the pitch of the spindle mechanism. Furthermore, the servo press has a displacement sensor for detecting the position, i.e., the position of the ram, with greater accuracy than the encoder.The displacement sensor is located in the lower punch near the bottom dead center of the ram in order to be able to correct detection errors due to temperature changes.

[0006] Japanese patent application No. JP 2000-280100 A relates to a servo press with a position detector for correcting the detection of the bottom dead center position of the ram due to frame deformations and temperature influences. The ram is driven by a servo motor via the spindle mechanism, which in turn is operated by a controller. Located in the lower part of the frame, i.e., in the mold, are a sensor for detecting the position of the bottom dead center of the ram and a temperature sensor for detecting the temperature of the press mold. The temperature change is measured in advance during the detection of the bottom dead center and added to the bottom dead center correction amount or transmitted to the controller.

[0007] For further known prior art, reference is made to European patent application No. EP 1 537 988 A2. SUMMARY OF THE INVENTIONTechnical Problem

[0008] However, there is a problem that the semi-closed loop control is not able to respond to a mechanical change such as thermal expansion because the control is done by monitoring an encoder of a servo motor, and this seriously affects the accuracy in pressing.

[0009] Thus, the present invention was made in view of the above-mentioned problems, and aims to provide a servo press capable of pressing with high accuracy while responding to a mechanical change due to thermal expansion, and a control method and program. Solution to the problem

[0010] In view of the above problems, the present invention proposes the following.

[0011] (1) The present invention proposes a servo press including: a slide configured to move up and down; a servo motor configured to move the slide up and down; an encoder arranged on the servo motor; a slide position detection unit configured to detect a position of the slide based on an output signal from the encoder; a setting unit configured to set a position condition of the slide; a detection element configured to detect a stop position of the slide, the detection element being a linear encoder arranged at the stop position of the slide; a detection value detection unit configured to detect a detection value of the detection element at the stop position of the slide; a reference detection value storage unit configuredto store the detection value detected by the detection value detection unit before a series of machining operations on a workpiece; a machining detection value storage unit configured to overwrite the detection value detected by the detection value detection unit in the series of machining operations on the workpiece; a correction value calculation unit configured to calculate a correction value based on a reference detection value in the reference detection value storage unit and a machining detection value in the machining detection value storage unit; and a servo motor control unit configured to control the servo motor based on the ram position detected by the ram position detection unit, the ram position that has been adjusted, and the correction value calculated by the correction value calculation unit, and a temperature sensor configuredto detect the temperature around the ram, wherein the servo motor control unit, when temperature data detected based on a measured value of the temperature sensor is greater than predetermined temperature data, transmits a signal instructing calculation of a correction value to the correction value calculation unit and performs control of the servo motor in a next machining cycle based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit at a time when the ram reaches the stop position.

[0012] According to the invention, before the series of machining operations on a workpiece, the servo motor is controlled to move the slide to the stop position based on the slide position detected by the slide position detection unit and the set slide position. The detection value of the detection element at the stop position of the slide is detected, and the detected detection value is stored in the reference detection value storage unit. Next, in the series of machining operations, the detection value of the detection element at the stop position of the slide is detected, and the detected detection value is stored in the machining detection value storage unit. Furthermore, the correction value is calculated based on the reference detection value in the reference detection value storage unit and the machining detection value in the machining detection value storage unit.Then, in the next machining, the servo motor is controlled based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit. When temperature data detected based on a measured value of the temperature sensor is greater than predetermined temperature data, the servo motor control unit transmits a signal instructing calculation of a correction value to the correction value calculation unit, and performs control of the servo motor in a next machining cycle based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit at a time point when the ram reaches the stop position.Specifically, the thermally expanded length of the ram (punch) is measured using a detection element separated from a servo system to correct an operating gap. The position of the detection element is registered at an ideal workpiece reference position as reference data. Furthermore, a travel amount for one operating stroke is performed by the servo motor's encoder. The difference from the reference position registered each time for the travel amount is calculated and reflected in the next operation as a correction value. This makes it possible to perform highly accurate pressing while responding to mechanical changes due to thermal expansion, which is a problem in semi-closed-loop control.

[0013] (2) The present invention proposes the servo press (1), wherein the detecting element is a linear encoder.

[0014] According to the invention, the detection element is the linear encoder. In particular, since the stop position of the plunger (stamp) is read by the linear encoder, the travel range to be measured is smaller compared to full-closed-loop control. Thus, it is possible to provide a cost-effective system by using the linear encoder with a smaller measuring range.

[0015] (3) The present invention proposes the servo press (1) and (2) such that the linear encoder is arranged at the stop position of the ram.

[0016] According to the invention, the linear encoder is arranged at the stop position of the ram. In particular, by arranging the linear encoder at the stop position of the ram (punch), it is possible to position a workpiece with greater accuracy.

[0017] (4) The present invention proposes the servo press (1), (2) and (3) such that, when temperature data detected based on a measured value of the temperature sensor is larger than predetermined temperature data, the servo motor control unit transmits a signal instructing calculation of a correction value to the correction value calculation unit and performs control of the servo motor in a next machining cycle based on the ram position detected by the ram position detection unit, the set ram position and the correction value calculated by the correction value calculation unit at a time point when the ram reaches the stop position.

[0018] According to the invention, when temperature data detected based on a measured value of the temperature sensor is greater than predetermined temperature data, the servo motor control unit transmits the signal instructing calculation of the correction value to the correction value calculation unit, and performs control of the servo motor in the next machining cycle based on the position of the ram (punch) detected by the ram position detection unit, the set position of the ram (punch), and the correction value calculated by the correction value calculation unit at a time when the ram (punch) reaches the stop position. In particular, since the linear encoder is an independent encoder, it is not necessary to constantly read the position of the ram (punch). It is sufficient if the reading is performed at least when the ram (punch) stops at the ram (punch) stop position.Thus, it is possible to minimize processing effort and the like that may arise due to the presence of the linear encoder.

[0019] (5) The present invention proposes the servo press (1), (2), (3) and (4) including: a temperature sensor configured to detect the temperature around the slide, wherein the servo motor control unit, when temperature data detected based on a measured value of the temperature sensor is greater than predetermined temperature data, transmits the signal instructing calculation of a correction value to the correction value calculation unit and performs control of the servo motor in a next machining cycle based on the slide position detected by the slide position detection unit, the set slide position and the correction value calculated by the correction value calculation unit at which the slide reaches the stop position.

[0020] According to the invention, the servo press includes: the temperature sensor configured to detect the temperature around the ram (punch); wherein, when the temperature data detected based on the measured value of the temperature sensor is higher than predetermined temperature data, the servo motor control unit transmits the signal instructing calculation of the correction value to the correction value calculation unit, and performs control of the servo motor in the next machining cycle based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit at a time when the ram (punch) reaches the stop position. In particular, since the linear encoder is an independent encoder, it is not necessary to constantly read the position of the ram (punch).It is sufficient if reading is performed at least when the plunger (punch) stops at the plunger (punch) stop position, at a time when the plunger (punch) reaches the stop position, when the temperature data detected based on the measured value of the temperature sensor is greater than the previously set temperature data. Thus, it is possible to minimize the machining workload and the like that may arise due to the presence of the linear encoder.

[0021] (6) The present invention proposes the servo press (1), (2), (3), (4) and (5) including: a threshold value storage unit configured to store a threshold value for a magnitude of the correction value, wherein the servo motor control unit, when the correction value calculated by the correction value calculation unit is larger than the threshold value stored in the threshold value storage unit, performs the control of the servo motor in a next machining cycle based on the ram position detected by the ram position detection unit, the set ram position and the correction value calculated by the correction value calculation unit at a time point when the ram reaches the stop position.

[0022] According to the invention, the servo press includes: the threshold value storage unit configured to store the threshold value for a magnitude of the correction value; wherein, when the correction value calculated by the correction value calculation unit is greater than the threshold value stored in the threshold value storage unit, the servo motor control unit performs control of the servo motor in the next machining cycle based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit at a time point when the ram reaches the stop position. In particular, since the linear encoder is an independent encoder, it is not necessary to constantly read the position of the ram (punch).It is sufficient if the reading is performed at least when the slide (punch) stops at the stop position, at the time when the slide (punch) reaches the stop position. Furthermore, when the position of the slide (punch) is read to calculate the correction value, this calculated correction value is reflected in the next machining cycle only if it is greater than the predetermined threshold. Thus, it is possible to minimize the machining workload and the like that may arise due to the presence of the linear encoder.

[0023] (7) The present invention proposes a control method for a servo press, including: a slide configured to move up and down; a servo motor configured to move the slide up and down; an encoder arranged on the servo motor; a slide position detection unit; a setting unit configured to set a position condition for the slide; a detection element configured to detect a stop position of the slide, the detection element being a linear encoder arranged at the stop position of the slide; a detection value detection unit configured to detect a detection value of the detection element at the stop position of the slide; a reference detection value storage unit; a machining detection value storage unit; a correction value calculation unit;and a servo motor control unit, and a temperature sensor configured to detect the temperature around the ram, the method including: a first step in which, before a series of machining operations on a workpiece, the servo motor control unit moves the ram to the stop position by controlling the servo motor based on the ram position detected by the ram position detection unit and the ram position that has been set; a second step in which the detection value detection unit detects the detection value of the detection element at the stop position of the ram and stores the detected detection value in the reference detection value storage unit;a third step in which the detection value detection unit detects the detection value of the detection element at the stop position of the slide in the series of machining operations and stores the detected detection value in the machining detection value storage unit; a fourth step in which the correction value calculation unit calculates a correction value based on a reference detection value in the reference detection value storage unit and a machining detection value in the machining detection value storage unit;and a fifth step in which the servo motor control unit controls the servo motor in a next machining step based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit. When temperature data detected based on a measured value of the temperature sensor is greater than predetermined temperature data, the servo motor control unit transmits a signal instructing calculation of a correction value to the correction value calculation unit, and performs control of the servo motor in a next machining cycle based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit at a time point when the ram reaches the stop position.

[0024] According to the invention, before the series of machining operations on a workpiece, the servo motor is controlled to move the slide to the stop position based on the slide position detected by the slide position detection unit and the set slide position. The detection value of the detection element at the stop position of the slide is detected, and the detected detection value is stored in the reference detection value storage unit. Next, in the series of machining operations, the detection value of the detection element at the stop position of the slide is detected, and the detected detection value is stored in the machining detection value storage unit. Furthermore, the correction value is calculated based on the reference detection value in the reference detection value storage unit and the machining detection value in the machining detection value storage unit.In the next machining step, the servo motor is then controlled based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit. When temperature data detected based on a measured value of the temperature sensor is greater than predetermined temperature data, the servo motor control unit transmits a signal instructing calculation of a correction value to the correction value calculation unit, and performs control of the servo motor in a next machining cycle based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit at a time point when the ram reaches the stop position.Specifically, the thermally expanded length of the ram (punch) is measured using a detection element separated from a servo system to correct an operating gap. The position of the detection element is registered at an ideal workpiece reference position as reference data. Furthermore, a travel amount for one operating stroke is performed by the servo motor's encoder. The difference from the reference position registered each time for the travel amount is calculated and reflected in the next operation as a correction value. This makes it possible to perform highly accurate pressing while responding to mechanical changes due to thermal expansion, which is a problem in semi-closed-loop control.

[0025] (8) The present invention proposes a program for causing a computer to execute a control method for a servo press, including: a slide configured to move up and down; a servo motor configured to move the slide up and down; an encoder arranged on the servo motor; a slide position detection unit; a setting unit configured to set a position condition for the slide; a detection element configured to detect a stop position of the slide, the detection element being a linear encoder arranged at the stop position of the slide; a detection value detection unit configured to detect a detection value of the detection element at the stop position of the slide; a reference detection value storage unit; a machining detection value storage unit;a correction value calculation unit and a servo motor control unit and a temperature sensor configured to detect the temperature around the ram, wherein the program causes the computer to execute the method including: a first step in which, before a series of machining operations on a workpiece, the servo motor control unit moves the ram to the stop position by controlling the servo motor based on the ram position detected by the ram position detection unit and the set ram position; a second step in which the detection value detection unit detects the detection value of the detection element at the stop position of the ram and stores the detected detection value in the reference detection value storage unit;a third step in which the detection value detection unit detects the detection value of the detection element at the stop position of the slide in the series of machining operations and stores the detected detection value in the machining detection value storage unit; a fourth step in which the correction value calculation unit calculates a correction value based on a reference detection value in the reference detection value storage unit and a machining detection value in the machining detection value storage unit;and a fifth step in which the servo motor control unit controls the servo motor in a next machining step based on the ram position detected by the ram position detection unit, the ram position that has been adjusted, and the correction value calculated by the correction value calculation unit. When temperature data detected based on a measured value of the temperature sensor is greater than predetermined temperature data, the servo motor control unit transmits a signal instructing calculation of a correction value to the correction value calculation unit, and performs control of the servo motor in a next machining cycle based on the ram position detected by the ram position detection unit, the adjusted ram position, and the correction value calculated by the correction value calculation unit at a time point when the ram reaches the stop position.

[0026] According to the invention, before the series of machining operations on a workpiece, the servo motor is controlled to move the slide to the stop position based on the slide position detected by the slide position detection unit and the set slide position. The detection value of the detection element at the stop position of the slide is detected, and the detected detection value is stored in the reference detection value storage unit. Next, in the series of machining operations, the detection value of the detection element at the stop position of the slide is detected, and the detected detection value is stored in the machining detection value storage unit. Furthermore, the correction value is calculated based on the reference detection value in the reference detection value storage unit and the machining detection value in the machining detection value storage unit.In the next machining step, the servo motor is then controlled based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit. When temperature data detected based on a measured value of the temperature sensor is greater than predetermined temperature data, the servo motor control unit transmits a signal instructing calculation of a correction value to the correction value calculation unit, and performs control of the servo motor in a next machining cycle based on the ram position detected by the ram position detection unit, the set ram position, and the correction value calculated by the correction value calculation unit at a time point when the ram reaches the stop position.Specifically, the thermally expanded length of the ram (punch) is measured using a detection element separated from a servo system to correct an operating gap. The position of the detection element is registered at an ideal workpiece reference position as reference data. Furthermore, a travel amount for one operating stroke is performed by the servo motor's encoder. The difference from the reference position registered each time for the travel amount is calculated and reflected in the next operation as a correction value. This makes it possible to perform highly accurate pressing while responding to mechanical changes due to thermal expansion, which is a problem in semi-closed-loop control. Advantageous effects of the invention

[0027] According to the invention, it is possible to ensure extremely precise pressing as an effect while reacting to mechanical changes due to thermal expansion, which is a problem in semi-closed-loop control.

[0028] According to the invention, it is possible to provide the effect of highly accurate pressing at low cost by providing the linear encoder separately from a servo system.

[0029] According to the invention, it is possible to provide, as an effect, positioning of a workpiece with greater accuracy by arranging the linear encoder at the stop position of the ram (punch).

[0030] Since the linear encoder according to the invention is an independent encoder, it is not necessary to constantly read the position of the plunger (punch). It is sufficient if the reading occurs at least when the plunger (punch) stops at the plunger (punch) stop position. This makes it possible to minimize machining costs and the like that may arise due to the presence of the linear encoder.

[0031] Since the linear encoder according to the invention is an independent encoder, it is not necessary to constantly read the position of the plunger (punch). It is sufficient if the reading is performed at least when the plunger (punch) stops at its stop position, at a time when the plunger (punch) reaches the stop position, when the temperature data detected based on the measured value of the temperature sensor is greater than the previously set temperature data. As a result, it is possible to minimize machining costs and the like that may arise due to the presence of the linear encoder.

[0032] Since the linear encoder according to the invention is an independent encoder, it is not necessary to constantly read the position of the slide (punch). It is sufficient if the reading is performed at least when the slide (punch) stops at the slide (punch) stop position, at a time when the slide (punch) reaches the stop position. Furthermore, when the position of the slide (punch) is read to calculate the correction value, the calculated correction value is reflected in the next machining cycle only if it is greater than the predetermined threshold. Thus, it is possible to minimize machining workload and the like that may arise due to the presence of the linear encoder. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Fig. 1 is a side view of a servo press according to a first embodiment of the present invention; Fig. 2 is an overall view of a structure and control of the servo press according to the first embodiment of the present invention; Fig. 3 is a functional block diagram of the servo press according to the first embodiment of the present invention; Fig. 4 is a flowchart of the control of a servo press according to the first embodiment of the present invention; Fig. 5 is a functional block diagram of the servo press according to a second embodiment of the present invention; Fig. 6 is a flowchart of the control of the servo press according to the second embodiment of the present invention; Fig. 7 is a functional block diagram of the servo press according to a third embodiment of the present invention; Fig. Fig. 8 is a flowchart of the control of a servo press according to the third embodiment of the present invention; and Fig. 9 is a functional block diagram according to the conventional example. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0035] It should be noted that components in this embodiment can be replaced with existing components as needed, and variations including combinations with other existing components are also possible. Therefore, the description of this embodiment does not limit the scope of the invention as defined by the claims. First embodiment

[0036] Hereinafter, the first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 4 described.

[0037] As in Fig. 1, a servo press 1 according to this embodiment is configured by a press main body 20, a servo motor 30, a table 40 on which the press main body 20 is located, a punch 50 that moves up and down with respect to the press main body 20, a shaft 60, a workpiece 70, a linear encoder 80, and a workpiece fixing base 90 for fixing a workpiece.

[0038] The servo press 1 is mounted on a frame (not shown), and the table 40 is located below the frame. The workpiece fixing base 90 is horizontally disposed in the table 40, and the workpiece 70 is fixed to an upper surface of the workpiece fixing base 90. Furthermore, the punch 50 and the shaft 60 at a tip portion of the punch 50 are inserted into the table 40 through the press main body 20 and move up and down.

[0039] The punch 50 is connected to and driven by the servo motor 30 via a power conversion element and a rotation transmission element, both of which are not shown. The servo motor 30 is further connected to a control device, which will be described later. The punch 50 driven by the servo motor 30 is controlled based on a control pattern input to the control device or automatically set based on an input machining condition. With this control, the punch 50 can be moved from a lifting point (home position) to a lowering point (stop position) to perform pressing, and an intermediate point is defined between the lifting point (home position) and the lowering point (stop position). More precise machining can be performed by setting a different speed from the intermediate point to the lowering point (stop position). Overall configuration and control

[0040] An overall configuration and control of the servo press according to this embodiment will be described with reference to Fig. 2 and Fig. 3 described.

[0041] The servo press 1 according to this embodiment is, as shown in Fig. 2, is constituted by a control device 10, a controller 11 constituting a control device 10, a driver 12, an adjusting unit 13, a roller 21, a belt 22, a ball screw 23, the servo motor 30, an encoder 31, the punch 50, the workpiece 70, the linear encoder 80 and the workpiece fixing base 90.

[0042] Mounted above the frame are the servo motor 30 as the power source for the servo press 1 and the roller 21 as the rotation transmission element for converting the rotational force of the servo motor 30 into a reciprocating motion. The servo motor 30 is mounted on the encoder 31 for detecting the rotational speed, and the rotational speed of the servo motor 30 is controlled by the control device 10, which controls the current supplied to the servo motor 30. The rotational force of the servo motor 30 is transmitted to the ball screw 23 through the belt 22 as the rotation transmission element. The servo motor 30 can be either an AC motor or a DC motor.

[0043] Further, the rotation transmission member is exemplified by, but not limited to, the roller 21, and may be a chain or a gear. Furthermore, the rotation transmission member may be directly coupled to an output shaft of the servo motor 30. Further, the energy conversion device is exemplified by, but not limited to, the ball screw 23, and may be a screw mechanism, a combination of a worm gear and a worm wheel, or a pinion and a rack. At a lower end of the ball screw 23, the punch 50 is fixed, which moves up and down in a position facing the workpiece fixing base 90, and pressing is performed on a workpiece (object to be machined) 70 by the punch 50, which moves down from an uppermost position (starting position) to a lowermost position (stopping position).Then, when the punch 50 has reached the lowest position (stop position), it moves upward to the uppermost position (start position), and the machining of the workpiece (object to be machined) 70 ends.

[0044] The encoder 31 is mounted in a predetermined position on the servo motor 30. The linear encoder 80 is preferably arranged at a stop position of the punch 50. In particular, the mounting position of the linear encoder 80 is determined based on an ideal machining position of the workpiece 70 (a in Fig. 2) and data from the linear encoder 80 at this position is used as reference data. Note that b in Fig. 2 indicates an amount for the feed of the punch 50 to the workpiece 70.

[0045] The linear encoder 80 here is an element for detecting and outputting a position along a linear axis as position information, also referred to as a position encoder or a linear scale. The linear encoder is configured by a scale (scale marks) as a scale and a head (detector) for detecting the position information. An optical type that uses reflected light for detection uses a detection head fixed to the punch 50 and arranged in a position not shown facing the linear encoder 80. In other words, a sensor built into the detection head detects the position of the punch 50 based on the reference stop position of the punch 50 as a height, since the detection head moves up and down with respect to the fixed linear encoder 80 along with the vertical movement of the punch 50.Apart from the types mentioned above, there is a magnetic type that uses magnetism, an absolute type that performs absolute position measurement, and an incremental type that performs relative position measurement.

[0046] During pressing, values ​​such as the operating speed of the punch 50, a speed switching position, the lowest position (stop position), and the pressurizing time are set as control conditions via the setting unit 13. The set values ​​are displayed on a display unit (not shown). The display unit is configured by a setting switch and means such as a liquid crystal display screen or a cathode ray tube. The display unit is further arranged on switches for selecting an operation mode, such as operation and condition setting, and for instructing operation, such as automatic or manual operation.

[0047] Then, the control data input via the display unit is recorded and stored in a storage unit described later, and the stamp 50 is controlled according to previously installed workflows. The control device 10 is configured as a conventional computer or the like with functions such as data recording, calculation, data display, and data input / output. Functional blocks of the servo press

[0048] The servo press 1 according to this embodiment is, as shown in Fig. 3 illustrates, of the control device 10, a detection value detection unit 14 constituting the control device 10, a reference detection value storage unit 15, a machining detection value storage unit 16, a correction value calculation unit 17, a storage unit 18, a control unit 19, the servo motor 30, the encoder 31, a position detection unit 33, the punch 50, and the linear encoder 80.

[0049] The detection value detection unit 14 detects a detection value of the linear encoder 80 at the stop position of the punch 50 before a series of machining operations on the tool 70 and at a time when the punch 50 reaches the stop position, with a signal output from the control unit 19 serving as a trigger. The detection value detection unit 14 also detects the detection value of the linear encoder 80 at the stop position of the punch 50 during the series of machining operations on the tool 70 and at a time when the punch 50 reaches the stop position, with a signal output from the control unit 19 serving as a trigger.

[0050] The reference detection value storage unit 15 stores the detection value of the linear encoder 80 detected by the detection value detection unit 14 at the stop position of the punch 50 before the series of machining operations on the workpiece 70. The machining detection value storage unit 16 stores the detection value of the linear encoder 80 detected by the detection value detection unit 14 at the stop position of the punch 50 during the series of machining operations on the workpiece 70. The stored detection value is overwritten with a new detection value and stored.

[0051] The correction value calculation unit 17 calculates a correction value based on a reference detection value in the reference detection value storage unit 15 and a machining detection value in the machining detection value storage unit 16. The control unit 19 outputs a signal for instructing the calculation of a correction value to the correction value calculation unit 17 during the series of machining operations of the workpiece 70 and at a time when the punch 50 reaches the stop position, and executes control of the servo motor based on the ram position detected by the position detection unit 33, the set ram position, and the correction value calculated by the correction value calculation unit 17. The storage unit 18 stores a predetermined operating condition.

[0052] Here, it is preferable that the downward movement of the plunger 50 be subjected to motion control. In other words, high-speed approach control to a predetermined lowering position and low-speed probing control from the predetermined lowering position are performed. Specifically, an output torque is detected from the current of the servomotor command controlling the servomotor 30, and a change in the movement of the plunger 50 is detected as a change in the torque of the servomotor 30. Then, the predetermined lowering position is re-indicated based on the detected torque change signal. Control processes in the servo press

[0053] The control procedures of the servo press according to this embodiment will be described with reference to Fig. 4 described.

[0054] Before the series of machining operations on the workpiece 70, the control unit 19 moves the ram (punch) 50 to the stop position by controlling the servo motor 30 based on the position of the ram (punch) 50 detected by the position detection unit 33 and the set position of the ram (punch) 50 (step S110).

[0055] The detection value detection unit 14 detects the detection value of the detection element (linear encoder) 80 at the stop position of the plunger (punch) 50 and stores the detected detection value in the reference detection value storage unit 15 (step S120).

[0056] In the series of machining, the detection value detection unit 14 detects the detection value of the detection element (linear encoder) 80 at the stop position of the slide (punch) 50 and stores the detected detection value in the machining detection value storage unit 16 (step S130).

[0057] The correction value calculation unit 17 calculates a correction value based on a reference detection value in the reference detection value storage unit 15 and a machining detection value in the machining detection value storage unit 16 (step S140).

[0058] In the next machining operation, the control unit 19 controls the servo motor (step S150) based on the position of the plunger 50 detected by the position detection unit 33, the set position of the plunger 50, and the correction value calculated by the correction value calculation unit 17. Then, the machining continues from step S130 to step S150 ("No" at step S160) until the series of machining operations is completed. When the series of machining operations is completed, the entire machining operation is terminated ("Yes" at step S160).

[0059] According to this embodiment, as described above, it is possible to perform highly accurate pressing while responding to mechanical changes due to thermal expansion, which is a problem in semi-closed-loop control. Furthermore, by disposing the linear encoder separately from a servo system, it is possible to perform highly accurate pressing at low cost. Moreover, by disposing the linear encoder at the stop position of the slide (punch), it is possible to position a workpiece with greater accuracy. In addition, since the linear encoder is an independent encoder, it is not necessary to constantly read the position of the slide (punch). It is sufficient if reading is performed at least when the slide (punch) stops at its stop position. Thus, it is possible to minimize machining work and the like that may arise due to the presence of the linear encoder. Second embodiment

[0060] The second embodiment of the present invention will be described below with reference to Fig. 5 and Fig. 6 described. Functional blocks of the servo press

[0061] The servo press 1 according to this embodiment is, as shown in Fig. 5, the control device 100 is configured by a detection value detection unit 14 constituting the control device 100, a reference detection value storage unit 15, a machining detection value storage unit 16, a correction value calculation unit 17, a storage unit 18, a control unit 102, a temperature detection unit 101, a servo motor 30, an encoder 31, a position detection unit 33, a punch 50, and a linear encoder 80. Components with the same reference numerals as those in the first embodiment have the same functions, and detailed descriptions of such components will be omitted.

[0062] The temperature detection unit 101 detects the temperature around the punch 50. When the temperature data detected based on a value from the temperature sensor is greater than the predetermined temperature data, the control unit 102 transmits a signal instructing the calculation of a correction value to the correction value calculation unit 17 and performs control of the servo motor in a next machining cycle based on the position of the punch detected by the position detection unit 33, the set position of the punch, and the correction value calculated by the correction value calculation unit 17 at the time when the punch 50 reaches the stop position. Control processes of the servo press

[0063] The control procedures of the servo press according to this embodiment will be described with reference to Fig. 6 described.

[0064] Before the series of machining operations on the workpiece 70, the control unit 102 moves the ram (punch) 50 to the stop position by controlling the servo motor 30 based on the position of the ram (punch) 50 detected by the position detection unit 33 and the set position of the ram (punch) 50 (step S210).

[0065] The detection value detection unit 14 detects the detection value of the detection element (linear encoder) 80 at the stop position of the plunger (punch) 50 and stores the detected detection value in the reference detection value storage unit 15 (step S220).

[0066] In the series of machining, the detection value detection unit 14 detects the detection value of the detection element (linear encoder) 80 at the stop position of the slide (punch) 50 and stores the detected detection value in the machining detection value storage unit 16 (step S230).

[0067] The control unit 102 determines whether the temperature around the stamper 50 detected by the temperature detection unit 101 is higher than a predetermined temperature (step S240). At this time, if the control unit 102 determines that the temperature around the stamper 50 detected by the temperature detection unit 101 is lower than the predetermined temperature ("No" at step S240), the control unit 102 performs a normal control operation (step S250), and the processing proceeds to step S280.

[0068] On the other hand, when the control unit 102 determines that the temperature around the punch 50 detected by the temperature detection unit 101 is higher than the predetermined temperature ("Yes" at step S240), the correction value calculation unit 17 calculates a correction value based on a reference detection value in the reference detection value storage unit 15 and a machining detection value in the machining detection value storage unit 16 (step S260).

[0069] In the next machining operation, the control unit 102 controls the servo motor (step S270) based on the position of the plunger (punch) 50 detected by the position detection unit 33, the set position of the plunger (punch) 50, and the correction value calculated by the correction value calculation unit 17. Then, the machining continues from step S240 to step S270 ("No" at step S280) until the series of machining operations is completed. When the series of machining operations is completed, the entire machining operation is terminated ("Yes" at step S280).

[0070] According to this embodiment, as described above, it is possible to perform highly accurate pressing while responding to mechanical changes due to thermal expansion, which is a problem in semi-closed-loop control. Furthermore, since the linear encoder is an independent encoder, it is not necessary to constantly read the position of the slide (punch). It is sufficient if the reading is performed at least when the slide (punch) stops at its stop position, at a time when the slide (punch) reaches the stop position, when the temperature data detected based on the measured value of the temperature sensor is greater than the previously set temperature data. Thus, it is possible to minimize machining work and the like that may arise due to the presence of the linear encoder. Third embodiment

[0071] The third embodiment of the present invention will be described below with reference to Fig. 7 and Fig. 8 described. Functional blocks of the servo press

[0072] The servo press 1 according to this embodiment is, as shown in Fig. 7, the control device 110 is configured by a control device 110, a detection value detection unit 14 constituting the control device 110, a reference detection value storage unit 15, a machining detection value storage unit 16, a correction value calculation unit 17, a storage unit 18, a control unit 112, a threshold value storage unit 111, a servo motor 30, an encoder 31, a position detection unit 33, a punch 50, and a linear encoder 80. Components with the same reference numerals as those in the first and second embodiments have the same functions, and detailed descriptions of such components will be omitted.

[0073] The threshold storage unit 111 stores a threshold value previously determined for a magnitude of a correction value. If a correction value calculated by the correction value calculation unit 17 is greater than the threshold value stored in the threshold storage unit 111, the control unit 112 performs control of the servo motor in a next machining cycle based on the position of the plunger detected by the position detection unit 33, the set position of the plunger, and the correction value calculated by the correction value calculation unit 17 at the time when the plunger 50 reaches the stop position. Control processes of the servo press

[0074] The control procedures of the servo press according to this embodiment will be described with reference to Fig. 8 described.

[0075] Before the series of machining operations on the workpiece 70, the control unit 112 moves the ram (punch) 50 to the stop position by controlling the servo motor 30 based on the position of the ram (punch) 50 detected by the position detection unit 33 and the set position of the ram (punch) 50 (step S310).

[0076] The detection value detection unit 14 detects the detection value of the detection element (linear encoder) 80 at the stop position of the plunger (punch) 50 and stores the detected detection value in the reference detection value storage unit 15 (step S320).

[0077] In the series of machining operations, the detection value detection unit 14 detects the detection value of the detection element (linear encoder) 80 at the stop position of the slide (punch) 50 and stores the detected detection value in the machining detection value storage unit 16 (step S330). The correction value calculation unit 17 calculates a correction value based on a reference detection value in the reference detection value storage unit 15 and a machining detection value in the machining detection value storage unit 16 (step S340).

[0078] The control unit 112 determines whether the correction value calculated by the correction value calculation unit 17 is greater than the threshold value previously stored in the threshold value storage unit 111 (step S350). At this time, if the control unit 112 determines that the correction value calculated by the correction value calculation unit 17 is less than the threshold value previously stored in the threshold value storage unit 111 ("No" at step S350), the control unit 112 performs a normal control operation (step S360), and the processing proceeds to step S380.

[0079] On the other hand, if the control unit 112 determines that the correction value calculated by the correction value calculation unit 17 is greater than the threshold value previously stored in the threshold value storage unit 111 ("Yes" at step S350), it performs control of the servo motor in a next processing based on the position of the plunger (punch) 50 detected by the position detection unit 33, the set position of the plunger (punch) 50, and the correction value calculated by the correction value calculation unit 17 (step S370). Then, the processing continues from step S330 to step S370 ("No" at step S380) until the series of processing is completed. When the series of processing is completed, the entire processing is terminated ("Yes" at step S380).

[0080] According to this embodiment, as described above, it is possible to perform highly accurate pressing while responding to mechanical changes due to thermal expansion, which is a problem in semi-closed-loop control. Furthermore, since the linear encoder is an independent encoder, it is not necessary to constantly read the position of the slide (punch). It is sufficient if the reading is performed at least when the slide (punch) stops at its stop position, at a time when the slide (punch) reaches the stop position. Furthermore, when the position of the slide (punch) is read to calculate the correction value, the calculated correction value is reflected in the next machining cycle only if it is larger than the predetermined threshold. Thus, it is possible to minimize machining workload and the like that may arise due to the presence of the linear encoder.

[0081] It should be noted that it is possible to implement the servo press according to the present invention by recording its above-described control sequences on a medium readable by a computer system, and having the servo press read and execute the recording on the medium. Examples of the computer system here include an operating system and hardware such as peripherals.

[0082] When using the WWW (World Wide Web), examples of the "computer system" further include a web page providing environment (or display environment). Furthermore, the program can be transmitted from the computer system in which it is recorded in the recording device or the like to other computer systems via a transmission medium or a transmitted wave in the transmission medium. The "transmission medium" transmitting the program here refers to a medium that has the function of transmitting information, such as a network (communication network) such as the Internet, and a communication line (communication cable) such as a telephone line.

[0083] In addition, the program can implement some of the functions described above. Furthermore, the program can be a difference file (a difference program) that can implement the functions described above in combination with a program already recorded in the computer system.

[0084] Thus, the embodiment of this invention has been described together with the drawings, but specific configurations are not limited to the above-described embodiment and include various configurations that do not depart from the scope of the invention. List of reference symbols 1 servo press 10 Control device 100 control device 110 Control device 11 Control 12 drivers 13 Adjustment unit 14 Capture value detection unit 15 Reference acquisition value storage unit 16 Machining acquisition value storage unit 17 Correction value calculation unit 18 storage unit 19 Control unit 102 Control unit 112 Control unit 20 press main body 21 roll 22 volumes 23 Ball screw spindle 30 servo motor 31 encoders 33 Position detection unit 40 table 50 stamps 60 shaft 70 workpiece 80 linear encoder 101 Temperature recording unit 111 Threshold storage unit

Claims

[1] Servo press (1), comprising: a plunger (50) configured to move up and down; a servo motor (30) configured to move the plunger (50) up and down; an encoder (31) arranged on the servo motor (30); a plunger position detection unit (33) configured to detect a position of the plunger (50) based on an output signal from the encoder (31); a setting unit (13) configured to set a position condition for the plunger (50); a detection element (80) configured to detect a stop position of the plunger (50), wherein the detection element (80) is a linear encoder (80) arranged at the stop position of the plunger (50); a detection value detection unit (14) configured to detect a detection value of the detection element (80) at the stop position of the plunger (50); a reference detection value storage unit (15) configured to store the detection value detected by the detection value detection unit (14) before a series of machining operations on a workpiece (70); a machining detection value storage unit (16) configured to overwrite the detection value detected by the detection value detection unit (14) in the series of machining operations on the workpiece (70); a correction value calculation unit (17) configured to calculate a correction value based on a reference detection value in the reference detection value storage unit (15) and a machining detection value in the machining detection value storage unit (16); and a servo motor control unit (19) configured to control the servo motor (30) based on the plunger position detected by the plunger position detection unit (33), the set plunger position, and the correction value calculated by the correction value calculation unit (17), and a temperature sensor (101) configured to detect the temperature around the plunger (50), wherein the servo motor control unit (19), when temperature data detected based on a measured value of the temperature sensor (101) is greater than predetermined temperature data, transmits a signal instructing calculation of a correction value to the correction value calculation unit (17) and performs control of the servo motor (30) in a next machining cycle based on the ram position detected by the ram position detection unit (33), the set ram position, and the correction value calculated by the correction value calculation unit (17) at a time point when the ram (50) reaches the stop position. [2] Servo press (1) according to claim 1 comprising: a threshold value storage unit (111) configured to store a threshold value for a magnitude of the correction value, wherein, when the correction value calculated by the correction value calculation unit (17) is greater than the threshold value stored in the threshold value storage unit (111), the servo motor control unit (102) performs control of the servo motor (30) in a next machining cycle based on the ram position detected by the ram position detection unit (33), the set ram position, and the correction value calculated by the correction value calculation unit (17) at a time point when the ram (50) reaches the stop position. [3] Control method for a servo press (1), comprising: a plunger (50) configured to move up and down; a servo motor (30) configured to move the plunger (50) up and down; an encoder (31) arranged on the servo motor (30); a plunger position detection unit (33); a setting unit (13) configured to set a position condition for the plunger (50); a detection element (80) configured to detect a stop position of the plunger (50), wherein the detection element (80) is a linear encoder arranged at the stop position of the plunger (50); a detection value detection unit (14) configured to detect a detection value of the detection element (80) at the stop position of the plunger (50); a reference detection value storage unit (15); a machining detection value storage unit (16); a correction value calculation unit (17); and a servo motor control unit (102), and a temperature sensor (101) configured to detect the temperature around the plunger (50), the method comprising: a first step in which, before a series of machining operations on a workpiece (70), the servo motor control unit (102) moves the ram (50) to the stop position by controlling the servo motor (30) based on the ram position detected by the ram position detection unit (33) and the set ram position; a second step in which the detection value detection unit (14) detects the detection value of the detection element (80) at the stop position of the plunger (50) and stores the detected detection value in the reference detection value storage unit (15); a third step in which the detection value detection unit (14) detects the detection value of the detection element (80) at the stop position of the slide (50) in the series of machining operations and stores the detected detection value in the machining detection value storage unit (16); a fourth step in which the correction value calculation unit (17) calculates a correction value based on a reference detection value in the reference detection value storage unit (15) and a machining detection value in the machining detection value storage unit (16); and a fifth step in which the servo motor control unit (102) controls the servo motor (30) in a next processing on the basis of the ram position detected by the ram position detection unit (33), the set ram position and the correction value calculated by the correction value calculation unit (17), wherein the servo motor control unit (102), when temperature data detected based on a measured value of the temperature sensor (101) is greater than predetermined temperature data, transmits a signal instructing calculation of a correction value to the correction value calculation unit (17) and performs control of the servo motor (30) in a next machining cycle based on the ram position detected by the ram position detection unit (33), the set ram position, and the correction value calculated by the correction value calculation unit (17) at a time point when the ram (50) reaches the stop position. [4] Program causing a computer to execute a control method for a servo press (1), comprising: a plunger (50) configured to move up and down; a servo motor (30) configured to move the plunger (50) up and down; an encoder (31) arranged on the servo motor (30); a plunger position detection unit (33); a setting unit (13) configured to set a position condition for the plunger (50); a detection element (80) configured to detect a stop position of the plunger (50), wherein the detection element (80) is a linear encoder arranged at the stop position of the plunger (50); a detection value detection unit (14) configured to detect a detection value of the detection element (80) at the stop position of the plunger (50); a reference detection value storage unit (15); a machining detection value storage unit (16); a correction value calculation unit (17); and a servo motor control unit (102), and a temperature sensor (101) configured to detect the temperature around the plunger (50), wherein the program causes the computer to perform the method comprising: a first step in which, before a series of machining operations on a workpiece (70), the servo motor control unit (102) moves the ram (50) to the stop position by controlling the servo motor (30) based on the ram position detected by the ram position detection unit (33) and the set ram position; a second step in which the detection value detection unit (14) detects the detection value of the detection element (80) at the stop position of the plunger (50) and stores the detected detection value in the reference detection value storage unit (15); a third step in which the detection value detection unit (14) detects the detection value of the detection element (80) at the stop position of the slide (50) in the series of machining operations and stores the detected detection value in the machining detection value storage unit (16); a fourth step in which the correction value calculation unit (17) calculates a correction value based on a reference detection value in the reference detection value storage unit (15) and a machining detection value in the machining detection value storage unit (16); and a fifth step in which the servo motor control unit (102) controls the servo motor (30) during a next machining operation based on the ram position detected by the ram position detection unit (33), the set ram position, and the correction value calculated by the correction value calculation unit (17). wherein the servo motor control unit (102), when temperature data detected based on a measured value of the temperature sensor (101) is greater than predetermined temperature data, transmits a signal instructing calculation of a correction value to the correction value calculation unit (17) and performs control of the servo motor (30) in a next machining cycle based on the ram position detected by the ram position detection unit (33), the set ram position, and the correction value calculated by the correction value calculation unit (17) at a time point when the ram (50) reaches the stop position.

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