Molding machine

Abstract

To provide a molding machine capable of suppressing damage caused by timing belt breakage and suppressing erroneous detection of abnormalities.SOLUTION: A control device 30 detects an output torque Tm of a master motor 13 and an output torque Ts of a slave motor 23. When either the output torque Tm or the output torque Ts is in a range from 0 to a reference torque Tr, the control device 30 stops a rotation of the master motor 13 and the slave motor 23 if a difference between the output torque Tm and the output torque Ts is greater than a first allowable value. When the output torque Tm and the output torque Ts are greater than the reference torque Tr, the control device 30 stops the rotation of the master motor 13 and the slave motor 23 if the difference between the output torque Tm and the output torque Ts is greater than a second allowable value. A value greater than the first allowable value is set for the second allowable value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A molding machine has been proposed that uses multiple relatively inexpensive, small electric motors as the drive sources for the injection shaft and the movable die plate. Such a molding machine can combine the drive forces of multiple electric motors to obtain large power while keeping costs down.

[0003] For example, the injection molding machine disclosed in Patent Document 1 has a configuration in which multiple electric motors drive multiple ball screw mechanisms, and these ball screw mechanisms move a linear motion plate to which a screw is attached in the axial direction. The multiple electric motors are connected to their corresponding ball screw mechanisms via timing belts. This injection molding machine displays an abnormality on a display when the difference in operating state quantities (load current, etc.) of the multiple electric motors exceeds a tolerance value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-351776 Summary of the Invention [Problem to be solved by the invention]

[0005] If the timing belt breaks, differences in the operation of the electric motors and ball screw mechanisms may occur, causing the linear motion plate to tilt and potentially damaging the injection molding machine. For example, by reducing the tolerance, the time from when the timing belt breaks to when an abnormality is detected can be shortened, and the electric motors can be stopped immediately after the abnormality is detected, thereby minimizing damage to the injection molding machine. However, reducing the tolerance may result in erroneous detection of differences in the operational state quantities that occur during normal operation of the injection molding machine.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a molding machine that can prevent damage caused by timing belt breakage and can prevent erroneous detection of abnormalities. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the molding machine of the present invention is a molding machine having a plurality of drive devices, one linear motion member moved by the plurality of drive devices, and a control device, wherein each drive device has an electric motor, a conversion mechanism that converts rotational motion into linear motion, and a timing belt that transmits the rotation of the electric motor to the conversion mechanism, and the control device rotates the plurality of electric motors so that their respective rotational positions are the same, detects the output torque of the plurality of electric motors, and when one of the output torques of the plurality of electric motors is in a range from 0 to a reference value, stops the rotation of the plurality of electric motors if the difference in output torque of the plurality of electric motors is greater than a first allowable value, and when all of the output torques of the plurality of electric motors are greater than the reference value, stops the rotation of the plurality of electric motors if the difference in output torque of the plurality of electric motors is greater than a second allowable value that is greater than the first allowable value. [Effects of the Invention]

[0008] When the timing belt of one of the multiple drive devices breaks, the electric motor of that drive device runs idle, resulting in a very small output torque. Therefore, when one of the output torques of the multiple electric motors is small (between 0 and a reference value), it is highly likely that the timing belt has broken. In this case, by using a relatively small first allowable value to determine the difference in the output torques of the multiple electric motors, the time from when the timing belt breaks to when it is detected as an abnormality can be shortened. Furthermore, when all of the output torques of the multiple electric motors are large (greater than the reference value), it is highly likely that the timing belt has not broken. In this case, by using a relatively large second allowable value to determine the difference in the output torques of the multiple electric motors, it is possible to reduce false detection of an abnormality. Therefore, damage due to a timing belt break can be reduced and false detection of an abnormality can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a schematic configuration of an injection molding machine according to an embodiment of the present invention; [Figure 2] 2 is a functional block diagram showing a schematic configuration of a control device of the injection molding machine of FIG. 1. FIG. [Figure 3] 3 is a flowchart showing an example of a speed command signal output process in a speed command signal output unit included in the control device of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] An injection molding machine according to one embodiment of the present invention will be described below. The injection molding machine of this embodiment converts the rotation of multiple electric motors into linear motion to drive a single linearly moving member, and operates the multiple electric motors in synchronization so that their rotational positions are aligned.

[0011] 1 is a diagram showing a schematic configuration of an injection molding machine according to one embodiment of the present invention. As shown in Fig. 1, the injection molding machine 1 has a screw 5, a linear motion plate 6, a first driving unit 10, a second driving unit 20, and a control unit 30.

[0012] The screw 5 is housed in a heating cylinder (not shown). The screw 5 is rotatable about its axis and movable in the axial direction. The screw 5 is rotated about its axis by an electric motor (not shown). The screw 5 is fixed to a linearly moving plate 6. The linearly moving plate 6 is moved axially (left and right in FIG. 1) together with the screw 5. The screw 5 injects the molten resin in the heating cylinder into the cavity of a mold (not shown). The screw 5 is an injection axis and a linearly moving member.

[0013] The first driving device 10 includes a master motor 13 , a first driving pulley 14 , a first driven pulley 15 , a first timing belt 16 , and a first ball screw mechanism 17 .

[0014] The master motor 13 is an electric servo motor. The first drive pulley 14 is coaxially fixed to the output shaft of the master motor 13. A first timing belt 16 is stretched between the first drive pulley 14 and the first driven pulley 15. The first timing belt 16 transmits the rotation of the first drive pulley 14 to the first driven pulley 15.

[0015] The first ball screw mechanism 17 is a conversion mechanism that converts the rotational motion of the first driven pulley 15 into linear motion and transmits it to the linear motion plate 6. The first ball screw mechanism 17 has a first screw shaft 17a and a first nut member 17b. When the first screw shaft 17a rotates around its axis, the first nut member 17b moves in the axial direction. The first driven pulley 15 is coaxially fixed to the first screw shaft 17a. The linear motion plate 6 is fixed to the first nut member 17b.

[0016] The second driving device 20 includes a slave motor 23 , a second driving pulley 24 , a second driven pulley 25 , a second timing belt 26 , and a second ball screw mechanism 27 .

[0017] The slave motor 23 is an electric servo motor. The second drive pulley 24 is coaxially fixed to the output shaft of the slave motor 23. A second timing belt 26 is stretched between the second drive pulley 24 and the second driven pulley 25. The second timing belt 26 transmits the rotation of the second drive pulley 24 to the second driven pulley 25.

[0018] The second ball screw mechanism 27 is a conversion mechanism that converts the rotational motion of the second driven pulley 25 into linear motion and transmits it to the linear motion plate 6. The second ball screw mechanism 27 has a second screw shaft 27a and a second nut member 27b. When the second screw shaft 27a rotates around its axis, the second nut member 27b moves in the axial direction. The second driven pulley 25 is coaxially fixed to the second screw shaft 27a. The linear motion plate 6 is fixed to the second nut member 27b.

[0019] The master motor 13 is provided with a first encoder 13a. The first encoder 13a outputs a master motor position signal S2 indicating the rotational position of the master motor 13 (corresponding to the axial position of the first nut member 17b of the first ball screw mechanism 17). The slave motor 23 is provided with a second encoder 23a. The second encoder 23a outputs a slave motor position signal S5 indicating the rotational position of the slave motor 23 (corresponding to the axial position of the second nut member 27b of the second ball screw mechanism 27). In this embodiment, the master motor 13 and the slave motor 23 are servo motors of the same type. However, the master motor 13 and the slave motor 23 may be servo motors of different types.

[0020] In the injection molding machine 1, the control device 30 receives an original speed command signal S0 from an external higher-level device (not shown), thereby controlling the driving of the master motor 13 and the slave motor 23.

[0021] When the master motor 13 is driven, its rotation is transmitted to the first screw shaft 17a of the first ball screw mechanism 17 via the first drive pulley 14, the first timing belt 16 and the first driven pulley 15, and the rotational motion is converted into linear motion and transmitted to the linear plate 6 fixed to the first nut member 17b of the first ball screw mechanism 17.

[0022] Similarly, when the slave motor 23 is driven, its rotation is transmitted to the second screw shaft 27a of the second ball screw mechanism 27 via the second drive pulley 24, the second timing belt 26 and the second driven pulley 25, and the rotational motion is converted into linear motion and transmitted to the linear plate 6 fixed to the second nut member 27b of the second ball screw mechanism 27.

[0023] As a result, the screw 5 integrated with the linear motion plate 6 is driven by the master motor 13 and the slave motor 23 to move linearly.

[0024] The control device 30 is configured with, for example, a microcomputer for embedded devices equipped with a CPU, ROM, RAM, EEPROM, various I / O interfaces, etc. The control device 30 is responsible for controlling the entire injection molding machine 1, and controls the entire molding operation including, for example, the plasticizing operation, the injection operation, the mold opening / closing operation, the ejection operation, etc.

[0025] Fig. 2 is a functional block diagram showing a schematic configuration of a control device 30 included in the injection molding machine of this embodiment. As shown in Fig. 2, the control device 30 includes a first speed control unit 31, a second speed control unit 32, a calculator 33, a position deviation detection unit 34, an output torque detection unit 35, and a speed command signal output unit 37. The CPU of the microcomputer included in the control device 30 functions as each of these functional units by executing various programs stored in the ROM.

[0026] The first speed control unit 31 receives the speed command signal S1 from the speed command signal output unit 37 and the master motor position signal S2 output by the first encoder 13a. The first speed control unit 31 detects the actual speed Nm of the master motor 13 by differentiating the master motor position signal S2 with respect to time, and outputs a master motor speed control signal S3 to the master motor 13 so that this actual speed Nm becomes the command speed N indicated in the speed command signal S1. In other words, the first speed control unit 31 controls the master motor 13 so that the actual speed Nm becomes the command speed N indicated in the speed command signal S1 output by the speed command signal output unit 37.

[0027] The second speed control unit 32 receives the corrected speed command signal S4 from the calculator 33 and the slave motor position signal S5 output by the second encoder 23a. The second speed control unit 32 detects the actual speed Ns of the slave motor 23 by differentiating the slave motor position signal S5 with respect to time, and outputs a slave motor speed control signal S6 to the slave motor so that the actual speed Ns becomes the corrected speed Na indicated by the corrected speed command signal S4. The corrected speed Na is a speed obtained by correcting the command speed N. The second speed control unit 32 controls the slave motor 23 so that the actual speed Ns becomes a speed (corrected speed Na) corresponding to the command speed N indicated in the speed command signal S1 output by the speed command signal output unit 37.

[0028] The calculator 33 receives the speed command signal S1 and a position deviation signal S7 from the position deviation detection unit 34. Based on the deviation of the rotational position of the slave motor 23 from the rotational position of the master motor 13 indicated by the position deviation signal S7, the calculator 33 outputs a corrected speed command signal S4 (corrected speed Na) to the second speed control unit 32, which is obtained by correcting the speed command signal S1 (command speed N) so as to eliminate this deviation.

[0029] The position deviation detection unit 34 receives the master motor position signal S2 and the slave motor position signal S5, and outputs a position deviation signal S7 corresponding to the deviation of the slave motor position signal S5 from the master motor position signal S2 (i.e., the axial positional deviation between the first nut member 17b and the second nut member 27b) to the calculator 33. The calculator 33 and the position deviation detection unit 34 are used to rotate the master motor 13 and the slave motor 23 so that their respective rotational positions are the same.

[0030] The master motor speed control signal S3 and the slave motor speed control signal S6 are input to the output torque detection unit 35. The output torque detection unit 35 detects the output torque Tm of the master motor 13 based on the master motor speed control signal S3, and detects the output torque Ts of the slave motor 23 based on the slave motor speed control signal S6. The output torque detection unit 35 outputs an output torque signal S8 including the output torque Tm and the output torque Ts to the speed command signal output unit 37.

[0031] The speed command signal output unit 37 receives the original speed command signal S0 and the output torque signal S8 from an external higher-level device, and outputs a speed command signal S1 based on these input signals.

[0032] The speed command signal output unit 37 stores the reference torque Tr, the first allowable value Tp1, and the second allowable value Tp2, which are information used to determine the output torque signal S8 (output torque Tm, output torque Ts), in the ROM or EEPROM of the microcomputer.

[0033] The reference torque Tr is used to estimate a breakage of one of the first timing belt 16 of the first drive device 10 and the second timing belt 26 of the second drive device 20. When the first timing belt 16 breaks, the master motor 13 runs idle and the output torque Tm decreases. Similarly, when the second timing belt 26 breaks, the slave motor 23 runs idle and the output torque Ts decreases. The reference torque Tr is set based on the value that the output torque Tm of the master motor 13 can take when the first timing belt 16 breaks and the value that the output torque Ts of the slave motor 23 can take when the second timing belt 26 breaks. By appropriately setting the reference torque Tr, it can be estimated that one of the first timing belt 16 and the second timing belt 26 has broken when one of the output torque Tm and the output torque Ts is within the range from 0 to the reference torque Tr. When the output torque Tm and the output torque Ts are greater than the reference torque Tr, it can be assumed that there is no break in the first timing belt 16 and the second timing belt 26. The reference torque Tr is a reference value.

[0034] The first tolerance value Tp1 and the second tolerance value Tp2 are used to detect a difference in the operation of the first drive unit 10 and the second drive unit 20. When the first drive unit 10 and the second drive unit 20 are operating normally, the difference Td (Td = |Tm - Ts|) between the output torque Tm of the master motor 13 and the output torque Ts of the slave motor 23 is zero or a small difference. When a difference in the operation of the first drive unit 10 and the second drive unit 20 occurs due to some abnormality, the difference Td becomes large. The first tolerance value Tp1 is used to determine the difference Td when it is estimated that one of the first timing belt 16 and the second timing belt 26 is broken. The second tolerance value Tp2 is larger than the first tolerance value Tp1 and is used to determine the difference Td when it is estimated that the first timing belt 16 and the second timing belt 26 are not broken.

[0035] An example of speed command signal output processing in the speed command signal output unit 37 will be described with reference to the flowchart of Fig. 3. Fig. 3 is a flowchart showing an example of speed command signal output processing in the speed command signal output unit 37 of the control device 30.

[0036] The speed command signal output unit 37 acquires the original speed command signal S0 and the output torque signal S8 (T110, T120).

[0037] The speed command signal output unit 37 determines whether the output torque Tm of the master motor 13 included in the output torque signal S8 is equal to or less than the reference torque Tr (that is, 0≦Tm≦Tr). Similarly, it is determined whether the output torque Ts of the slave motor 23 is equal to or less than the reference torque Tr (that is, 0≦Ts≦Tr) (T130).

[0038] When the output torque Tm of the master motor 13 is equal to or less than the reference torque Tr, or when the output torque Ts of the slave motor 23 is equal to or less than the reference torque Tr (Y at T130), the speed command signal output unit 37 assumes that one of the first timing belt 16 and the second timing belt 26 has broken, and determines whether the difference Td between the output torque Tm and the output torque Ts is greater than a first allowable value Tp1 (T140).

[0039] When the difference Td between the output torque Tm and the output torque Ts is greater than the first allowable value Tp1 (Y at T140), the speed command signal output unit 37 determines that an abnormal difference has occurred in the operation of the first drive unit 10 and the second drive unit 20, and outputs a speed command signal S1 with a command speed N of 0 (T150). In other words, the speed command signal output unit 37 stops the rotation of the master motor 13 and the slave motor 23. Then, the current speed command signal output process ends. In determining the difference Td using the first allowable value Tp1, specifically, (i) the speed command signal output unit 37 determines that an abnormal difference has occurred in the operation of the first drive unit 10 and the second drive unit 20 when the difference Td remains greater than the first allowable value Tp1 for a predetermined time, and (ii) the speed command signal output unit 37 determines that there is no abnormal difference in the operation of the first drive unit 10 and the second drive unit 20 when the difference Td becomes equal to or less than the first allowable value Tp1 before the difference Td remains greater than the first allowable value Tp1 for the predetermined time.

[0040] When the difference Td between the output torque Tm and the output torque Ts is equal to or smaller than the first allowable value Tp1 (N at T140), the speed command signal output unit 37 determines that there is no abnormal difference between the operations of the first drive unit 10 and the second drive unit 20, and outputs a speed command signal S1 that sets the original speed No (original speed command value) indicated in the original speed command signal S0 as the command speed N (T160).Then, the current speed command signal output process ends, and the process proceeds to the next speed command signal output process.

[0041] When the output torque Tm of the master motor 13 is greater than the reference torque Tr and the output torque Ts of the slave motor 23 is greater than the reference torque Tr (N at T130), the speed command signal output unit 37 assumes that the first timing belt 16 and the second timing belt 26 are not broken, and determines whether the difference Td between the output torque Tm and the output torque Ts is greater than the second allowable value Tp2 (T170).

[0042] When the difference Td between the output torque Tm and the output torque Ts is greater than the second allowable value Tp2 (Y at T170), the speed command signal output unit 37 determines that an abnormal difference has occurred in the operations of the first drive unit 10 and the second drive unit 20, and outputs a speed command signal S1 with a command speed N of 0 (T150). In other words, the speed command signal output unit 37 stops the rotation of the master motor 13 and the slave motor 23. Then, the current speed command signal output process ends. Note that the speed command signal output unit 37 also performs the same processes as those in (i) and (ii) above when determining the difference Td using the second allowable value Tp2.

[0043] When the difference Td between the output torque Tm and the output torque Ts is equal to or smaller than the second allowable value Tp2 (N at T170), the speed command signal output unit 37 determines that there is no abnormal difference between the operations of the first drive unit 10 and the second drive unit 20, and outputs a speed command signal S1 that sets the original speed No (original speed command value) indicated in the original speed command signal S0 as the command speed N (T160).Then, the current speed command signal output process ends, and the process proceeds to the next speed command signal output process.

[0044] In the speed command signal output process, the output torque Tm of the master motor 13 detected by the output torque detection unit 35 is expressed as a percentage [%] of the rated torque of the master motor 13. The output torque Ts of the slave motor 23 detected by the output torque detection unit 35 is expressed as a percentage [%] of the rated torque of the slave motor 23. The reference torque Tr, the first allowable value Tp1, and the second allowable value Tp2 are also expressed as percentages [%] of the rated torque. The reference torque Tr is preferably 5 to 15%, and in this embodiment, the reference torque Tr is 10%. The second allowable value Tp2 is set to a value larger than the first allowable value Tp1. In this embodiment, the first allowable value Tp1 is 10%, and the second allowable value Tp2 is 200%. The reference torque Tr, the first allowable value Tp1, and the second allowable value Tp2 are set appropriately depending on the configuration of the injection molding machine 1, etc.

[0045] The output torque Tm of the master motor 13, the output torque Ts of the slave motor 23, the reference torque Tr, the first allowable value Tp1, and the second allowable value Tp2 may be values ​​other than percentages [%] of the rated torque, and may be, for example, absolute magnitude of torque or a current value corresponding to the magnitude of torque. In this specification, "torque" means information that directly or indirectly indicates torque (information related to torque).

[0046] The injection molding machine 1 of this embodiment includes a first drive unit 10, a second drive unit 20, a screw 5 moved by the first drive unit 10 and the second drive unit 20, and a control unit 30. The first drive unit 10 includes a master motor 13, a first ball screw mechanism 17, and a first timing belt 16 that transmits the rotation of the master motor 13 to the first ball screw mechanism 17. The second drive unit 20 includes a slave motor 23, a second ball screw mechanism 27, and a second timing belt 26 that transmits the rotation of the slave motor 23 to the second ball screw mechanism 27. The control unit 30 rotates the master motor 13 and the slave motor 23 so that their respective rotational positions are the same. The control unit 30 detects the output torque Tm of the master motor 13 and the output torque Ts of the slave motor 23. When one of the output torque Tm and the output torque Ts is in the range from 0 to the reference torque Tr, if the difference Td between the output torque Tm and the output torque Ts is greater than a first permissible value Tp1, the control device 30 stops the rotation of the master motor 13 and the slave motor 23. When the output torque Tm of the master motor 13 and the output torque Ts of the slave motor 23 are greater than the reference torque Tr, the control device 30 stops the rotation of the master motor 13 and the slave motor 23 if the difference Td between the output torque Tm and the output torque Ts is greater than a second permissible value Tp2 that is greater than the first permissible value Tp1.

[0047] When the first timing belt 16 of the first drive unit 10 breaks, the master motor 13 of the first drive unit 10 runs idle, resulting in a very small output torque Tm. When the second timing belt 26 of the second drive unit 20 breaks, the slave motor 23 of the second drive unit 20 runs idle, resulting in a very small output torque Ts. When the output torque Tm or the output torque Ts is small (between 0 and the reference torque Tr), it is highly likely that the first timing belt 16 or the second timing belt 26 has broken. In this case, by using the relatively small first allowable value Tp1 to determine the difference Td between the output torque Tm and the output torque Ts, the time from when the timing belt breaks to when it is detected as an abnormality can be shortened. This allows the operation of the first drive unit 10 and the second drive unit 20 to be stopped quickly after the timing belt breaks. Furthermore, when the output torque Tm and the output torque Ts are large (larger than the reference torque Tr), it is highly likely that the timing belt is not broken, and in this case, the relatively large second allowable value Tp2 is used to determine the difference Td, thereby preventing erroneous detection of an abnormality. Therefore, damage to the injection molding machine 1 due to a broken timing belt can be prevented, and erroneous detection of an abnormality can also be prevented.

[0048] In the above-described embodiment, there are two drive units (first drive unit 10 and second drive unit 20), but this is not limited to this, and the present invention can also be applied to a configuration having three or more drive units.

[0049] In addition, although the above-described embodiments have been described as an injection molding machine that injects a resin material into a mold, the present invention is not limited to this. The present invention can be applied to any molding machine or molding system that injects a material for a molded product into a mold, such as a die-casting machine that injects a metal material into a mold.

[0050] Although several embodiments of the present invention have been described above, the present invention is not limited to these examples. Any modifications to the above-described embodiments, such as additions, deletions, or design changes made by a person skilled in the art, or any combinations of features of the embodiments, are also included within the scope of the present invention as long as they include the gist of the present invention. [Explanation of symbols]

[0051] 1...injection molding machine, 5...screw, 6...linear plate, 10...first driving device, 13...master motor, 13a...first encoder, 14...first driving pulley, 15...first driven pulley, 16...first timing belt, 17...first ball screw mechanism, 17a...first screw shaft, 17b...first nut member, 20... second driving device, 23... slave motor, 23a... second encoder, 24... second driving pulley, 25... second driven pulley, 26... second timing belt, 27... second ball screw mechanism, 27a... second screw shaft, 27b... second nut member, 30...control device, 31...first speed control section, 32...second speed control section, 33...arithmetic unit, 34...position deviation detection section, 35...output torque detection section, 37...speed command signal output section, S0...original speed command signal, S1...speed command signal, S2...master motor position signal, S3...master motor speed control signal, S4...corrected speed command signal, S5...slave motor position signal, S6...slave motor speed control signal, S7...position deviation signal, S8...output torque signal, Tm, Ts...output torque, Td...difference, Tr...reference torque, Tp1...first tolerance, Tp2...second tolerance

Claims

[Claim 1] A molding machine having a plurality of drive devices, a linearly moving member moved by the plurality of drive devices, and a control device, Each drive device includes an electric motor, a conversion mechanism that converts rotational motion into linear motion, and a timing belt that transmits rotation of the electric motor to the conversion mechanism; The control device Rotating the plurality of electric motors so that their rotational positions are the same, Detecting output torques of the plurality of electric motors; When one of the output torques of the plurality of electric motors is in a range from 0 to a reference value, if a difference between the output torques of the plurality of electric motors is greater than a first allowable value, the rotation of the plurality of electric motors is stopped; a molding machine configured to stop rotation of the electric motors when a difference between the output torques of the electric motors is greater than a second allowable value that is greater than the first allowable value when all of the output torques of the electric motors are greater than the reference value.

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